From fb481d0bf81df7b0ce9afde5cd615133d9895726 Mon Sep 17 00:00:00 2001
From: mlugg <mlugg@mlugg.co.uk>
Date: Tue, 4 Feb 2025 15:05:40 +0000
Subject: [PATCH] Zcu: fix bug clearing compile errors

And add an assertion in safe builds that our initial check is actually
correct.
---
 src/Zcu/PerThread.zig | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/src/Zcu/PerThread.zig b/src/Zcu/PerThread.zig
index a28a2ae7ec..32372bf597 100644
--- a/src/Zcu/PerThread.zig
+++ b/src/Zcu/PerThread.zig
@@ -2795,21 +2795,32 @@ pub fn getErrorValueFromSlice(pt: Zcu.PerThread, name: []const u8) Allocator.Err
 /// Removes any entry from `Zcu.failed_files` associated with `file`. Acquires `Compilation.mutex` as needed.
 /// `file.zir` must be unchanged from the last update, as it is used to determine if there is such an entry.
 fn lockAndClearFileCompileError(pt: Zcu.PerThread, file: *Zcu.File) void {
-    switch (file.getMode()) {
-        .zig => {
-            const zir = file.zir orelse return;
-            if (!zir.hasCompileErrors()) return;
-        },
-        .zon => {
-            const zoir = file.zoir orelse return;
-            if (!zoir.hasCompileErrors()) return;
+    const maybe_has_error = switch (file.status) {
+        .never_loaded => false,
+        .retryable_failure => true,
+        .astgen_failure => true,
+        .success => switch (file.getMode()) {
+            .zig => has_error: {
+                const zir = file.zir orelse break :has_error false;
+                break :has_error zir.hasCompileErrors();
+            },
+            .zon => has_error: {
+                const zoir = file.zoir orelse break :has_error false;
+                break :has_error zoir.hasCompileErrors();
+            },
         },
+    };
+
+    // If runtime safety is on, let's quickly lock the mutex and check anyway.
+    if (!maybe_has_error and !std.debug.runtime_safety) {
+        return;
     }
 
     pt.zcu.comp.mutex.lock();
     defer pt.zcu.comp.mutex.unlock();
     if (pt.zcu.failed_files.fetchSwapRemove(file)) |kv| {
-        if (kv.value) |msg| msg.destroy(pt.zcu.gpa); // Delete previous error message.
+        assert(maybe_has_error); // the runtime safety case above
+        if (kv.value) |msg| msg.destroy(pt.zcu.gpa); // delete previous error message
     }
 }