Merge branch 'SamTebbs33-main-return'

std/special/start.zig

@@ -125,10 +125,13 @@ extern fn main(c_argc: i32, c_argv: [*][*]u8, c_envp: [*]?[*]u8) i32 {
     return callMainWithArgs(@intCast(usize, c_argc), c_argv, envp);
 }
 
+// General error message for a malformed return type
+const bad_main_ret = "expected return type of main to be 'void', '!void', 'noreturn', 'u8', or '!u8'";
+
 // 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 {
-    switch (@typeId(@typeOf(root.main).ReturnType)) {
+    switch (@typeInfo(@typeOf(root.main).ReturnType)) {
         .NoReturn => {
             root.main();
         },
@@ -136,25 +139,32 @@ inline fn callMain() u8 {
             root.main();
             return 0;
         },
-        .Int => {
-            if (@typeOf(root.main).ReturnType.bit_count != 8) {
-                @compileError("expected return type of main to be 'u8', 'noreturn', 'void', or '!void'");
+        .Int => |info| {
+            if (info.bits != 8) {
+                @compileError(bad_main_ret);
             }
             return root.main();
         },
         .ErrorUnion => {
-            root.main() catch |err| {
+            const result = root.main() catch |err| {
                 std.debug.warn("error: {}\n", @errorName(err));
-                if (builtin.os != builtin.Os.zen) {
-                    if (@errorReturnTrace()) |trace| {
-                        std.debug.dumpStackTrace(trace.*);
-                    }
+                if (@errorReturnTrace()) |trace| {
+                    std.debug.dumpStackTrace(trace.*);
                 }
                 return 1;
             };
-            return 0;
+            switch (@typeInfo(@typeOf(result))) {
+                .Void => return 0,
+                .Int => |info| {
+                    if (info.bits != 8) {
+                        @compileError(bad_main_ret);
+                    }
+                    return result;
+                },
+                else => @compileError(bad_main_ret),
+            }
         },
-        else => @compileError("expected return type of main to be 'u8', 'noreturn', 'void', or '!void'"),
+        else => @compileError(bad_main_ret),
     }
 }
 

test/build_examples.zig

@@ -7,6 +7,8 @@ pub fn addCases(cases: *tests.BuildExamplesContext) void {
     cases.addC("example/hello_world/hello_libc.zig");
     cases.add("example/cat/main.zig");
     cases.add("example/guess_number/main.zig");
+    cases.add("test/standalone/main_return_error/error_u8.zig");
+    cases.add("test/standalone/main_return_error/error_u8_non_zero.zig");
     cases.addBuildFile("test/standalone/main_pkg_path/build.zig");
     cases.addBuildFile("example/shared_library/build.zig");
     cases.addBuildFile("example/mix_o_files/build.zig");

test/compile_errors.zig

@@ -2247,7 +2247,7 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
         "wrong return type for main",
         \\pub fn main() f32 { }
     ,
-        "error: expected return type of main to be 'u8', 'noreturn', 'void', or '!void'",
+        "error: expected return type of main to be 'void', '!void', 'noreturn', 'u8', or '!u8'",
     );
 
     cases.add(
@@ -2255,7 +2255,7 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
         \\pub fn main() ??void {
         \\}
     ,
-        "error: expected return type of main to be 'u8', 'noreturn', 'void', or '!void'",
+        "error: expected return type of main to be 'void', '!void', 'noreturn', 'u8', or '!u8'",
     );
 
     cases.add(

test/standalone/main_return_error/error_u8.zig

@@ -0,0 +1,7 @@
+const Err = error {
+    Foo
+};
+
+pub fn main() !u8 {
+    return Err.Foo;
+}

test/standalone/main_return_error/error_u8_non_zero.zig

@@ -0,0 +1,8 @@
+const Err = error { Foo };
+
+fn foo() u8 { var x = @intCast(u8, 9); return x; }
+
+pub fn main() !u8 {
+    if (foo() == 7) return Err.Foo;
+    return 123;
+}