Initial import of miette-derive-5.9.0 am: 437d15e784 am: af7096b4ab am: 330b5b06b3 am: b980cfea52

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/miette-derive/+/2638911 Change-Id: I426625c5d97881803cd0a0fd82892ecc5f5ac5b8 Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
author: Matthew Maurer <mmaurer@google.com> 2023-06-26 23:37:40 +0000
committer: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com> 2023-06-26 23:37:40 +0000
commit: cf18a0d3a3b53ce574de2906a5f82f89a77f1888 (patch)
tree: c82295365488871209366131d0b6d3708991d841
parent: 5d5fc11f1e70fa2ef447cf14a8f6f5acae51d2b4 (diff)
parent: b980cfea52a3e39940ec28c531f7e1d230f8c28a (diff)
download: miette-derive-cf18a0d3a3b53ce574de2906a5f82f89a77f1888.tar.gz
21 files changed, 2208 insertions, 0 deletions
diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
new file mode 100644
index 0000000..767945a
--- /dev/null
+++ b/.cargo_vcs_info.json
@@ -0,0 +1,6 @@
+{
+  "git": {
+    "sha1": "91e5f5b7e347b921921bac7135c56c600abb1fab"
+  },
+  "path_in_vcs": "miette-derive"
+}
+\ No newline at end of file
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..da6ab4c
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,31 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+name = "miette-derive"
+version = "5.9.0"
+authors = ["Kat Marchán <kzm@zkat.tech>"]
+description = "Derive macros for miette. Like `thiserror` for Diagnostics."
+license = "Apache-2.0"
+repository = "https://github.com/zkat/miette"
+
+[lib]
+proc-macro = true
+
+[dependencies.proc-macro2]
+version = "1.0"
+
+[dependencies.quote]
+version = "1.0"
+
+[dependencies.syn]
+version = "2.0.11"
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..461a328
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,16 @@
+[package]
+name = "miette-derive"
+version = "5.9.0"
+authors = ["Kat Marchán <kzm@zkat.tech>"]
+edition = "2018"
+license = "Apache-2.0"
+description = "Derive macros for miette. Like `thiserror` for Diagnostics."
+repository = "https://github.com/zkat/miette"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1.0"
+quote = "1.0"
+syn = "2.0.11"
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..10fa5cc
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,229 @@
+Apache License
+
+Version 2.0, January 2004
+
+http://www.apache.org/licenses/ TERMS
+AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
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+   1. Definitions.
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+license terms and conditions for use, reproduction, or distribution of Your
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+   5. Submission of Contributions. Unless You explicitly
+state otherwise, any Contribution intentionally submitted for inclusion in the
+Work by You to the Licensor shall be under the terms and conditions of this
+License, without any additional terms or conditions. Notwithstanding the above,
+nothing herein shall supersede or modify the terms of any separate license
+agreement you may have executed with Licensor regarding such Contributions.
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+6. Trademarks. This License does not grant permission to use the trade names,
+trademarks, service marks, or product names of the Licensor, except as required
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+   7. Disclaimer of Warranty. Unless
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+(and each Contributor provides its Contributions) on an "AS IS" BASIS, WITHOUT
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+by applicable law (such as deliberate and grossly negligent acts) or agreed to in
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+Work (including but not limited to damages for loss of goodwill, work stoppage,
+computer failure or malfunction, or any and all other commercial damages or
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+damages.
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+   9. Accepting Warranty or Additional Liability. While redistributing
+the Work or Derivative Works thereof, You may choose to offer, and charge a fee
+for, acceptance of support, warranty, indemnity, or other liability obligations
+and/or rights consistent with this License. However, in accepting such
+obligations, You may act only on Your own behalf and on Your sole responsibility,
+not on behalf of any other Contributor, and only if You agree to indemnify,
+defend, and hold each Contributor harmless for any liability incurred by, or
+claims asserted against, such Contributor by reason of your accepting any such
+warranty or additional liability. END OF TERMS AND CONDITIONS
+
+APPENDIX: How to
+apply the Apache License to your work.
+
+To apply the Apache License to your work,
+attach the following boilerplate notice, with the fields enclosed by brackets
+"[]" replaced with your own identifying information. (Don't include the
+brackets!) The text should be enclosed in the appropriate comment syntax for the
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+Copyright [yyyy] Kat
+Marchán
+
+Licensed under the Apache License, Version 2.0 (the "License");
+
+you may
+not use this file except in compliance with the License.
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+http://www.apache.org/licenses/LICENSE-2.0
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+\ No newline at end of file
diff --git a/METADATA b/METADATA
new file mode 100644
index 0000000..c8c8ea7
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,19 @@
+name: "miette-derive"
+description: "Derive macros for miette. Like `thiserror` for Diagnostics."
+third_party {
+  url {
+    type: HOMEPAGE
+    value: "https://crates.io/crates/miette-derive"
+  }
+  url {
+    type: ARCHIVE
+    value: "https://static.crates.io/crates/miette-derive/miette-derive-5.9.0.crate"
+  }
+  version: "5.9.0"
+  license_type: NOTICE
+  last_upgrade_date {
+    year: 2023
+    month: 6
+    day: 12
+  }
+}
diff --git a/MODULE_LICENSE_APACHE2 b/MODULE_LICENSE_APACHE2
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_APACHE2
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..45dc4dd
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1 @@
+include platform/prebuilts/rust:master:/OWNERS
diff --git a/src/code.rs b/src/code.rs
new file mode 100644
index 0000000..22dc795
--- /dev/null
+++ b/src/code.rs
@@ -0,0 +1,80 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{
+    parenthesized,
+    parse::{Parse, ParseStream},
+    Token,
+};
+
+use crate::{
+    diagnostic::{DiagnosticConcreteArgs, DiagnosticDef},
+    forward::WhichFn,
+    utils::gen_all_variants_with,
+};
+
+#[derive(Debug)]
+pub struct Code(pub String);
+
+impl Parse for Code {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let ident = input.parse::<syn::Ident>()?;
+        if ident == "code" {
+            let la = input.lookahead1();
+            if la.peek(syn::token::Paren) {
+                let content;
+                parenthesized!(content in input);
+                let la = content.lookahead1();
+                if la.peek(syn::LitStr) {
+                    let str = content.parse::<syn::LitStr>()?;
+                    Ok(Code(str.value()))
+                } else {
+                    let path = content.parse::<syn::Path>()?;
+                    Ok(Code(
+                        path.segments
+                            .iter()
+                            .map(|s| s.ident.to_string())
+                            .collect::<Vec<_>>()
+                            .join("::"),
+                    ))
+                }
+            } else {
+                input.parse::<Token![=]>()?;
+                Ok(Code(input.parse::<syn::LitStr>()?.value()))
+            }
+        } else {
+            Err(syn::Error::new(ident.span(), "diagnostic code is required. Use #[diagnostic(code = ...)] or #[diagnostic(code(...))] to define one."))
