1 files changed, 74 insertions, 0 deletions
diff --git a/resolve/binding.go b/resolve/binding.go
new file mode 100644
index 0000000..6b99f4b
--- /dev/null
+++ b/resolve/binding.go
@@ -0,0 +1,74 @@
+// Copyright 2019 The Bazel Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package resolve
+
+import "go.starlark.net/syntax"
+
+// This file defines resolver data types saved in the syntax tree.
+// We cannot guarantee API stability for these types
+// as they are closely tied to the implementation.
+
+// A Binding contains resolver information about an identifer.
+// The resolver populates the Binding field of each syntax.Identifier.
+// The Binding ties together all identifiers that denote the same variable.
+type Binding struct {
+	Scope Scope
+
+	// Index records the index into the enclosing
+	// - {DefStmt,File}.Locals, if Scope==Local
+	// - DefStmt.FreeVars,      if Scope==Free
+	// - File.Globals,          if Scope==Global.
+	// It is zero if Scope is Predeclared, Universal, or Undefined.
+	Index int
+
+	First *syntax.Ident // first binding use (iff Scope==Local/Free/Global)
+}
+
+// The Scope of Binding indicates what kind of scope it has.
+type Scope uint8
+
+const (
+	Undefined   Scope = iota // name is not defined
+	Local                    // name is local to its function or file
+	Cell                     // name is function-local but shared with a nested function
+	Free                     // name is cell of some enclosing function
+	Global                   // name is global to module
+	Predeclared              // name is predeclared for this module (e.g. glob)
+	Universal                // name is universal (e.g. len)
+)
+
+var scopeNames = [...]string{
+	Undefined:   "undefined",
+	Local:       "local",
+	Cell:        "cell",
+	Free:        "free",
+	Global:      "global",
+	Predeclared: "predeclared",
+	Universal:   "universal",
+}
+
+func (scope Scope) String() string { return scopeNames[scope] }
+
+// A Module contains resolver information about a file.
+// The resolver populates the Module field of each syntax.File.
+type Module struct {
+	Locals  []*Binding // the file's (comprehension-)local variables
+	Globals []*Binding // the file's global variables
+}
+
+// A Function contains resolver information about a named or anonymous function.
+// The resolver populates the Function field of each syntax.DefStmt and syntax.LambdaExpr.
+type Function struct {
+	Pos    syntax.Position // of DEF or LAMBDA
+	Name   string          // name of def, or "lambda"
+	Params []syntax.Expr   // param = ident | ident=expr | * | *ident | **ident
+	Body   []syntax.Stmt   // contains synthetic 'return expr' for lambda
+
+	HasVarargs      bool       // whether params includes *args (convenience)
+	HasKwargs       bool       // whether params includes **kwargs (convenience)
+	NumKwonlyParams int        // number of keyword-only optional parameters
+	Locals          []*Binding // this function's local/cell variables, parameters first
+	FreeVars        []*Binding // enclosing cells to capture in closure
+}