cmd/gc: fix comparison of struct with _ field

Fixes #2989.

R=ken2
CC=golang-dev
https://golang.org/cl/5674091

1 files changed, 19 insertions, 0 deletions

diff --git a/test/cmp.go b/test/cmp.go
index 795245f2f5..a9d0375b24 100644
--- a/test/cmp.go
+++ b/test/cmp.go
@@ -281,6 +281,25 @@ func main() {
 		isfalse(ix != z)
 		isfalse(iz != x)
 	}
+	
+	// structs with _ fields
+	{
+		var x = struct {
+			x int
+			_ []int
+			y float64
+			_ float64
+			z int
+		}{
+			x: 1, y: 2, z: 3,
+		}
+		var ix interface{} = x
+		
+		istrue(x == x)
+		istrue(x == ix)
+		istrue(ix == x)
+		istrue(ix == ix)
+	}
 
 	// arrays
 	{