+        }
+    }
+}
+
+impl Code {
+    pub(crate) fn gen_enum(variants: &[DiagnosticDef]) -> Option<TokenStream> {
+        gen_all_variants_with(
+            variants,
+            WhichFn::Code,
+            |ident, fields, DiagnosticConcreteArgs { code, .. }| {
+                let code = &code.as_ref()?.0;
+                Some(match fields {
+                    syn::Fields::Named(_) => {
+                        quote! { Self::#ident { .. } => std::option::Option::Some(std::boxed::Box::new(#code)), }
+                    }
+                    syn::Fields::Unnamed(_) => {
+                        quote! { Self::#ident(..) => std::option::Option::Some(std::boxed::Box::new(#code)), }
+                    }
+                    syn::Fields::Unit => {
+                        quote! { Self::#ident => std::option::Option::Some(std::boxed::Box::new(#code)), }
+                    }
+                })
+            },
+        )
+    }
+
+    pub(crate) fn gen_struct(&self) -> Option<TokenStream> {
+        let code = &self.0;
+        Some(quote! {
+            fn code(&self) -> std::option::Option<std::boxed::Box<dyn std::fmt::Display + '_>> {
+                std::option::Option::Some(std::boxed::Box::new(#code))
+            }
+        })
+    }
+}
diff --git a/src/diagnostic.rs b/src/diagnostic.rs
new file mode 100644
index 0000000..0173d2a
--- /dev/null
+++ b/src/diagnostic.rs
@@ -0,0 +1,397 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{punctuated::Punctuated, DeriveInput, Token};
+
+use crate::code::Code;
+use crate::diagnostic_arg::DiagnosticArg;
+use crate::diagnostic_source::DiagnosticSource;
+use crate::forward::{Forward, WhichFn};
+use crate::help::Help;
+use crate::label::Labels;
+use crate::related::Related;
+use crate::severity::Severity;
+use crate::source_code::SourceCode;
+use crate::url::Url;
+
+pub enum Diagnostic {
+    Struct {
+        generics: syn::Generics,
+        ident: syn::Ident,
+        fields: syn::Fields,
+        args: DiagnosticDefArgs,
+    },
+    Enum {
+        ident: syn::Ident,
+        generics: syn::Generics,
+        variants: Vec<DiagnosticDef>,
+    },
+}
+
+pub struct DiagnosticDef {
+    pub ident: syn::Ident,
+    pub fields: syn::Fields,
+    pub args: DiagnosticDefArgs,
+}
+
+pub enum DiagnosticDefArgs {
+    Transparent(Forward),
+    Concrete(Box<DiagnosticConcreteArgs>),
+}
+
+impl DiagnosticDefArgs {
+    pub(crate) fn forward_or_override_enum(
+        &self,
+        variant: &syn::Ident,
+        which_fn: WhichFn,
+        mut f: impl FnMut(&DiagnosticConcreteArgs) -> Option<TokenStream>,
+    ) -> Option<TokenStream> {
+        match self {
+            Self::Transparent(forward) => Some(forward.gen_enum_match_arm(variant, which_fn)),
+            Self::Concrete(concrete) => f(concrete).or_else(|| {
+                concrete
+                    .forward
+                    .as_ref()
+                    .map(|forward| forward.gen_enum_match_arm(variant, which_fn))
+            }),
+        }
+    }
+}
+
+#[derive(Default)]
+pub struct DiagnosticConcreteArgs {
+    pub code: Option<Code>,
+    pub severity: Option<Severity>,
+    pub help: Option<Help>,
+    pub labels: Option<Labels>,
+    pub source_code: Option<SourceCode>,
+    pub url: Option<Url>,
+    pub forward: Option<Forward>,
+    pub related: Option<Related>,
+    pub diagnostic_source: Option<DiagnosticSource>,
+}
+
+impl DiagnosticConcreteArgs {
+    fn for_fields(fields: &syn::Fields) -> Result<Self, syn::Error> {
+        let labels = Labels::from_fields(fields)?;
+        let source_code = SourceCode::from_fields(fields)?;
+        let related = Related::from_fields(fields)?;
+        let help = Help::from_fields(fields)?;
+        let diagnostic_source = DiagnosticSource::from_fields(fields)?;
+        Ok(DiagnosticConcreteArgs {
+            code: None,
+            help,
+            related,
+            severity: None,
+            labels,
+            url: None,
+            forward: None,
+            source_code,
+            diagnostic_source,
+        })
+    }
+
+    fn add_args(
+        &mut self,
+        attr: &syn::Attribute,
+        args: impl Iterator<Item = DiagnosticArg>,
+        errors: &mut Vec<syn::Error>,
+    ) {
+        for arg in args {
+            match arg {
+                DiagnosticArg::Transparent => {
+                    errors.push(syn::Error::new_spanned(attr, "transparent not allowed"));
+                }
+                DiagnosticArg::Forward(to_field) => {
+                    if self.forward.is_some() {
+                        errors.push(syn::Error::new_spanned(
+                            attr,
+                            "forward has already been specified",
+                        ));
+                    }
+                    self.forward = Some(to_field);
+                }
+                DiagnosticArg::Code(new_code) => {
+                    if self.code.is_some() {
+                        errors.push(syn::Error::new_spanned(
+                            attr,
+                            "code has already been specified",
+                        ));
+                    }
+                    self.code = Some(new_code);
+                }
+                DiagnosticArg::Severity(sev) => {
+                    if self.severity.is_some() {
+                        errors.push(syn::Error::new_spanned(
+                            attr,
+                            "severity has already been specified",
+                        ));
+                    }
+                    self.severity = Some(sev);
+                }
+                DiagnosticArg::Help(hl) => {
+                    if self.help.is_some() {
+                        errors.push(syn::Error::new_spanned(
+                            attr,
+                            "help has already been specified",
+                        ));
+                    }
+                    self.help = Some(hl);
+                }
+                DiagnosticArg::Url(u) => {
+                    if self.url.is_some() {
+                        errors.push(syn::Error::new_spanned(
+                            attr,
+                            "url has already been specified",
+                        ));
+                    }
+                    self.url = Some(u);
+                }
+            }
+        }
+    }
+}
+
+impl DiagnosticDefArgs {
+    fn parse(
+        _ident: &syn::Ident,
+        fields: &syn::Fields,
+        attrs: &[&syn::Attribute],
+        allow_transparent: bool,
+    ) -> syn::Result<Self> {
+        let mut errors = Vec::new();
+
+        // Handle the only condition where Transparent is allowed
+        if allow_transparent && attrs.len() == 1 {
+            if let Ok(args) =
+                attrs[0].parse_args_with(Punctuated::<DiagnosticArg, Token![,]>::parse_terminated)
+            {
+                if matches!(args.first(), Some(DiagnosticArg::Transparent)) {
+                    let forward = Forward::for_transparent_field(fields)?;
+                    return Ok(Self::Transparent(forward));
+                }
+            }
+        }
+
+        // Create errors for any appearances of Transparent
+        let error_message = if allow_transparent {
+            "diagnostic(transparent) not allowed in combination with other args"
+        } else {
+            "diagnostic(transparent) not allowed here"
+        };
+        fn is_transparent(d: &DiagnosticArg) -> bool {
+            matches!(d, DiagnosticArg::Transparent)
+        }
+
+        let mut concrete = DiagnosticConcreteArgs::for_fields(fields)?;
+        for attr in attrs {
+            let args =
+                attr.parse_args_with(Punctuated::<DiagnosticArg, Token![,]>::parse_terminated);
+            let args = match args {
+                Ok(args) => args,
+                Err(error) => {
+                    errors.push(error);
+                    continue;
+                }
+            };
+
+            if args.iter().any(is_transparent) {
+                errors.push(syn::Error::new_spanned(attr, error_message));
+            }
+
+            let args = args
+                .into_iter()
+                .filter(|x| !matches!(x, DiagnosticArg::Transparent));
+
+            concrete.add_args(attr, args, &mut errors);
+        }
+
+        let combined_error = errors.into_iter().reduce(|mut lhs, rhs| {
+            lhs.combine(rhs);
+            lhs
+        });
+        if let Some(error) = combined_error {
+            Err(error)
+        } else {
+            Ok(DiagnosticDefArgs::Concrete(Box::new(concrete)))
+        }
+    }
+}
+
+impl Diagnostic {
+    pub fn from_derive_input(input: DeriveInput) -> Result<Self, syn::Error> {
+        let input_attrs = input
+            .attrs
+            .iter()
+            .filter(|x| x.path().is_ident("diagnostic"))
+            .collect::<Vec<&syn::Attribute>>();
+        Ok(match input.data {
+            syn::Data::Struct(data_struct) => {
+                let args = DiagnosticDefArgs::parse(
+                    &input.ident,
+                    &data_struct.fields,
+                    &input_attrs,
+                    true,
+                )?;
+
+                Diagnostic::Struct {
+                    fields: data_struct.fields,
+                    ident: input.ident,
+                    generics: input.generics,
+                    args,
+                }
+            }
+            syn::Data::Enum(syn::DataEnum { variants, .. }) => {
+                let mut vars = Vec::new();
+                for var in variants {
+                    let mut variant_attrs = input_attrs.clone();
+                    variant_attrs
+                        .extend(var.attrs.iter().filter(|x| x.path().is_ident("diagnostic")));
+                    let args =
+                        DiagnosticDefArgs::parse(&var.ident, &var.fields, &variant_attrs, true)?;
+                    vars.push(DiagnosticDef {
+                        ident: var.ident,
+                        fields: var.fields,
+                        args,
+                    });
+                }
+                Diagnostic::Enum {
+                    ident: input.ident,
+                    generics: input.generics,
+                    variants: vars,
+                }
+            }
+            syn::Data::Union(_) => {
+                return Err(syn::Error::new(
+                    input.ident.span(),
+                    "Can't derive Diagnostic for Unions",
+                ))
+            }
+        })
+    }
+
+    pub fn gen(&self) -> TokenStream {
+        match self {
+            Self::Struct {
+                ident,
+                fields,
+                generics,
+                args,
+            } => {
+                let (impl_generics, ty_generics, where_clause) = &generics.split_for_impl();
+                match args {
+                    DiagnosticDefArgs::Transparent(forward) => {
+                        let code_method = forward.gen_struct_method(WhichFn::Code);
