test: add tests for escape analysis of interface conversions

The false positives (var incorrectly escapes) are marked with BAD.

Change-Id: If64fabb6ea96de44a1177d9ab12e2ccc579fe0c4
Reviewed-on: https://go-review.googlesource.com/5294
Reviewed-by: Keith Randall <khr@golang.org>
diff --git a/test/escape_map.go b/test/escape_map.go
index 53fcfdf..868c456 100644
--- a/test/escape_map.go
+++ b/test/escape_map.go
@@ -95,7 +95,7 @@
 	i := 0                     // ERROR "moved to heap: i"
 	j := 0                     // ERROR "moved to heap: j"
 	m := map[*int]*int{&i: &j} // ERROR "&i escapes to heap" "&j escapes to heap" "literal escapes to heap"
-	sink = m
+	sink = m // ERROR "m escapes to heap"
 }
 
 func map9() *int {