From bdc4ffe9a86d1dae0fef9de8395850e5c0b391c6 Mon Sep 17 00:00:00 2001
From: Robert Griesemer <gri@golang.org>
Date: Tue, 1 Dec 2020 12:18:20 -0800
Subject: [PATCH] [dev.typeparams] cmd/compile/internal/types2: add
 Config.IgnoreBranches flag

If the new Config.IgnoreBranches flag is set, the typechecker
ignores errors due to misplaced labels, break, continue,
fallthrough, or goto statements.

Since the syntax parser already checks these errors, we need
to disable a 2nd check by the typechecker to avoid duplicate
errors when running the compiler with the new typechecker.

Adjusted test/run.go to not ignore some of the tests that
used to fail because of duplicate errors.

Change-Id: I8756eb1d44f67afef5e57da289cd604b8e1716db
Reviewed-on: https://go-review.googlesource.com/c/go/+/274612
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
---
 src/cmd/compile/internal/gc/noder.go    |  3 ++-
 src/cmd/compile/internal/types2/api.go  |  5 +++++
 src/cmd/compile/internal/types2/stmt.go | 10 +++++++++-
 test/run.go                             |  4 +---
 4 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/cmd/compile/internal/gc/noder.go b/src/cmd/compile/internal/gc/noder.go
index 1cdb6bc08c..5115932b1e 100644
--- a/src/cmd/compile/internal/gc/noder.go
+++ b/src/cmd/compile/internal/gc/noder.go
@@ -84,7 +84,8 @@ func parseFiles(filenames []string, allowGenerics bool) (lines uint) {
 
 		conf := types2.Config{
 			InferFromConstraints:  true,
-			CompilerErrorMessages: true,
+			IgnoreBranches:        true, // parser already checked via syntax.CheckBranches mode
+			CompilerErrorMessages: true, // use error strings matching existing compiler errors
 			Error: func(err error) {
 				terr := err.(types2.Error)
 				if len(terr.Msg) > 0 && terr.Msg[0] == '\t' {
diff --git a/src/cmd/compile/internal/types2/api.go b/src/cmd/compile/internal/types2/api.go
index a40665ee17..c5c30babff 100644
--- a/src/cmd/compile/internal/types2/api.go
+++ b/src/cmd/compile/internal/types2/api.go
@@ -119,6 +119,11 @@ type Config struct {
 	//          Do not use casually!
 	FakeImportC bool
 
+	// If IgnoreBranches is set, errors related to incorrectly placed
+	// labels, gotos, break, continue, and fallthrough statements are
+	// ignored.
+	IgnoreBranches bool
+
 	// If CompilerErrorMessages is set, errors are reported using
 	// cmd/compile error strings to match $GOROOT/test errors.
 	// TODO(gri) Consolidate error messages and remove this flag.
diff --git a/src/cmd/compile/internal/types2/stmt.go b/src/cmd/compile/internal/types2/stmt.go
index 37aa3c7308..11a9b8313f 100644
--- a/src/cmd/compile/internal/types2/stmt.go
+++ b/src/cmd/compile/internal/types2/stmt.go
@@ -42,6 +42,7 @@ func (check *Checker) funcBody(decl *declInfo, name string, sig *Signature, body
 	check.stmtList(0, body.List)
 
 	if check.hasLabel {
+		assert(!check.conf.IgnoreBranches)
 		check.labels(body)
 	}
 
@@ -316,7 +317,7 @@ func (check *Checker) stmt(ctxt stmtContext, s syntax.Stmt) {
 		check.declStmt(s.DeclList)
 
 	case *syntax.LabeledStmt:
-		check.hasLabel = true
+		check.hasLabel = !check.conf.IgnoreBranches
 		check.stmt(ctxt, s.Stmt)
 
 	case *syntax.ExprStmt:
@@ -443,6 +444,10 @@ func (check *Checker) stmt(ctxt stmtContext, s syntax.Stmt) {
 		}
 
 	case *syntax.BranchStmt:
+		if check.conf.IgnoreBranches {
+			break
+		}
+
 		if s.Label != nil {
 			check.hasLabel = true
 			return // checked in 2nd pass (check.labels)
@@ -464,6 +469,9 @@ func (check *Checker) stmt(ctxt stmtContext, s syntax.Stmt) {
 				}
 				check.error(s, msg)
 			}
+		case syntax.Goto:
+			// goto's must have labels, should have been caught above
+			fallthrough
 		default:
 			check.invalidASTf(s, "branch statement: %s", s.Tok)
 		}
diff --git a/test/run.go b/test/run.go
index 319aed5ac1..1eef6f1f35 100644
--- a/test/run.go
+++ b/test/run.go
@@ -771,15 +771,12 @@ func (t *test) run() {
 			"func1.go",
 			"funcdup.go",
 			"funcdup2.go",
-			"goto.go",
 			"import1.go",
 			"import5.go",
 			"import6.go",
 			"init.go",
 			"initializerr.go",
 			"initloop.go",
-			"label.go",
-			"label1.go",
 			"makechan.go",
 			"makemap.go",
 			"makenew.go",
@@ -792,6 +789,7 @@ func (t *test) run() {
 			"shift1.go",
 			"slice3err.go",
 			"switch3.go",
+			"switch4.go",
 			"switch5.go",
 			"switch6.go",
 			"switch7.go",
-- 
2.48.1