+                        let help_method = forward.gen_struct_method(WhichFn::Help);
+                        let url_method = forward.gen_struct_method(WhichFn::Url);
+                        let labels_method = forward.gen_struct_method(WhichFn::Labels);
+                        let source_code_method = forward.gen_struct_method(WhichFn::SourceCode);
+                        let severity_method = forward.gen_struct_method(WhichFn::Severity);
+                        let related_method = forward.gen_struct_method(WhichFn::Related);
+                        let diagnostic_source_method =
+                            forward.gen_struct_method(WhichFn::DiagnosticSource);
+
+                        quote! {
+                            impl #impl_generics miette::Diagnostic for #ident #ty_generics #where_clause {
+                                #code_method
+                                #help_method
+                                #url_method
+                                #labels_method
+                                #severity_method
+                                #source_code_method
+                                #related_method
+                                #diagnostic_source_method
+                            }
+                        }
+                    }
+                    DiagnosticDefArgs::Concrete(concrete) => {
+                        let forward = |which| {
+                            concrete
+                                .forward
+                                .as_ref()
+                                .map(|fwd| fwd.gen_struct_method(which))
+                        };
+                        let code_body = concrete
+                            .code
+                            .as_ref()
+                            .and_then(|x| x.gen_struct())
+                            .or_else(|| forward(WhichFn::Code));
+                        let help_body = concrete
+                            .help
+                            .as_ref()
+                            .and_then(|x| x.gen_struct(fields))
+                            .or_else(|| forward(WhichFn::Help));
+                        let sev_body = concrete
+                            .severity
+                            .as_ref()
+                            .and_then(|x| x.gen_struct())
+                            .or_else(|| forward(WhichFn::Severity));
+                        let rel_body = concrete
+                            .related
+                            .as_ref()
+                            .and_then(|x| x.gen_struct())
+                            .or_else(|| forward(WhichFn::Related));
+                        let url_body = concrete
+                            .url
+                            .as_ref()
+                            .and_then(|x| x.gen_struct(ident, fields))
+                            .or_else(|| forward(WhichFn::Url));
+                        let labels_body = concrete
+                            .labels
+                            .as_ref()
+                            .and_then(|x| x.gen_struct(fields))
+                            .or_else(|| forward(WhichFn::Labels));
+                        let src_body = concrete
+                            .source_code
+                            .as_ref()
+                            .and_then(|x| x.gen_struct(fields))
+                            .or_else(|| forward(WhichFn::SourceCode));
+                        let diagnostic_source = concrete
+                            .diagnostic_source
+                            .as_ref()
+                            .and_then(|x| x.gen_struct())
+                            .or_else(|| forward(WhichFn::DiagnosticSource));
+                        quote! {
+                            impl #impl_generics miette::Diagnostic for #ident #ty_generics #where_clause {
+                                #code_body
+                                #help_body
+                                #sev_body
+                                #rel_body
+                                #url_body
+                                #labels_body
+                                #src_body
+                                #diagnostic_source
+                            }
+                        }
+                    }
+                }
+            }
+            Self::Enum {
+                ident,
+                generics,
+                variants,
+            } => {
+                let (impl_generics, ty_generics, where_clause) = &generics.split_for_impl();
+                let code_body = Code::gen_enum(variants);
+                let help_body = Help::gen_enum(variants);
+                let sev_body = Severity::gen_enum(variants);
+                let labels_body = Labels::gen_enum(variants);
+                let src_body = SourceCode::gen_enum(variants);
+                let rel_body = Related::gen_enum(variants);
+                let url_body = Url::gen_enum(ident, variants);
+                let diagnostic_source_body = DiagnosticSource::gen_enum(variants);
+                quote! {
+                    impl #impl_generics miette::Diagnostic for #ident #ty_generics #where_clause {
+                        #code_body
+                        #help_body
+                        #sev_body
+                        #labels_body
+                        #src_body
+                        #rel_body
+                        #url_body
+                        #diagnostic_source_body
+                    }
+                }
+            }
+        }
+    }
+}
diff --git a/src/diagnostic_arg.rs b/src/diagnostic_arg.rs
new file mode 100644
index 0000000..bade6f0
--- /dev/null
+++ b/src/diagnostic_arg.rs
@@ -0,0 +1,42 @@
+use syn::parse::{Parse, ParseStream};
+
+use crate::code::Code;
+use crate::forward::Forward;
+use crate::help::Help;
+use crate::severity::Severity;
+use crate::url::Url;
+
+pub enum DiagnosticArg {
+    Transparent,
+    Code(Code),
+    Severity(Severity),
+    Help(Help),
+    Url(Url),
+    Forward(Forward),
+}
+
+impl Parse for DiagnosticArg {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let ident = input.fork().parse::<syn::Ident>()?;
+        if ident == "transparent" {
+            // consume the token
+            let _: syn::Ident = input.parse()?;
+            Ok(DiagnosticArg::Transparent)
+        } else if ident == "forward" {
+            Ok(DiagnosticArg::Forward(input.parse()?))
+        } else if ident == "code" {
+            Ok(DiagnosticArg::Code(input.parse()?))
+        } else if ident == "severity" {
+            Ok(DiagnosticArg::Severity(input.parse()?))
+        } else if ident == "help" {
+            Ok(DiagnosticArg::Help(input.parse()?))
+        } else if ident == "url" {
+            Ok(DiagnosticArg::Url(input.parse()?))
+        } else {
+            Err(syn::Error::new(
+                ident.span(),
+                "Unrecognized diagnostic option",
+            ))
+        }
+    }
+}
diff --git a/src/diagnostic_source.rs b/src/diagnostic_source.rs
new file mode 100644
index 0000000..1104eb7
--- /dev/null
+++ b/src/diagnostic_source.rs
@@ -0,0 +1,78 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::spanned::Spanned;
+
+use crate::forward::WhichFn;
+use crate::{
+    diagnostic::{DiagnosticConcreteArgs, DiagnosticDef},
+    utils::{display_pat_members, gen_all_variants_with},
+};
+
+pub struct DiagnosticSource(syn::Member);
+
+impl DiagnosticSource {
+    pub(crate) fn from_fields(fields: &syn::Fields) -> syn::Result<Option<Self>> {
+        match fields {
+            syn::Fields::Named(named) => Self::from_fields_vec(named.named.iter().collect()),
+            syn::Fields::Unnamed(unnamed) => {
+                Self::from_fields_vec(unnamed.unnamed.iter().collect())
+            }
+            syn::Fields::Unit => Ok(None),
+        }
+    }
+
+    fn from_fields_vec(fields: Vec<&syn::Field>) -> syn::Result<Option<Self>> {
+        for (i, field) in fields.iter().enumerate() {
+            for attr in &field.attrs {
+                if attr.path().is_ident("diagnostic_source") {
+                    let diagnostic_source = if let Some(ident) = field.ident.clone() {
+                        syn::Member::Named(ident)
+                    } else {
+                        syn::Member::Unnamed(syn::Index {
+                            index: i as u32,
+                            span: field.span(),
+                        })
+                    };
+                    return Ok(Some(DiagnosticSource(diagnostic_source)));
+                }
+            }
+        }
+        Ok(None)
+    }
+
+    pub(crate) fn gen_enum(variants: &[DiagnosticDef]) -> Option<TokenStream> {
+        gen_all_variants_with(
+            variants,
+            WhichFn::DiagnosticSource,
+            |ident,
+             fields,
+             DiagnosticConcreteArgs {
+                 diagnostic_source, ..
+             }| {
+                let (display_pat, _display_members) = display_pat_members(fields);
+                diagnostic_source.as_ref().map(|diagnostic_source| {
+                    let rel = match &diagnostic_source.0 {
+                        syn::Member::Named(ident) => ident.clone(),
+                        syn::Member::Unnamed(syn::Index { index, .. }) => {
+                            quote::format_ident!("_{}", index)
+                        }
+                    };
+                    quote! {
+                        Self::#ident #display_pat => {
+                            std::option::Option::Some(std::borrow::Borrow::borrow(#rel))
+                        }
+                    }
+                })
+            },
+        )
+    }
+
+    pub(crate) fn gen_struct(&self) -> Option<TokenStream> {
+        let rel = &self.0;
+        Some(quote! {
+            fn diagnostic_source<'a>(&'a self) -> std::option::Option<&'a dyn miette::Diagnostic> {
+                std::option::Option::Some(std::borrow::Borrow::borrow(&self.#rel))
+            }
+        })
+    }
+}
diff --git a/src/fmt.rs b/src/fmt.rs
new file mode 100644
index 0000000..692c5ad
--- /dev/null
+++ b/src/fmt.rs
@@ -0,0 +1,235 @@
+// NOTE: Most code in this file is taken straight from `thiserror`.
+use std::collections::HashSet as Set;
+use std::iter::FromIterator;
+
+use proc_macro2::{Delimiter, Group, TokenStream, TokenTree};
+use quote::{format_ident, quote, quote_spanned, ToTokens};
+use syn::ext::IdentExt;
+use syn::parse::{ParseStream, Parser};
+use syn::{braced, bracketed, parenthesized, Ident, Index, LitStr, Member, Result, Token};
+
+#[derive(Clone)]
+pub struct Display {
+    pub fmt: LitStr,
+    pub args: TokenStream,
+    pub has_bonus_display: bool,
+}
+
+impl ToTokens for Display {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        let fmt = &self.fmt;
+        let args = &self.args;
+        tokens.extend(quote! {
+            write!(__formatter, #fmt #args)
+        });
+    }
+}
+
+impl Display {
+    // Transform `"error {var}"` to `"error {}", var`.
