broken LLVM module with this code

[marler8997]

pub const Struct = struct {
    pub fn method(self: *@This()) ![]const u8 {
       return error.a;
    }
};
pub fn main() void {
    const optionalString : ?[]const u8 = "hello";
    if (optionalString) |s| {
        var foo = Struct {};
        s = foo.method();
    }
}

> zig build-exe bug.zig
broken LLVM module found: Call parameter type does not match function signature!
%"[]u8"* @328
 { %"[]u8", i16 }*  call fastcc void @Struct.method(%"[]u8"* sret @328, %builtin.StackTrace* %error_return_trace), !dbg !14121

Unable to dump stack trace: debug info stripped
Aborted (core dumped)

@gustavolsson provided another example that is a bit more reduced:

fn errorAndSlice() ![]const u8 {
    return error.a;
}

fn indirect() []const u8 {
    return errorAndSlice();
}

test "causes LLVM broken module" {
    var slice: []const u8 = indirect(); // gets to code generation and fails with LLVM error
}

[gustavolsson]

I have the same problem with slices and error sets:

fn errorAndSlice() ![]const u8 {
    return error.a;
}

fn indirect() []const u8 {
    return errorAndSlice();
}

// test "catches error" {
//     var slice: []const u8 = errorAndSlice(); // properly catches the mistake (no error handling)
// }

test "doesnt catch error" {
    var slice: []const u8 = indirect(); // gets to code generation and fails with LLVM error
}

Note that this does work with primitive types:

fn errorAndNumber() !u8 {
    return error.a;
}

fn indirect() u8 {
    return errorAndNumber();
}

test "catches error" {
    var num: u8 = errorAndNumber(); // properly catches the mistake (no error handling)
}

test "doesnt catch error" {
    var num: u8 = indirect(); // properly catches the mistake (no error handling)
}

[marler8997]

@gustavolsson yeah it looks like it's probably the same issue. Zig doesn't seem to be detecting that an error union with a slice being assigned to a normal slice without an error union is an error. Since Zig doesn't detect it, the error doesn't get caught until LLVM takes over.

I tried u8 as well in my example and Zig detects the error in that case, so the type matters for some reason.

[marler8997]

Latest compiler seems to correctly detect this as a compile error now, thanks for fixing!