test: lock in test for _ assignment evaluation/zerodivide panic

Fixes #5790.
Fixes #18421.

* Lock in _ = x1/x2 divide by zero runtime panics since
it is actually evaluated and not discarded as in previous
versions before Go1.8.
* Update a test that was skipping over zerodivide tests
that expected runtime panics, enabling us to check for
the expected panics.

Change-Id: I0af0a6ecc19345fa9763ab2e35b275fb2d9d0194
Reviewed-on: https://go-review.googlesource.com/34712
Reviewed-by: Keith Randall <khr@golang.org>

diff --git a/test/zerodivide.go b/test/zerodivide.go
index 9ab2713535906194bc917ad50f76f4d062bc56ef..214d481164442aab25c7e5f9189933108a54c005 100644 (file)
--- a/test/zerodivide.go
+++ b/test/zerodivide.go
@@ -28,6 +28,8 @@ var (
        i32, j32, k32 int32 = 0, 0, 1
        i64, j64, k64 int64 = 0, 0, 1
 
+       bb = []int16{2, 0}
+
        u, v, w       uint    = 0, 0, 1
        u8, v8, w8    uint8   = 0, 0, 1
        u16, v16, w16 uint16  = 0, 0, 1
@@ -124,6 +126,10 @@ var errorTests = []ErrorTest{
        ErrorTest{"int32 1/0", func() { use(k32 / j32) }, "divide"},
        ErrorTest{"int64 1/0", func() { use(k64 / j64) }, "divide"},
 
+       // From issue 5790, we should ensure that _ assignments
+       // still evaluate and generate zerodivide panics.
+       ErrorTest{"int16 _ = bb[0]/bb[1]", func() { _ = bb[0] / bb[1] }, "divide"},
+
        ErrorTest{"uint 0/0", func() { use(u / v) }, "divide"},
        ErrorTest{"uint8 0/0", func() { use(u8 / v8) }, "divide"},
        ErrorTest{"uint16 0/0", func() { use(u16 / v16) }, "divide"},
@@ -195,9 +201,6 @@ func alike(a, b float64) bool {
 func main() {
        bad := false
        for _, t := range errorTests {
-               if t.err != "" {
-                       continue
-               }
                err := error_(t.fn)
                switch {
                case t.err == "" && err == "":