Inferred error sets in required method implementations crashes stage2 compiler

[phan-do]

Description

On zig master (first seen in 0.10.0-dev.3978+4fd4c733d), stage2 compilations for some programs implementing getty.Serializer (and getty.Deserializer probably) are going into an infinite loop and running forever crashing.

The problem seems to occur when a method implementation is provided for a required method that contains an anytype parameter (e.g., serializeFloat, serializeInt). This causes the infinite loop crash. Providing implementations for methods like serializeBool or serializeNull still works completely fine.

How to Reproduce the Bug

Works

const std = @import("std");
const getty = @import("getty");

const Serializer = struct {
    pub usingnamespace getty.Serializer(
        @This(),
        Ok,
        Error,
        null,
        null,
        null,
        null,
        null,
        .{
            .serializeBool = serializeBool,
        },
    );

    const Ok = void;
    const Error = getty.ser.Error || error{Foobar};

    fn serializeBool(_: @This(), value: bool) !Ok {
        std.debug.print("{}\n", .{value});
    }
};

pub fn main() anyerror!void {
    var s = Serializer{};
    const serializer = s.serializer();

    try getty.serialize(null, true, serializer);
}

Doesn't Work

const std = @import("std");
const getty = @import("getty");

const Serializer = struct {
    pub usingnamespace getty.Serializer(
        @This(),
        Ok,
        Error,
        null,
        null,
        null,
        null,
        null,
        .{
            .serializeInt = serializeInt,
        },
    );

    const Ok = void;
    const Error = getty.ser.Error || error{Foobar};

    fn serializeInt(_: @This(), value: anytype) !Ok {
        std.debug.print("{}\n", .{value});
    }
};

pub fn main() anyerror!void {
    var s = Serializer{};
    const serializer = s.serializer();

    try getty.serialize(null, 123, serializer);
}

$ zig build run
zig build-exe test Debug native: error: thread 431519 panic: attempt to unwrap error
Unable to dump stack trace: debug info stripped

zig build-exe test Debug native: error: the following command terminated unexpectedly:
/Users/jason/.asdf/installs/zig/master/zig build-exe /Users/jason/Projects/Personal/test/src/main.zig --cache-dir /Users/jason/Projects/Personal/test/zig-cache --global-cache-dir /Users/jason/.cache/zig --name test --mod getty::/Users/jason/.cache/zig/p/1220c649e62d6bb0e07ac6b02711f76254f1dd1875859ad075873d248fb820f68d66/src/getty.zig --deps getty --listen=-
Build Summary: 0/5 steps succeeded; 1 failed (disable with -fno-summary)
run transitive failure
└─ run test transitive failure
   ├─ zig build-exe test Debug native failure
   └─ install transitive failure
      └─ install test transitive failure
         └─ zig build-exe test Debug native (reused)
error: the following build command failed with exit code 1:
/Users/jason/Projects/Personal/test/zig-cache/o/ee1be17a562f060aa4ae0c496b5dcfcc/build /Users/jason/.asdf/installs/zig/master/zig /Users/jason/Projects/Personal/test /Users/jason/Projects/Personal/test/zig-cache /Users/jason/.cache/zig run

Additional Context

Compiling with stage1 fixes the problem. So if you need a workaround for now, the following should work for you:

zig build -fstage1 run

[phan-do]

The problem is apparently inferred error sets. I guess you can't use them anymore when implementing methods that have anytype parameters?

Making the error set explicit fixes this issue.

[phan-do]

Relevant issue in the ziglang repo: ziglang/zig#12806