internal/lsp: add type error fixes to existing diagnostics

This change is the first step in handling golang/go#38136. Instead of
creating multiple diagnostic reports for type error analyzers, we add
suggested fixes to the existing reports. To match the analyzers for
FindAnalysisError, we add an ErrorMatch function to source.Analyzer.

This is not an ideal solution, but it was the best one I could come up
with without modifying the go/analysis API. analysisinternal could be
used for this purpose, but it seemed to complicated to be worth it, and
this is fairly simple. I think that go/analysis itself might need to be
extended for type error analyzers, but these temporary measures will
help us understand the kinds of features we need for type error
analyzers.

A follow-up CL might be to not add reports for type error analyzers
until the end of source.Diagnostic, which would remove the need for the
look-up.

Fixes golang/go#38136

Change-Id: I25bc6396b09d49facecd918bf5591d2d5bdf1b3a
Reviewed-on: https://go-review.googlesource.com/c/tools/+/226777
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/internal/lsp/analysis/noresultvalues/noresultvalues.go b/internal/lsp/analysis/noresultvalues/noresultvalues.go
index 0259691ed..0e6b26f8b 100644
--- a/internal/lsp/analysis/noresultvalues/noresultvalues.go
+++ b/internal/lsp/analysis/noresultvalues/noresultvalues.go
@@ -34,8 +34,6 @@ var Analyzer = &analysis.Analyzer{
 	RunDespiteErrors: true,
 }
 
-const noResultValuesMsg = "no result values expected"
-
 func run(pass *analysis.Pass) (interface{}, error) {
 	inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
 	errors := analysisinternal.GetTypeErrors(pass)
@@ -56,7 +54,7 @@ func run(pass *analysis.Pass) (interface{}, error) {
 		}
 
 		for _, err := range errors {
-			if err.Msg != noResultValuesMsg {
+			if !FixesError(err.Msg) {
 				continue
 			}
 			if retStmt.Pos() >= err.Pos || err.Pos >= retStmt.End() {
@@ -83,3 +81,7 @@ func run(pass *analysis.Pass) (interface{}, error) {
 	})
 	return nil, nil
 }
+
+func FixesError(msg string) bool {
+	return msg == "no result values expected"
+}