cmd/compile/internal/syntax: better error message for erroneous method declaration

Also make error recovery slightly more robust in this case.

Fixes #56022.

Change-Id: I1c01c1465adb48c71367d037b6f0e3fe56f68ec9
Reviewed-on: https://go-review.googlesource.com/c/go/+/438540
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

1 files changed, 11 insertions, 11 deletions

diff --git a/src/cmd/compile/internal/syntax/parser.go b/src/cmd/compile/internal/syntax/parser.go
index b31b712f1d..d80b269557 100644
--- a/src/cmd/compile/internal/syntax/parser.go
+++ b/src/cmd/compile/internal/syntax/parser.go
@@ -767,7 +767,9 @@ func (p *parser) funcDeclOrNil() *FuncDecl {
 	f.pos = p.pos()
 	f.Pragma = p.takePragma()
 
+	var context string
 	if p.got(_Lparen) {
+		context = "method"
 		rcvr := p.paramList(nil, nil, _Rparen, false)
 		switch len(rcvr) {
 		case 0:
@@ -780,19 +782,17 @@ func (p *parser) funcDeclOrNil() *FuncDecl {
 		}
 	}
 
-	if p.tok != _Name {
-		p.syntaxError("expected name or (")
+	if p.tok == _Name {
+		f.Name = p.name()
+		f.TParamList, f.Type = p.funcType(context)
+	} else {
+		msg := "expected name or ("
+		if context != "" {
+			msg = "expected name"
+		}
+		p.syntaxError(msg)
 		p.advance(_Lbrace, _Semi)
-		return nil
-	}
-
-	f.Name = p.name()
-
-	context := ""
-	if f.Recv != nil {
-		context = "method" // don't permit (method) type parameters in funcType
 	}
-	f.TParamList, f.Type = p.funcType(context)
 
 	if p.tok == _Lbrace {
 		f.Body = p.funcBody()