+    pub fn expand_shorthand(&mut self, members: &Set<Member>) {
+        let raw_args = self.args.clone();
+        let mut named_args = explicit_named_args.parse2(raw_args).unwrap();
+
+        let span = self.fmt.span();
+        let fmt = self.fmt.value();
+        let mut read = fmt.as_str();
+        let mut out = String::new();
+        let mut args = self.args.clone();
+        let mut has_bonus_display = false;
+
+        let mut has_trailing_comma = false;
+        if let Some(TokenTree::Punct(punct)) = args.clone().into_iter().last() {
+            if punct.as_char() == ',' {
+                has_trailing_comma = true;
+            }
+        }
+
+        while let Some(brace) = read.find('{') {
+            out += &read[..brace + 1];
+            read = &read[brace + 1..];
+            if read.starts_with('{') {
+                out.push('{');
+                read = &read[1..];
+                continue;
+            }
+            let next = match read.chars().next() {
+                Some(next) => next,
+                None => return,
+            };
+            let member = match next {
+                '0'..='9' => {
+                    let int = take_int(&mut read);
+                    let member = match int.parse::<u32>() {
+                        Ok(index) => Member::Unnamed(Index { index, span }),
+                        Err(_) => return,
+                    };
+                    if !members.contains(&member) {
+                        out += &int;
+                        continue;
+                    }
+                    member
+                }
+                'a'..='z' | 'A'..='Z' | '_' => {
+                    let mut ident = take_ident(&mut read);
+                    ident.set_span(span);
+                    Member::Named(ident)
+                }
+                _ => continue,
+            };
+            let local = match &member {
+                Member::Unnamed(index) => format_ident!("_{}", index),
+                Member::Named(ident) => ident.clone(),
+            };
+            let mut formatvar = local.clone();
+            if formatvar.to_string().starts_with("r#") {
+                formatvar = format_ident!("r_{}", formatvar);
+            }
+            if formatvar.to_string().starts_with('_') {
+                // Work around leading underscore being rejected by 1.40 and
+                // older compilers. https://github.com/rust-lang/rust/pull/66847
+                formatvar = format_ident!("field_{}", formatvar);
+            }
+            out += &formatvar.to_string();
+            if !named_args.insert(formatvar.clone()) {
+                // Already specified in the format argument list.
+                continue;
+            }
+            if !has_trailing_comma {
+                args.extend(quote_spanned!(span=> ,));
+            }
+            args.extend(quote_spanned!(span=> #formatvar = #local));
+            if read.starts_with('}') && members.contains(&member) {
+                has_bonus_display = true;
+                // args.extend(quote_spanned!(span=> .as_display()));
+            }
+            has_trailing_comma = false;
+        }
+
+        out += read;
+        self.fmt = LitStr::new(&out, self.fmt.span());
+        self.args = args;
+        self.has_bonus_display = has_bonus_display;
+    }
+}
+
+fn explicit_named_args(input: ParseStream) -> Result<Set<Ident>> {
+    let mut named_args = Set::new();
+
+    while !input.is_empty() {
+        if input.peek(Token![,]) && input.peek2(Ident::peek_any) && input.peek3(Token![=]) {
+            input.parse::<Token![,]>()?;
+            let ident = input.call(Ident::parse_any)?;
+            input.parse::<Token![=]>()?;
+            named_args.insert(ident);
+        } else {
+            input.parse::<TokenTree>()?;
+        }
+    }
+
+    Ok(named_args)
+}
+
+fn take_int(read: &mut &str) -> String {
+    let mut int = String::new();
+    for (i, ch) in read.char_indices() {
+        match ch {
+            '0'..='9' => int.push(ch),
+            _ => {
+                *read = &read[i..];
+                break;
+            }
+        }
+    }
+    int
+}
+
+fn take_ident(read: &mut &str) -> Ident {
+    let mut ident = String::new();
+    let raw = read.starts_with("r#");
+    if raw {
+        ident.push_str("r#");
+        *read = &read[2..];
+    }
+    for (i, ch) in read.char_indices() {
+        match ch {
+            'a'..='z' | 'A'..='Z' | '0'..='9' | '_' => ident.push(ch),
+            _ => {
+                *read = &read[i..];
+                break;
+            }
+        }
+    }
+    Ident::parse_any.parse_str(&ident).unwrap()
+}
+
+pub fn parse_token_expr(input: ParseStream, mut begin_expr: bool) -> Result<TokenStream> {
+    let mut tokens = Vec::new();
+    while !input.is_empty() {
+        if begin_expr && input.peek(Token![.]) {
+            if input.peek2(Ident) {
+                input.parse::<Token![.]>()?;
+                begin_expr = false;
+                continue;
+            }
+            if input.peek2(syn::LitInt) {
+                input.parse::<Token![.]>()?;
+                let int: Index = input.parse()?;
+                let ident = format_ident!("_{}", int.index, span = int.span);
+                tokens.push(TokenTree::Ident(ident));
+                begin_expr = false;
+                continue;
+            }
+        }
+
+        begin_expr = input.peek(Token![break])
+            || input.peek(Token![continue])
+            || input.peek(Token![if])
+            || input.peek(Token![in])
+            || input.peek(Token![match])
+            || input.peek(Token![mut])
+            || input.peek(Token![return])
+            || input.peek(Token![while])
+            || input.peek(Token![+])
+            || input.peek(Token![&])
+            || input.peek(Token![!])
+            || input.peek(Token![^])
+            || input.peek(Token![,])
+            || input.peek(Token![/])
+            || input.peek(Token![=])
+            || input.peek(Token![>])
+            || input.peek(Token![<])
+            || input.peek(Token![|])
+            || input.peek(Token![%])
+            || input.peek(Token![;])
+            || input.peek(Token![*])
+            || input.peek(Token![-]);
+
+        let token: TokenTree = if input.peek(syn::token::Paren) {
+            let content;
+            let delimiter = parenthesized!(content in input);
+            let nested = parse_token_expr(&content, true)?;
+            let mut group = Group::new(Delimiter::Parenthesis, nested);
+            group.set_span(delimiter.span.join());
+            TokenTree::Group(group)
+        } else if input.peek(syn::token::Brace) {
+            let content;
+            let delimiter = braced!(content in input);
+            let nested = parse_token_expr(&content, true)?;
+            let mut group = Group::new(Delimiter::Brace, nested);
+            group.set_span(delimiter.span.join());
+            TokenTree::Group(group)
+        } else if input.peek(syn::token::Bracket) {
+            let content;
+            let delimiter = bracketed!(content in input);
+            let nested = parse_token_expr(&content, true)?;
+            let mut group = Group::new(Delimiter::Bracket, nested);
+            group.set_span(delimiter.span.join());
+            TokenTree::Group(group)
+        } else {
+            input.parse()?
+        };
+        tokens.push(token);
+    }
+    Ok(TokenStream::from_iter(tokens))
+}
diff --git a/src/forward.rs b/src/forward.rs
new file mode 100644
index 0000000..171019a
--- /dev/null
+++ b/src/forward.rs
@@ -0,0 +1,161 @@
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote};
+use syn::{
+    parenthesized,
+    parse::{Parse, ParseStream},
+    spanned::Spanned,
+};
+
+pub enum Forward {
+    Unnamed(usize),
+    Named(syn::Ident),
+}
+
+impl Parse for Forward {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let forward = input.parse::<syn::Ident>()?;
+        if forward != "forward" {
+            return Err(syn::Error::new(forward.span(), "msg"));
+        }
+        let content;
+        parenthesized!(content in input);
+        let looky = content.lookahead1();
+        if looky.peek(syn::LitInt) {
+            let int: syn::LitInt = content.parse()?;
+            let index = int.base10_parse()?;
+            return Ok(Forward::Unnamed(index));
+        }
+        Ok(Forward::Named(content.parse()?))
