From 56608cbb3d5577d8931830fa02d3e2920925ceab Mon Sep 17 00:00:00 2001
From: Veikka Tuominen <git@vexu.eu>
Date: Tue, 31 May 2022 17:14:37 +0300
Subject: [PATCH] Sema: do not add calls to `returnError` for comptime known
 non-error values

---
 src/Sema.zig | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/Sema.zig b/src/Sema.zig
index ed8391a44d..d4c49973a1 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -13011,10 +13011,13 @@ fn analyzeRet(
     const backend_supports_error_return_tracing =
         sema.mod.comp.bin_file.options.use_llvm;
 
-    if ((sema.fn_ret_ty.zigTypeTag() == .ErrorSet or sema.typeOf(uncasted_operand).zigTypeTag() == .ErrorUnion) and
+    if (sema.fn_ret_ty.isError() and
         sema.mod.comp.bin_file.options.error_return_tracing and
         backend_supports_error_return_tracing)
-    {
+    ret_err: {
+        if (try sema.resolveMaybeUndefVal(block, src, operand)) |ret_val| {
+            if (ret_val.tag() != .@"error") break :ret_err;
+        }
         const return_err_fn = try sema.getBuiltin(block, src, "returnError");
         const unresolved_stack_trace_ty = try sema.getBuiltinType(block, src, "StackTrace");
         const stack_trace_ty = try sema.resolveTypeFields(block, src, unresolved_stack_trace_ty);