From 5726af54eb3a52b9446a834991110b945e780e99 Mon Sep 17 00:00:00 2001
From: Daniel Morsing <daniel.morsing@gmail.com>
Date: Wed, 29 Apr 2015 10:51:42 +0100
Subject: [PATCH] cmd/internal/gc: ignore declarations of types for goto
 validation

Fixes #8042.

Change-Id: I75080f24104256065fd73b07a13c5b8e7d6da94c
Reviewed-on: https://go-review.googlesource.com/9442
Reviewed-by: Russ Cox <rsc@golang.org>
---
 src/cmd/internal/gc/dcl.go |  3 +++
 src/cmd/internal/gc/gen.go | 21 ++++++++++++++++++---
 src/cmd/internal/gc/go.go  |  1 +
 test/goto.go               | 16 ++++++++++++++++
 4 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/src/cmd/internal/gc/dcl.go b/src/cmd/internal/gc/dcl.go
index 85a33bec3f..58b69ab8f9 100644
--- a/src/cmd/internal/gc/dcl.go
+++ b/src/cmd/internal/gc/dcl.go
@@ -65,6 +65,9 @@ func popdcl() {
 		}
 		s = Pkglookup(d.Name, d.Pkg)
 		lno = int(s.Lastlineno)
+		if s.Def != nil {
+			d.whyPushed = s.Def.Op
+		}
 		dcopy(s, d)
 		d.Lastlineno = int32(lno)
 		if dflag() {
diff --git a/src/cmd/internal/gc/gen.go b/src/cmd/internal/gc/gen.go
index cd0e650ca9..bba04d41ad 100644
--- a/src/cmd/internal/gc/gen.go
+++ b/src/cmd/internal/gc/gen.go
@@ -159,6 +159,21 @@ func checkgoto(from *Node, to *Node) {
 		fs = fs.Link
 	}
 	if fs != to.Sym {
+		// more declarations at label than at goto.
+		// figure out if they are all types.
+		ts := to.Sym
+		ntt := nt
+		for ; ntt > nf; ntt-- {
+			if ts.whyPushed != OTYPE {
+				break
+			}
+			ts = ts.Link
+		}
+		// all types, nothing to see here.
+		if ntt == nf {
+			return
+		}
+
 		lno := int(lineno)
 		setlineno(from)
 
@@ -168,11 +183,11 @@ func checkgoto(from *Node, to *Node) {
 		var block *Sym
 
 		var dcl *Sym
-		ts := to.Sym
+		ts = to.Sym
 		for ; nt > nf; nt-- {
 			if ts.Pkg == nil {
 				block = ts
-			} else {
+			} else if ts.whyPushed != OTYPE {
 				dcl = ts
 			}
 			ts = ts.Link
@@ -181,7 +196,7 @@ func checkgoto(from *Node, to *Node) {
 		for ts != fs {
 			if ts.Pkg == nil {
 				block = ts
-			} else {
+			} else if ts.whyPushed != OTYPE {
 				dcl = ts
 			}
 			ts = ts.Link
diff --git a/src/cmd/internal/gc/go.go b/src/cmd/internal/gc/go.go
index 31692bdf00..4800218c95 100644
--- a/src/cmd/internal/gc/go.go
+++ b/src/cmd/internal/gc/go.go
@@ -111,6 +111,7 @@ type Sym struct {
 	Uniqgen   uint32
 	Importdef *Pkg   // where imported definition was found
 	Linkname  string // link name
+	whyPushed uint8  // why this symbol pushed onto dclstack. Same as Node.Op. Used by goto validation
 
 	// saved and restored by dcopy
 	Pkg        *Pkg
diff --git a/test/goto.go b/test/goto.go
index ca477b3d0c..c626f3d1c1 100644
--- a/test/goto.go
+++ b/test/goto.go
@@ -536,3 +536,19 @@ func _() {
 		goto L // ERROR "goto L jumps into block starting at LINE-4|goto jumps into block"
 	}
 }
+
+// issue 8042
+func _() {
+	goto L
+	type a int
+	L:
+}
+
+// make sure we only complain about variable declarations.
+func _() {
+	goto L // ERROR "goto L jumps over declaration of x at LINE+2|goto jumps over declaration"
+	type a int
+	x := 1	// GCCGO_ERROR "defined here"
+	_ = x
+L:
+}
-- 
2.48.1