+    }
+}
+
+#[derive(Copy, Clone)]
+pub enum WhichFn {
+    Code,
+    Help,
+    Url,
+    Severity,
+    Labels,
+    SourceCode,
+    Related,
+    DiagnosticSource,
+}
+
+impl WhichFn {
+    pub fn method_call(&self) -> TokenStream {
+        match self {
+            Self::Code => quote! { code() },
+            Self::Help => quote! { help() },
+            Self::Url => quote! { url() },
+            Self::Severity => quote! { severity() },
+            Self::Labels => quote! { labels() },
+            Self::SourceCode => quote! { source_code() },
+            Self::Related => quote! { related() },
+            Self::DiagnosticSource => quote! { diagnostic_source() },
+        }
+    }
+
+    pub fn signature(&self) -> TokenStream {
+        match self {
+            Self::Code => quote! {
+                fn code(& self) -> std::option::Option<std::boxed::Box<dyn std::fmt::Display + '_>>
+            },
+            Self::Help => quote! {
+                fn help(& self) -> std::option::Option<std::boxed::Box<dyn std::fmt::Display + '_>>
+            },
+            Self::Url => quote! {
+                fn url(& self) -> std::option::Option<std::boxed::Box<dyn std::fmt::Display + '_>>
+            },
+            Self::Severity => quote! {
+                fn severity(&self) -> std::option::Option<miette::Severity>
+            },
+            Self::Related => quote! {
+                fn related(&self) -> std::option::Option<std::boxed::Box<dyn std::iter::Iterator<Item = &dyn miette::Diagnostic> + '_>>
+            },
+            Self::Labels => quote! {
+                fn labels(&self) -> std::option::Option<std::boxed::Box<dyn std::iter::Iterator<Item = miette::LabeledSpan> + '_>>
+            },
+            Self::SourceCode => quote! {
+                fn source_code(&self) -> std::option::Option<&dyn miette::SourceCode>
+            },
+            Self::DiagnosticSource => quote! {
+                fn diagnostic_source(&self) -> std::option::Option<&dyn miette::Diagnostic>
+            },
+        }
+    }
+
+    pub fn catchall_arm(&self) -> TokenStream {
+        quote! { _ => std::option::Option::None }
+    }
+}
+
+impl Forward {
+    pub fn for_transparent_field(fields: &syn::Fields) -> syn::Result<Self> {
+        let make_err = || {
+            syn::Error::new(
+                fields.span(),
+                "you can only use #[diagnostic(transparent)] with exactly one field",
+            )
+        };
+        match fields {
+            syn::Fields::Named(named) => {
+                let mut iter = named.named.iter();
+                let field = iter.next().ok_or_else(make_err)?;
+                if iter.next().is_some() {
+                    return Err(make_err());
+                }
+                let field_name = field
+                    .ident
+                    .clone()
+                    .unwrap_or_else(|| format_ident!("unnamed"));
+                Ok(Self::Named(field_name))
+            }
+            syn::Fields::Unnamed(unnamed) => {
+                if unnamed.unnamed.iter().len() != 1 {
+                    return Err(make_err());
+                }
+                Ok(Self::Unnamed(0))
+            }
+            _ => Err(syn::Error::new(
+                fields.span(),
+                "you cannot use #[diagnostic(transparent)] with a unit struct or a unit variant",
+            )),
+        }
+    }
+
+    pub fn gen_struct_method(&self, which_fn: WhichFn) -> TokenStream {
+        let signature = which_fn.signature();
+        let method_call = which_fn.method_call();
+
+        let field_name = match self {
+            Forward::Named(field_name) => quote!(#field_name),
+            Forward::Unnamed(index) => {
+                let index = syn::Index::from(*index);
+                quote!(#index)
+            }
+        };
+
+        quote! {
+            #[inline]
+            #signature {
+                self.#field_name.#method_call
+            }
+        }
+    }
+
+    pub fn gen_enum_match_arm(&self, variant: &syn::Ident, which_fn: WhichFn) -> TokenStream {
+        let method_call = which_fn.method_call();
+        match self {
+            Forward::Named(field_name) => quote! {
+                Self::#variant { #field_name, .. } => #field_name.#method_call,
+            },
+            Forward::Unnamed(index) => {
+                let underscores: Vec<_> = core::iter::repeat(quote! { _, }).take(*index).collect();
+                let unnamed = format_ident!("unnamed");
+                quote! {
+                    Self::#variant ( #(#underscores)* #unnamed, .. ) => #unnamed.#method_call,
+                }
+            }
+        }
+    }
+}
diff --git a/src/help.rs b/src/help.rs
new file mode 100644
index 0000000..1c21054
--- /dev/null
+++ b/src/help.rs
@@ -0,0 +1,146 @@
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote};
+use syn::{
+    parenthesized,
+    parse::{Parse, ParseStream},
+    spanned::Spanned,
+    Fields, Token,
+};
+
+use crate::{
+    diagnostic::{DiagnosticConcreteArgs, DiagnosticDef},
+    utils::{display_pat_members, gen_all_variants_with},
+};
+use crate::{
+    fmt::{self, Display},
+    forward::WhichFn,
+};
+
+pub enum Help {
+    Display(Display),
+    Field(syn::Member, Box<syn::Type>),
+}
+
+impl Parse for Help {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let ident = input.parse::<syn::Ident>()?;
+        if ident == "help" {
+            let la = input.lookahead1();
+            if la.peek(syn::token::Paren) {
+                let content;
+                parenthesized!(content in input);
+                let fmt = content.parse()?;
+                let args = if content.is_empty() {
+                    TokenStream::new()
+                } else {
+                    fmt::parse_token_expr(&content, false)?
+                };
+                let display = Display {
+                    fmt,
+                    args,
+                    has_bonus_display: false,
+                };
+                Ok(Help::Display(display))
+            } else {
+                input.parse::<Token![=]>()?;
+                Ok(Help::Display(Display {
+                    fmt: input.parse()?,
+                    args: TokenStream::new(),
+                    has_bonus_display: false,
+                }))
+            }
+        } else {
+            Err(syn::Error::new(ident.span(), "not a help"))
+        }
+    }
+}
+
+impl Help {
+    pub(crate) fn from_fields(fields: &syn::Fields) -> syn::Result<Option<Self>> {
+        match fields {
+            syn::Fields::Named(named) => Self::from_fields_vec(named.named.iter().collect()),
+            syn::Fields::Unnamed(unnamed) => {
+                Self::from_fields_vec(unnamed.unnamed.iter().collect())
+            }
+            syn::Fields::Unit => Ok(None),
+        }
+    }
+
+    fn from_fields_vec(fields: Vec<&syn::Field>) -> syn::Result<Option<Self>> {
+        for (i, field) in fields.iter().enumerate() {
+            for attr in &field.attrs {
+                if attr.path().is_ident("help") {
+                    let help = if let Some(ident) = field.ident.clone() {
+                        syn::Member::Named(ident)
+                    } else {
+                        syn::Member::Unnamed(syn::Index {
+                            index: i as u32,
+                            span: field.span(),
+                        })
+                    };
+                    return Ok(Some(Help::Field(help, Box::new(field.ty.clone()))));
+                }
+            }
+        }
+        Ok(None)
+    }
+    pub(crate) fn gen_enum(variants: &[DiagnosticDef]) -> Option<TokenStream> {
+        gen_all_variants_with(
+            variants,
+            WhichFn::Help,
+            |ident, fields, DiagnosticConcreteArgs { help, .. }| {
+                let (display_pat, display_members) = display_pat_members(fields);
+                match &help.as_ref()? {
+                    Help::Display(display) => {
+                        let (fmt, args) = display.expand_shorthand_cloned(&display_members);
+                        Some(quote! {
+                            Self::#ident #display_pat => std::option::Option::Some(std::boxed::Box::new(format!(#fmt #args))),
+                        })
+                    }
+                    Help::Field(member, ty) => {
+                        let help = match &member {
+                            syn::Member::Named(ident) => ident.clone(),
+                            syn::Member::Unnamed(syn::Index { index, .. }) => {
+                                format_ident!("_{}", index)
+                            }
+                        };
+                        let var = quote! { __miette_internal_var };
+                        Some(quote! {
+                            Self::#ident #display_pat => {
+                                use miette::macro_helpers::ToOption;
+                                miette::macro_helpers::OptionalWrapper::<#ty>::new().to_option(&#help).as_ref().map(|#var| -> std::boxed::Box<dyn std::fmt::Display + '_> { std::boxed::Box::new(format!("{}", #var)) })
+                            },
+                        })
+                    }
+                }
+            },
+        )
+    }
+
+    pub(crate) fn gen_struct(&self, fields: &Fields) -> Option<TokenStream> {
+        let (display_pat, display_members) = display_pat_members(fields);
+        match self {
+            Help::Display(display) => {
+                let (fmt, args) = display.expand_shorthand_cloned(&display_members);
+                Some(quote! {
+                    fn help(&self) -> std::option::Option<std::boxed::Box<dyn std::fmt::Display + '_>> {
+                        #[allow(unused_variables, deprecated)]
+                        let Self #display_pat = self;
+                        std::option::Option::Some(std::boxed::Box::new(format!(#fmt #args)))
+                    }
+                })
+            }
+            Help::Field(member, ty) => {
+                let var = quote! { __miette_internal_var };
+                Some(quote! {
+                    fn help(&self) -> std::option::Option<std::boxed::Box<dyn std::fmt::Display + '_>> {
+                        #[allow(unused_variables, deprecated)]
+                        let Self #display_pat = self;
+                        use miette::macro_helpers::ToOption;
+                        miette::macro_helpers::OptionalWrapper::<#ty>::new().to_option(&self.#member).as_ref().map(|#var| -> std::boxed::Box<dyn std::fmt::Display + '_> { std::boxed::Box::new(format!("{}", #var)) })
+                    }
+                })
+            }
+        }
+    }
+}
diff --git a/src/label.rs b/src/label.rs
new file mode 100644
index 0000000..e0bc70a
--- /dev/null
+++ b/src/label.rs
@@ -0,0 +1,207 @@
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote};
+use syn::{
+    parenthesized,
+    parse::{Parse, ParseStream},
+    spanned::Spanned,
+    Token,
+};
+
+use crate::{
+    diagnostic::{DiagnosticConcreteArgs, DiagnosticDef},
+    fmt::{self, Display},
+    forward::WhichFn,
+    utils::{display_pat_members, gen_all_variants_with},
+};
+
+pub struct Labels(Vec<Label>);
+
+struct Label {
+    label: Option<Display>,
+    ty: syn::Type,
+    span: syn::Member,
+}
+
+struct LabelAttr {
+    label: Option<Display>,
+}
+
+impl Parse for LabelAttr {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        // Skip a token.
