cmd/compile: allow conversion from slice to array ptr

Panic if the slice is too short.

Updates #395

Change-Id: I90f4bff2da5d8f3148ba06d2482084f32b25c29a
Reviewed-on: https://go-review.googlesource.com/c/go/+/301650
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/types2/conversions.go b/src/cmd/compile/internal/types2/conversions.go
index eabed7ba9b..51be50e9ad 100644
--- a/src/cmd/compile/internal/types2/conversions.go
+++ b/src/cmd/compile/internal/types2/conversions.go
@@ -135,6 +135,18 @@ func (x *operand) convertibleTo(check *Checker, T Type) bool {
 		return true
 	}
 
+	// "x is a slice, T is a pointer-to-array type,
+	// and the slice and array types have identical element types."
+	if s := asSlice(V); s != nil {
+		if p := asPointer(T); p != nil {
+			if a := asArray(p.Elem()); a != nil {
+				if check.identical(s.Elem(), a.Elem()) {
+					return true
+				}
+			}
+		}
+	}
+
 	return false
 }