cmd/gc: accept switches on comparable arrays.

The compiler is incorrectly rejecting switches on arrays of
comparable types. It also doesn't catch incomparable structs
when typechecking the switch, leading to unreadable errors
during typechecking of the generated code.

Fixes #3894.

R=rsc
CC=gobot, golang-dev, r, remy
https://golang.org/cl/6442074

1 files changed, 11 insertions, 0 deletions

diff --git a/test/switch3.go b/test/switch3.go
index dcb6fff208..28705e464e 100644
--- a/test/switch3.go
+++ b/test/switch3.go
@@ -45,6 +45,17 @@ func bad() {
 	case f1: // ERROR "can only compare func f to nil|func can only be compared to nil"
 	default:
 	}
+
+	var ar, ar1 [4]func()
+	switch ar { // ERROR "cannot switch on"
+	case ar1:
+	default:
+	}
+
+	var st, st1 struct{ f func() }
+	switch st { // ERROR "cannot switch on"
+	case st1:
+	}
 }
 
 func good() {