+        // This should receive one of:
+        // - label = "..."
+        // - label("...")
+        let _ = input.step(|cursor| {
+            if let Some((_, next)) = cursor.token_tree() {
+                Ok(((), next))
+            } else {
+                Err(cursor.error("unexpected empty attribute"))
+            }
+        });
+        let la = input.lookahead1();
+        let label = if la.peek(syn::token::Paren) {
+            // #[label("{}", x)]
+            let content;
+            parenthesized!(content in input);
+            if content.peek(syn::LitStr) {
+                let fmt = content.parse()?;
+                let args = if content.is_empty() {
+                    TokenStream::new()
+                } else {
+                    fmt::parse_token_expr(&content, false)?
+                };
+                let display = Display {
+                    fmt,
+                    args,
+                    has_bonus_display: false,
+                };
+                Some(display)
+            } else {
+                return Err(syn::Error::new(input.span(), "Invalid argument to label() attribute. The first argument must be a literal string."));
+            }
+        } else if la.peek(Token![=]) {
+            // #[label = "blabla"]
+            input.parse::<Token![=]>()?;
+            Some(Display {
+                fmt: input.parse()?,
+                args: TokenStream::new(),
+                has_bonus_display: false,
+            })
+        } else {
+            None
+        };
+        Ok(LabelAttr { label })
+    }
+}
+
+impl Labels {
+    pub fn from_fields(fields: &syn::Fields) -> syn::Result<Option<Self>> {
+        match fields {
+            syn::Fields::Named(named) => Self::from_fields_vec(named.named.iter().collect()),
+            syn::Fields::Unnamed(unnamed) => {
+                Self::from_fields_vec(unnamed.unnamed.iter().collect())
+            }
+            syn::Fields::Unit => Ok(None),
+        }
+    }
+
+    fn from_fields_vec(fields: Vec<&syn::Field>) -> syn::Result<Option<Self>> {
+        let mut labels = Vec::new();
+        for (i, field) in fields.iter().enumerate() {
+            for attr in &field.attrs {
+                if attr.path().is_ident("label") {
+                    let span = if let Some(ident) = field.ident.clone() {
+                        syn::Member::Named(ident)
+                    } else {
+                        syn::Member::Unnamed(syn::Index {
+                            index: i as u32,
+                            span: field.span(),
+                        })
+                    };
+                    use quote::ToTokens;
+                    let LabelAttr { label } =
+                        syn::parse2::<LabelAttr>(attr.meta.to_token_stream())?;
+                    labels.push(Label {
+                        label,
+                        span,
+                        ty: field.ty.clone(),
+                    });
+                }
+            }
+        }
+        if labels.is_empty() {
+            Ok(None)
+        } else {
+            Ok(Some(Labels(labels)))
+        }
+    }
+
+    pub(crate) fn gen_struct(&self, fields: &syn::Fields) -> Option<TokenStream> {
+        let (display_pat, display_members) = display_pat_members(fields);
+        let labels = self.0.iter().map(|highlight| {
+            let Label { span, label, ty } = highlight;
+            let var = quote! { __miette_internal_var };
+            if let Some(display) = label {
+                let (fmt, args) = display.expand_shorthand_cloned(&display_members);
+                quote! {
+                    miette::macro_helpers::OptionalWrapper::<#ty>::new().to_option(&self.#span)
+                    .map(|#var| miette::LabeledSpan::new_with_span(
+                        std::option::Option::Some(format!(#fmt #args)),
+                        #var.clone(),
+                    ))
+                }
+            } else {
+                quote! {
+                    miette::macro_helpers::OptionalWrapper::<#ty>::new().to_option(&self.#span)
+                    .map(|#var| miette::LabeledSpan::new_with_span(
+                        std::option::Option::None,
+                        #var.clone(),
+                    ))
+                }
+            }
+        });
+        Some(quote! {
+            #[allow(unused_variables)]
+            fn labels(&self) -> std::option::Option<std::boxed::Box<dyn std::iter::Iterator<Item = miette::LabeledSpan> + '_>> {
+                use miette::macro_helpers::ToOption;
+                let Self #display_pat = self;
+                std::option::Option::Some(Box::new(vec![
+                    #(#labels),*
+                ].into_iter().filter(Option::is_some).map(Option::unwrap)))
+            }
+        })
+    }
+
+    pub(crate) fn gen_enum(variants: &[DiagnosticDef]) -> Option<TokenStream> {
+        gen_all_variants_with(
+            variants,
+            WhichFn::Labels,
+            |ident, fields, DiagnosticConcreteArgs { labels, .. }| {
+                let (display_pat, display_members) = display_pat_members(fields);
+                labels.as_ref().and_then(|labels| {
+                    let variant_labels = labels.0.iter().map(|label| {
+                        let Label { span, label, ty } = label;
+                        let field = match &span {
+                            syn::Member::Named(ident) => ident.clone(),
+                            syn::Member::Unnamed(syn::Index { index, .. }) => {
+                                format_ident!("_{}", index)
+                            }
+                        };
+                        let var = quote! { __miette_internal_var };
+                        if let Some(display) = label {
+                            let (fmt, args) = display.expand_shorthand_cloned(&display_members);
+                            quote! {
+                                miette::macro_helpers::OptionalWrapper::<#ty>::new().to_option(#field)
+                                .map(|#var| miette::LabeledSpan::new_with_span(
+                                    std::option::Option::Some(format!(#fmt #args)),
+                                    #var.clone(),
+                                ))
+                            }
+                        } else {
+                            quote! {
+                                miette::macro_helpers::OptionalWrapper::<#ty>::new().to_option(#field)
+                                .map(|#var| miette::LabeledSpan::new_with_span(
+                                    std::option::Option::None,
+                                    #var.clone(),
+                                ))
+                            }
+                        }
+                    });
+                    let variant_name = ident.clone();
+                    match &fields {
+                        syn::Fields::Unit => None,
+                        _ => Some(quote! {
+                            Self::#variant_name #display_pat => {
+                                use miette::macro_helpers::ToOption;
+                                std::option::Option::Some(std::boxed::Box::new(vec![
+                                    #(#variant_labels),*
+                                ].into_iter().filter(Option::is_some).map(Option::unwrap)))
+                            }
+                        }),
+                    }
+                })
+            },
+        )
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..0f7e64e
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,32 @@
+use quote::quote;
+use syn::{parse_macro_input, DeriveInput};
+
+use diagnostic::Diagnostic;
+
+mod code;
+mod diagnostic;
+mod diagnostic_arg;
+mod diagnostic_source;
+mod fmt;
+mod forward;
+mod help;
+mod label;
+mod related;
+mod severity;
+mod source_code;
+mod url;
+mod utils;
+
+#[proc_macro_derive(
+    Diagnostic,
+    attributes(diagnostic, source_code, label, related, help, diagnostic_source)
+)]
+pub fn derive_diagnostic(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+    let cmd = match Diagnostic::from_derive_input(input) {
+        Ok(cmd) => cmd.gen(),
+        Err(err) => return err.to_compile_error().into(),
+    };
+    // panic!("{:#}", cmd.to_token_stream());
+    quote!(#cmd).into()
+}
diff --git a/src/related.rs b/src/related.rs
new file mode 100644
index 0000000..9b7f9e1
--- /dev/null
+++ b/src/related.rs
@@ -0,0 +1,79 @@
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote};
+use syn::spanned::Spanned;
+
+use crate::{
+    diagnostic::{DiagnosticConcreteArgs, DiagnosticDef},
+    forward::WhichFn,
+    utils::{display_pat_members, gen_all_variants_with},
+};
+
+pub struct Related(syn::Member);
+
+impl Related {
+    pub(crate) fn from_fields(fields: &syn::Fields) -> syn::Result<Option<Self>> {
+        match fields {
+            syn::Fields::Named(named) => Self::from_fields_vec(named.named.iter().collect()),
+            syn::Fields::Unnamed(unnamed) => {
+                Self::from_fields_vec(unnamed.unnamed.iter().collect())
+            }
+            syn::Fields::Unit => Ok(None),
+        }
+    }
+
+    fn from_fields_vec(fields: Vec<&syn::Field>) -> syn::Result<Option<Self>> {
+        for (i, field) in fields.iter().enumerate() {
+            for attr in &field.attrs {
+                if attr.path().is_ident("related") {
+                    let related = if let Some(ident) = field.ident.clone() {
+                        syn::Member::Named(ident)
