go/types, types2: better error message for blank interface method nam…

…e (cleanup)

Use the 1.17 compiler error message.

Change-Id: Ic62de5bfc9681674069934afc590f5840729f8e2
Reviewed-on: https://go-review.googlesource.com/c/go/+/396297
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

src/cmd/compile/internal/types2/interface.go

@@ -132,11 +132,7 @@ func (check *Checker) interfaceType(ityp *Interface, iface *syntax.InterfaceType
 		// We have a method with name f.Name.
 		name := f.Name.Value
 		if name == "_" {
-			if check.conf.CompilerErrorMessages {
-				check.error(f.Name, "methods must have a unique non-blank name")
-			} else {
-				check.error(f.Name, "invalid method name _")
-			}
+			check.error(f.Name, "methods must have a unique non-blank name")
 			continue // ignore
 		}
 

src/cmd/compile/internal/types2/testdata/check/decls0.go

@@ -194,8 +194,8 @@ func (S0) m4() (x *S0 /* ERROR illegal cycle in method declaration */ .m4) { ret
 
 // interfaces may not have any blank methods
 type BlankI interface {
-	_ /* ERROR "invalid method name" */ ()
-	_ /* ERROR "invalid method name" */ (float32) int
+	_ /* ERROR "methods must have a unique non-blank name" */ ()
+	_ /* ERROR "methods must have a unique non-blank name" */ (float32) int
 	m()
 }
 

src/go/types/interface.go

@@ -173,7 +173,7 @@ func (check *Checker) interfaceType(ityp *Interface, iface *ast.InterfaceType, d
 		// We have a method with name f.Names[0].
 		name := f.Names[0]
 		if name.Name == "_" {
-			check.errorf(name, _BlankIfaceMethod, "invalid method name _")
+			check.errorf(name, _BlankIfaceMethod, "methods must have a unique non-blank name")
 			continue // ignore
 		}
 

src/go/types/testdata/check/decls0.go

@@ -196,8 +196,8 @@ func (S0) m4 () (x *S0 /* ERROR illegal cycle in method declaration */ .m4) { re
 
 // interfaces may not have any blank methods
 type BlankI interface {
-	_ /* ERROR "invalid method name" */ ()
-	_ /* ERROR "invalid method name" */ (float32) int
+	_ /* ERROR "methods must have a unique non-blank name" */ ()
+	_ /* ERROR "methods must have a unique non-blank name" */ (float32) int
 	m()
 }