1 files changed, 22 insertions, 12 deletions
diff --git a/std/special/start.zig b/std/special/start.zig
index 76dfe420c4..f2fe27e26c 100644
--- a/std/special/start.zig
+++ b/std/special/start.zig
@@ -128,6 +128,9 @@ extern fn main(c_argc: i32, c_argv: [*][*]u8, c_envp: [*]?[*]u8) i32 {
 // This is marked inline because for some reason LLVM in release mode fails to inline it,
 // and we want fewer call frames in stack traces.
 inline fn callMain() u8 {
+    // General error message for a malformed return type
+    const compile_err_prefix = "expected return type of main to be 'u8', 'noreturn', 'void', '!void', or '!u8', found '";
+    const compile_err = compile_err_prefix ++ @typeName(@typeOf(root.main).ReturnType) ++ "'";
     switch (@typeId(@typeOf(root.main).ReturnType)) {
         .NoReturn => {
             root.main();
@@ -138,23 +141,30 @@ inline fn callMain() u8 {
         },
         .Int => {
             if (@typeOf(root.main).ReturnType.bit_count != 8) {
-                @compileError("expected return type of main to be 'u8', 'noreturn', 'void', or '!void'");
+                @compileError(compile_err);
             }
             return root.main();
         },
-        .ErrorUnion => {
-            root.main() catch |err| {
-                std.debug.warn("error: {}\n", @errorName(err));
-                if (builtin.os != builtin.Os.zen) {
-                    if (@errorReturnTrace()) |trace| {
-                        std.debug.dumpStackTrace(trace.*);
+        builtin.TypeId.ErrorUnion => {
+            const PayloadType = @typeOf(root.main).ReturnType.Payload;
+            // In this case the error should include the payload type
+            const payload_err = compile_err_prefix ++ "!" ++ @typeName(PayloadType) ++ "'";
+            // If the payload is void or a u8
+            if (@typeId(PayloadType) == builtin.TypeId.Void or (@typeId(PayloadType) == builtin.TypeId.Int and PayloadType.bit_count == 8)) {
+                const tmp = root.main() catch |err| {
+                    std.debug.warn("error: {}\n", @errorName(err));
+                    if (builtin.os != builtin.Os.zen) {
+                        if (@errorReturnTrace()) |trace| {
+                            std.debug.dumpStackTrace(trace.*);
+                        }
                     }
-                }
-                return 1;
-            };
-            return 0;
+                    return 1;
+                };
+                // If main didn't error, return 0 or the exit code
+                return if (PayloadType == void) 0 else tmp;
+            } else @compileError(payload_err);
         },
-        else => @compileError("expected return type of main to be 'u8', 'noreturn', 'void', or '!void'"),
+        else => @compileError(compile_err),
     }
 }