cmd/gc: fix escape analysis for &x inside switch x := v.(type)

The analysis for &x was using the loop depth on x set
during x's declaration. A type switch creates a list of
implicit declarations that were not getting initialized
with loop depths.

Fixes issue 8176.

LGTM=iant
R=iant
CC=golang-codereviews
https://codereview.appspot.com/108860043

1 files changed, 10 insertions, 0 deletions

diff --git a/test/escape2.go b/test/escape2.go
index 8cb3b6df6..f00741dc2 100644
--- a/test/escape2.go
+++ b/test/escape2.go
@@ -1468,3 +1468,13 @@ func foo152() {
 	v := NewV(u)
 	println(v)
 }
+
+// issue 8176 - &x in type switch body not marked as escaping
+
+func foo153(v interface{}) *int { // ERROR "leaking param: v"
+	switch x := v.(type) {
+	case int: // ERROR "moved to heap: x"
+		return &x // ERROR "&x escapes to heap"
+	}
+	panic(0)
+}