cmd/compile: handle copy in escape analysis

Somehow we missed this!
Fixes #11387.

Change-Id: Ida08fe52eff7da2ef7765b4cf35a39a301420c43
Reviewed-on: https://go-review.googlesource.com/11460
Reviewed-by: David Chase <drchase@google.com>

src/cmd/compile/internal/gc/esc.go

@@ -809,6 +809,9 @@ func esc(e *EscState, n *Node, up *Node) {
 		}
 		escassignDereference(e, &e.theSink, n.List.N) // The original elements are now leaked, too
 
+	case OCOPY:
+		escassignDereference(e, &e.theSink, n.Right) // lose track of assign of dereference
+
 	case OCONV, OCONVNOP:
 		escassign(e, n, n.Left)
 

test/escape2.go

@@ -858,8 +858,8 @@ func foo103(m [1]*int, x *int) { // ERROR "foo103 m does not escape$" "foo103 x
 
 var y []*int
 
-// does not leak x
-func foo104(x []*int) { // ERROR "foo104 x does not escape$"
+// does not leak x but does leak content
+func foo104(x []*int) { // ERROR "leaking param content: x"
 	copy(y, x)
 }
 
@@ -1820,3 +1820,11 @@ func issue10353b() {
 	}
 	_ = f
 }
+
+func issue11387(x int) func() int {
+	f := func() int { return x }    // ERROR "func literal escapes to heap"
+	slice1 := []func() int{f}       // ERROR "\[\].* does not escape"
+	slice2 := make([]func() int, 1) // ERROR "make\(.*\) does not escape"
+	copy(slice2, slice1)
+	return slice2[0]
+}

test/escape2n.go

@@ -858,8 +858,8 @@ func foo103(m [1]*int, x *int) { // ERROR "foo103 m does not escape$" "foo103 x
 
 var y []*int
 
-// does not leak x
-func foo104(x []*int) { // ERROR "foo104 x does not escape$"
+// does not leak x but does leak content
+func foo104(x []*int) { // ERROR "leaking param content: x"
 	copy(y, x)
 }
 
@@ -1820,3 +1820,11 @@ func issue10353b() {
 	}
 	_ = f
 }
+
+func issue11387(x int) func() int {
+	f := func() int { return x }    // ERROR "func literal escapes to heap"
+	slice1 := []func() int{f}       // ERROR "\[\].* does not escape"
+	slice2 := make([]func() int, 1) // ERROR "make\(.*\) does not escape"
+	copy(slice2, slice1)
+	return slice2[0]
+}