go/types: fix errors in recording type information

In my previous change, I didn't use the correct functions for continuing
to record type informations after errors. Change to using the correct
functions, and add a comment to clarify in expr.go.

Updates #22467

Change-Id: I66ebb636ceb2b994db652343430f0551db0050c3
Reviewed-on: https://go-review.googlesource.com/128835
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/go/types/api_test.go

@@ -42,7 +42,7 @@ func mustTypecheck(t *testing.T, path, source string, info *Info) string {
 	return pkg.Name()
 }
 
-func maybeTypecheck(t *testing.T, path, source string, info *Info) string {
+func mayTypecheck(t *testing.T, path, source string, info *Info) string {
 	fset := token.NewFileSet()
 	f, err := parser.ParseFile(fset, path, source, 0)
 	if f == nil { // ignore errors unless f is nil
@@ -265,7 +265,7 @@ func TestTypesInfo(t *testing.T) {
 
 	for _, test := range tests {
 		info := Info{Types: make(map[ast.Expr]TypeAndValue)}
-		name := maybeTypecheck(t, "TypesInfo", test.src, &info)
+		name := mayTypecheck(t, "TypesInfo", test.src, &info)
 
 		// look for expression type
 		var typ Type

src/go/types/assignments.go

@@ -310,7 +310,7 @@ func (check *Checker) shortVarDecl(pos token.Pos, lhs, rhs []ast.Expr) {
 				check.recordDef(ident, obj)
 			}
 		} else {
-			check.expr(&operand{}, lhs)
+			check.useLHS(lhs)
 			check.errorf(lhs.Pos(), "cannot declare %s", lhs)
 		}
 		if obj == nil {

src/go/types/call.go

@@ -34,9 +34,7 @@ func (check *Checker) call(x *operand, e *ast.CallExpr) exprKind {
 				check.conversion(x, T)
 			}
 		default:
-			for _, arg := range e.Args {
-				check.expr(&operand{}, arg)
-			}
+			check.use(e.Args...)
 			check.errorf(e.Args[n-1].Pos(), "too many arguments in conversion to %s", T)
 		}
 		x.expr = e

src/go/types/expr.go

@@ -1094,6 +1094,8 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
 						continue
 					}
 					key, _ := kv.Key.(*ast.Ident)
+					// do all possible checks early (before exiting due to errors)
+					// so we don't drop information on the floor
 					check.expr(x, kv.Value)
 					if key == nil {
 						check.errorf(kv.Pos(), "invalid field name %s in struct literal", kv.Key)