Sema: provide source location when analyzing panic handler

The panic handler decl_val was previously given a `unneeded` source
location, which was then added to the reference trace, resulting in a
crash if the source location was used in the reference trace. This
commit makes two trivial changes:

* Don't add unneeded source locations to the ref table (panic in debug, silently ignore in release)
* Pass a real source location when analyzing the panic handler

1 files changed, 17 insertions, 0 deletions

diff --git a/test/cases/compile_errors/panic_has_source_location.zig b/test/cases/compile_errors/panic_has_source_location.zig
new file mode 100644
index 0000000000..6e9d16d76d
--- /dev/null
+++ b/test/cases/compile_errors/panic_has_source_location.zig
@@ -0,0 +1,17 @@
+const std = @import("std");
+
+export fn foo() void {
+    // This should appear in the reference trace
+    // (and definitely shouldn't crash due to an unneeded source location!)
+    @panic("oh no");
+}
+
+pub fn panic(_: []const u8, _: ?*std.builtin.StackTrace, _: ?usize) noreturn {
+    @compileError("panic");
+}
+
+// error
+// backend=stage2
+// target=native
+//
+// :10:5: error: panic