cmd/gc: for loop init statement misanalyzed by escape analysis

Logically, the init statement is in the enclosing scopes loopdepth, not inside the for loop.

Fixes #7313.

LGTM=rsc
R=golang-codereviews, gobot, rsc
CC=golang-codereviews
https://golang.org/cl/62430043

1 files changed, 32 insertions, 0 deletions

diff --git a/test/escape2.go b/test/escape2.go
index be89c2d840..73342fd2bc 100644
--- a/test/escape2.go
+++ b/test/escape2.go
@@ -1357,3 +1357,35 @@ func foo144() {
 //go:noescape
 
 func foo144b(*int)
+
+// issue 7313: for loop init should not be treated as "in loop"
+
+type List struct {
+	Next *List
+}
+
+func foo145(l List) { // ERROR "l does not escape"
+	var p *List
+	for p = &l; p.Next != nil; p = p.Next { // ERROR "&l does not escape"
+	}
+}
+
+func foo146(l List) { // ERROR "l does not escape"
+	var p *List
+	p = &l // ERROR "&l does not escape"
+	for ; p.Next != nil; p = p.Next {
+	}
+}
+
+func foo147(l List) { // ERROR "l does not escape"
+	var p *List
+	p = &l // ERROR "&l does not escape"
+	for p.Next != nil {
+		p = p.Next
+	}
+}
+
+func foo148(l List) { // ERROR " l does not escape"
+	for p := &l; p.Next != nil; p = p.Next { // ERROR "&l does not escape"
+	}
+}