AstGen: fix if, orelse, catch, with unreachable bodies

Before, the system to replace a result location pointer with a
traditional break instruction did not notice the case when one of the
bodies was unreachable. Now, the emitted ZIR code is improved and
simplified in this case, resulting in a new passing behavior test.

1 files changed, 8 insertions, 0 deletions

diff --git a/test/behavior/if.zig b/test/behavior/if.zig
index 191d4817df..a1f722d827 100644
--- a/test/behavior/if.zig
+++ b/test/behavior/if.zig
@@ -65,3 +65,11 @@ test "labeled break inside comptime if inside runtime if" {
     }
     try expect(answer == 42);
 }
+
+test "const result loc, runtime if cond, else unreachable" {
+    const Num = enum { One, Two };
+
+    var t = true;
+    const x = if (t) Num.Two else unreachable;
+    try expect(x == .Two);
+}