+                    } else {
+                        syn::Member::Unnamed(syn::Index {
+                            index: i as u32,
+                            span: field.span(),
+                        })
+                    };
+                    return Ok(Some(Related(related)));
+                }
+            }
+        }
+        Ok(None)
+    }
+
+    pub(crate) fn gen_enum(variants: &[DiagnosticDef]) -> Option<TokenStream> {
+        gen_all_variants_with(
+            variants,
+            WhichFn::Related,
+            |ident, fields, DiagnosticConcreteArgs { related, .. }| {
+                let (display_pat, _display_members) = display_pat_members(fields);
+                related.as_ref().map(|related| {
+                    let rel = match &related.0 {
+                        syn::Member::Named(ident) => ident.clone(),
+                        syn::Member::Unnamed(syn::Index { index, .. }) => {
+                            format_ident!("_{}", index)
+                        }
+                    };
+                    quote! {
+                        Self::#ident #display_pat => {
+                            std::option::Option::Some(std::boxed::Box::new(
+                                #rel.iter().map(|x| -> &(dyn miette::Diagnostic) { &*x })
+                            ))
+                        }
+                    }
+                })
+            },
+        )
+    }
+
+    pub(crate) fn gen_struct(&self) -> Option<TokenStream> {
+        let rel = &self.0;
+        Some(quote! {
+            fn related<'a>(&'a self) -> std::option::Option<std::boxed::Box<dyn std::iter::Iterator<Item = &'a dyn miette::Diagnostic> + 'a>> {
+                use ::core::borrow::Borrow;
+                std::option::Option::Some(std::boxed::Box::new(
+                        self.#rel.iter().map(|x| -> &(dyn miette::Diagnostic) { &*x.borrow() })
+                ))
+            }
+        })
+    }
+}
diff --git a/src/severity.rs b/src/severity.rs
new file mode 100644
index 0000000..76126de
--- /dev/null
+++ b/src/severity.rs
@@ -0,0 +1,89 @@
+use proc_macro2::{Span, TokenStream};
+use quote::quote;
+use syn::{
+    parenthesized,
+    parse::{Parse, ParseStream},
+    Token,
+};
+
+use crate::{
+    diagnostic::{DiagnosticConcreteArgs, DiagnosticDef},
+    forward::WhichFn,
+    utils::gen_all_variants_with,
+};
+
+pub struct Severity(pub syn::Ident);
+
+impl Parse for Severity {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let ident = input.parse::<syn::Ident>()?;
+        if ident == "severity" {
+            let la = input.lookahead1();
+            if la.peek(syn::token::Paren) {
+                let content;
+                parenthesized!(content in input);
+                let la = content.lookahead1();
+                if la.peek(syn::LitStr) {
+                    let str = content.parse::<syn::LitStr>()?;
+                    let sev = get_severity(&str.value(), str.span())?;
+                    Ok(Severity(syn::Ident::new(&sev, str.span())))
+                } else {
+                    let ident = content.parse::<syn::Ident>()?;
+                    let sev = get_severity(&ident.to_string(), ident.span())?;
+                    Ok(Severity(syn::Ident::new(&sev, ident.span())))
+                }
+            } else {
+                input.parse::<Token![=]>()?;
+                let str = input.parse::<syn::LitStr>()?;
+                let sev = get_severity(&str.value(), str.span())?;
+                Ok(Severity(syn::Ident::new(&sev, str.span())))
+            }
+        } else {
+            Err(syn::Error::new(
+                ident.span(),
+                "MIETTE BUG: not a severity option",
+            ))
+        }
+    }
+}
+
+fn get_severity(input: &str, span: Span) -> syn::Result<String> {
+    match input.to_lowercase().as_ref() {
+        "error" | "err" => Ok("Error".into()),
+        "warning" | "warn" => Ok("Warning".into()),
+        "advice" | "adv" | "info" => Ok("Advice".into()),
+        _ => Err(syn::Error::new(
+            span,
+            "Invalid severity level. Only Error, Warning, and Advice are supported.",
+        )),
+    }
+}
+
+impl Severity {
+    pub(crate) fn gen_enum(variants: &[DiagnosticDef]) -> Option<TokenStream> {
+        gen_all_variants_with(
+            variants,
+            WhichFn::Severity,
+            |ident, fields, DiagnosticConcreteArgs { severity, .. }| {
+                let severity = &severity.as_ref()?.0;
+                let fields = match fields {
+                    syn::Fields::Named(_) => quote! { { .. } },
+                    syn::Fields::Unnamed(_) => quote! { (..) },
+                    syn::Fields::Unit => quote! {},
+                };
+                Some(
+                    quote! { Self::#ident #fields => std::option::Option::Some(miette::Severity::#severity), },
+                )
+            },
+        )
+    }
+
+    pub(crate) fn gen_struct(&self) -> Option<TokenStream> {
+        let sev = &self.0;
+        Some(quote! {
+            fn severity(&self) -> std::option::Option<miette::Severity> {
+                Some(miette::Severity::#sev)
+            }
+        })
+    }
+}
diff --git a/src/source_code.rs b/src/source_code.rs
new file mode 100644
index 0000000..62f28e7
--- /dev/null
+++ b/src/source_code.rs
@@ -0,0 +1,81 @@
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote};
+use syn::spanned::Spanned;
+
+use crate::{
+    diagnostic::{DiagnosticConcreteArgs, DiagnosticDef},
+    forward::WhichFn,
+    utils::{display_pat_members, gen_all_variants_with},
+};
+
+pub struct SourceCode {
+    source_code: syn::Member,
+}
+
+impl SourceCode {
+    pub fn from_fields(fields: &syn::Fields) -> syn::Result<Option<Self>> {
+        match fields {
+            syn::Fields::Named(named) => Self::from_fields_vec(named.named.iter().collect()),
+            syn::Fields::Unnamed(unnamed) => {
+                Self::from_fields_vec(unnamed.unnamed.iter().collect())
+            }
+            syn::Fields::Unit => Ok(None),
+        }
+    }
+
+    fn from_fields_vec(fields: Vec<&syn::Field>) -> syn::Result<Option<Self>> {
+        for (i, field) in fields.iter().enumerate() {
+            for attr in &field.attrs {
+                if attr.path().is_ident("source_code") {
+                    let source_code = if let Some(ident) = field.ident.clone() {
+                        syn::Member::Named(ident)
+                    } else {
+                        syn::Member::Unnamed(syn::Index {
+                            index: i as u32,
+                            span: field.span(),
+                        })
+                    };
+                    return Ok(Some(SourceCode { source_code }));
+                }
+            }
+        }
+        Ok(None)
+    }
+
+    pub(crate) fn gen_struct(&self, fields: &syn::Fields) -> Option<TokenStream> {
+        let (display_pat, _display_members) = display_pat_members(fields);
+        let src = &self.source_code;
+        Some(quote! {
+            #[allow(unused_variables)]
+            fn source_code(&self) -> std::option::Option<&dyn miette::SourceCode> {
+                let Self #display_pat = self;
+                Some(&self.#src)
+            }
+        })
+    }
+
+    pub(crate) fn gen_enum(variants: &[DiagnosticDef]) -> Option<TokenStream> {
+        gen_all_variants_with(
+            variants,
+            WhichFn::SourceCode,
+            |ident, fields, DiagnosticConcreteArgs { source_code, .. }| {
+                let (display_pat, _display_members) = display_pat_members(fields);
+                source_code.as_ref().and_then(|source_code| {
+                    let field = match &source_code.source_code {
+                        syn::Member::Named(ident) => ident.clone(),
+                        syn::Member::Unnamed(syn::Index { index, .. }) => {
+                            format_ident!("_{}", index)
+                        }
+                    };
+                    let variant_name = ident.clone();
+                    match &fields {
+                        syn::Fields::Unit => None,
+                        _ => Some(quote! {
+                            Self::#variant_name #display_pat => std::option::Option::Some(#field),
+                        }),
+                    }
+                })
+            },
+        )
+    }
+}
diff --git a/src/url.rs b/src/url.rs
new file mode 100644
index 0000000..734d1a4
--- /dev/null
+++ b/src/url.rs
@@ -0,0 +1,139 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{
+    parenthesized,
+    parse::{Parse, ParseStream},
+    Fields, Token,
+};
+
+use crate::{
+    diagnostic::{DiagnosticConcreteArgs, DiagnosticDef},
+    utils::{display_pat_members, gen_all_variants_with, gen_unused_pat},
+};
+use crate::{
+    fmt::{self, Display},
+    forward::WhichFn,
+};
+
+pub enum Url {
+    Display(Display),
+    DocsRs,
+}
+
+impl Parse for Url {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let ident = input.parse::<syn::Ident>()?;
+        if ident == "url" {
+            let la = input.lookahead1();
+            if la.peek(syn::token::Paren) {
+                let content;
+                parenthesized!(content in input);
+                if content.peek(syn::LitStr) {
+                    let fmt = content.parse()?;
+                    let args = if content.is_empty() {
+                        TokenStream::new()
+                    } else {
+                        fmt::parse_token_expr(&content, false)?
+                    };
+                    let display = Display {
+                        fmt,
+                        args,
+                        has_bonus_display: false,
+                    };
+                    Ok(Url::Display(display))
+                } else {
+                    let option = content.parse::<syn::Ident>()?;
+                    if option == "docsrs" {
+                        Ok(Url::DocsRs)
+                    } else {
+                        Err(syn::Error::new(option.span(), "Invalid argument to url() sub-attribute. It must be either a string or a plain `docsrs` identifier"))
+                    }
+                }
+            } else {
+                input.parse::<Token![=]>()?;
+                Ok(Url::Display(Display {
+                    fmt: input.parse()?,
+                    args: TokenStream::new(),
+                    has_bonus_display: false,
+                }))
+            }
+        } else {
+            Err(syn::Error::new(ident.span(), "not a url"))
+        }
+    }
+}
+
+impl Url {
+    pub(crate) fn gen_enum(
+        enum_name: &syn::Ident,
+        variants: &[DiagnosticDef],
+    ) -> Option<TokenStream> {
+        gen_all_variants_with(
+            variants,
+            WhichFn::Url,
+            |ident, fields, DiagnosticConcreteArgs { url, .. }| {
+                let (pat, fmt, args) = match url.as_ref()? {
+                    // fall through to `_ => None` below
+                    Url::Display(display) => {
+                        let (display_pat, display_members) = display_pat_members(fields);
+                        let (fmt, args) = display.expand_shorthand_cloned(&display_members);
+                        (display_pat, fmt.value(), args)
+                    }
+                    Url::DocsRs => {
+                        let pat = gen_unused_pat(fields);
+                        let fmt =
+                            "https://docs.rs/{crate_name}/{crate_version}/{mod_name}/{item_path}"
+                                .into();
+                        let item_path = format!("enum.{}.html#variant.{}", enum_name, ident);
+                        let args = quote! {
+                            ,
+                            crate_name=env!("CARGO_PKG_NAME"),
+                            crate_version=env!("CARGO_PKG_VERSION"),
+                            mod_name=env!("CARGO_PKG_NAME").replace('-', "_"),
+                            item_path=#item_path
+                        };
+                        (pat, fmt, args)
+                    }
+                };
+                Some(quote! {
+                    Self::#ident #pat => std::option::Option::Some(std::boxed::Box::new(format!(#fmt #args))),
+                })
+            },
+        )
+    }
+
+    pub(crate) fn gen_struct(
+        &self,
+        struct_name: &syn::Ident,
+        fields: &Fields,
+    ) -> Option<TokenStream> {
+        let (pat, fmt, args) = match self {
+            Url::Display(display) => {
+                let (display_pat, display_members) = display_pat_members(fields);
+                let (fmt, args) = display.expand_shorthand_cloned(&display_members);
+                (display_pat, fmt.value(), args)
+            }
+            Url::DocsRs => {
+                let pat = gen_unused_pat(fields);
+                let fmt =
+                    "https://docs.rs/{crate_name}/{crate_version}/{mod_name}/{item_path}".into();
+                let item_path = format!("struct.{}.html", struct_name);
+                let args = quote! {
+                    ,
+                    crate_name=env!("CARGO_PKG_NAME"),
+                    crate_version=env!("CARGO_PKG_VERSION"),
+                    mod_name=env!("CARGO_PKG_NAME").replace('-', "_"),
+                    item_path=#item_path
+                };
+                (pat, fmt, args)
+            }
+        };
+        Some(quote! {
+            fn url(&self) -> std::option::Option<std::boxed::Box<dyn std::fmt::Display + '_>> {
+                #[allow(unused_variables, deprecated)]
+                let Self #pat = self;
+                std::option::Option::Some(std::boxed::Box::new(format!(#fmt #args)))
+            }
+        })
+    }
+}
diff --git a/src/utils.rs b/src/utils.rs
new file mode 100644
index 0000000..b867849
--- /dev/null
+++ b/src/utils.rs
@@ -0,0 +1,140 @@
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote, ToTokens};
+use syn::{
+    parse::{Parse, ParseStream},
+    spanned::Spanned,
+};
+
+pub(crate) enum MemberOrString {
+    Member(syn::Member),
+    String(syn::LitStr),
+}
+
+impl ToTokens for MemberOrString {
+    fn to_tokens(&self, tokens: &mut TokenStream) {
+        use MemberOrString::*;
+        match self {
+            Member(member) => member.to_tokens(tokens),
+            String(string) => string.to_tokens(tokens),
+        }
+    }
+}
+
+impl Parse for MemberOrString {
+    fn parse(input: ParseStream) -> syn::Result<Self> {
+        let lookahead = input.lookahead1();
+        if lookahead.peek(syn::Ident) || lookahead.peek(syn::LitInt) {
+            Ok(MemberOrString::Member(input.parse()?))
+        } else if lookahead.peek(syn::LitStr) {
+            Ok(MemberOrString::String(input.parse()?))
+        } else {
+            Err(syn::Error::new(
+                input.span(),
+                "Expected a string or a field reference.",
+            ))
+        }
+    }
+}
+
+use crate::{
+    diagnostic::{DiagnosticConcreteArgs, DiagnosticDef},
+    forward::WhichFn,
+};
+
+pub(crate) fn gen_all_variants_with(
+    variants: &[DiagnosticDef],
+    which_fn: WhichFn,
+    mut f: impl FnMut(&syn::Ident, &syn::Fields, &DiagnosticConcreteArgs) -> Option<TokenStream>,
+) -> Option<TokenStream> {
+    let pairs = variants
+        .iter()
+        .filter_map(|def| {
+            def.args
+                .forward_or_override_enum(&def.ident, which_fn, |concrete| {
+                    f(&def.ident, &def.fields, concrete)
+                })
+        })
+        .collect::<Vec<_>>();
+    if pairs.is_empty() {
+        return None;
+    }
+    let signature = which_fn.signature();
+    let catchall = which_fn.catchall_arm();
+    Some(quote! {
+        #signature {
+            #[allow(unused_variables, deprecated)]
+            match self {
+                #(#pairs)*
+                #catchall
+            }
+        }
+    })
+}
+
+use crate::fmt::Display;
+use std::collections::HashSet;
+
+pub(crate) fn gen_unused_pat(fields: &syn::Fields) -> TokenStream {
+    match fields {
+        syn::Fields::Named(_) => quote! { { .. } },
+        syn::Fields::Unnamed(_) => quote! { ( .. ) },
+        syn::Fields::Unit => quote! {},
+    }
+}
+
+/// Goes in the slot `let Self #pat = self;` or `match self { Self #pat => ...
+/// }`.
+fn gen_fields_pat(fields: &syn::Fields) -> TokenStream {
+    let member_idents = fields.iter().enumerate().map(|(i, field)| {
+        field
+            .ident
+            .as_ref()
+            .cloned()
+            .unwrap_or_else(|| format_ident!("_{}", i))
+    });
+    match fields {
+        syn::Fields::Named(_) => quote! {
+            { #(#member_idents),* }
+        },
+        syn::Fields::Unnamed(_) => quote! {
+            ( #(#member_idents),* )
+        },
+        syn::Fields::Unit => quote! {},
+    }
+}
+
+/// The returned tokens go in the slot `let Self #pat = self;` or `match self {
+/// Self #pat => ... }`. The members can be passed to
+/// `Display::expand_shorthand[_cloned]`.
+pub(crate) fn display_pat_members(fields: &syn::Fields) -> (TokenStream, HashSet<syn::Member>) {
+    let pat = gen_fields_pat(fields);
+    let members: HashSet<syn::Member> = fields
+        .iter()
+        .enumerate()
+        .map(|(i, field)| {
+            if let Some(ident) = field.ident.as_ref().cloned() {
+                syn::Member::Named(ident)
+            } else {
+                syn::Member::Unnamed(syn::Index {
+                    index: i as u32,
+                    span: field.span(),
+                })
+            }
+        })
+        .collect();
+    (pat, members)
+}
+
+impl Display {
+    /// Returns `(fmt, args)` which must be passed to some kind of format macro
+    /// without tokens in between, i.e. `format!(#fmt #args)`.
+    pub(crate) fn expand_shorthand_cloned(
+        &self,
+        members: &HashSet<syn::Member>,
+    ) -> (syn::LitStr, TokenStream) {
+        let mut display = self.clone();
+        display.expand_shorthand(members);
+        let Display { fmt, args, .. } = display;
+        (fmt, args)
+    }
+}
author	Matthew Maurer <mmaurer@google.com>	2023-06-26 23:37:40 +0000
committer	Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>	2023-06-26 23:37:40 +0000
commit	cf18a0d3a3b53ce574de2906a5f82f89a77f1888 (patch)
tree	c82295365488871209366131d0b6d3708991d841
parent	5d5fc11f1e70fa2ef447cf14a8f6f5acae51d2b4 (diff)
parent	b980cfea52a3e39940ec28c531f7e1d230f8c28a (diff)
download	miette-derive-cf18a0d3a3b53ce574de2906a5f82f89a77f1888.tar.gz