Panic when running sema on an error union switch. #25037

const std = @import("std");
const posix = std.posix;
const net = std.net;
const io = std.io;
const OOM = std.mem.Allocator.Error;

const PORT = 7797;

const Error = error{
    /// Transport closed gracefully
    TransportClosed,
    /// Something went wrong with the transport layer.
    /// Details will be logged.
    TransportError,
    OutOfMemory
};

const ClientConnection = struct {
    allocator: std.mem.Allocator,
    // ... deleted fields

    pub fn create(fd: posix.socket_t, addr: net.Address, allocator: std.mem.Allocator) OOM!*ClientConnection {
        _ = fd;
        _ = addr;
        const ccp = try allocator.create(ClientConnection);
        ccp.allocator = allocator;
        return ccp;
    }

    pub fn destroy(self: *ClientConnection) void {
        self.allocator.destroy(self);
    }

    pub fn read_message(self : *ClientConnection) Error![]const u8 {
        _ = self;
        return "minimal repro placeholder";
    }

    pub fn run_forever(self : *ClientConnection) Error!noreturn {
        while (true) {
            const msg = try self.read_message();
            defer self.allocator.free(msg);
            std.log.info("Received message: {s}", .{msg});
        }
    }


    /// Entry point for the lsp thread
    pub fn serve(self : *ClientConnection) void {
        defer self.destroy();
        self.run_forever() catch |err| switch (err) {
            error.TransportClosed => {
                std.log.info("Client {f} disconnected gracefully", .{self.addr});
                return;
            },
            error.TransportError => {
                // error will already have been logged
                return;
            },
            else => {
                std.log.err("Error consuming client data: {t}\n", .{err});
                return;
            },
        };
    }
};

pub fn main() !void {
    // Create a server socket
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    const allocator = gpa.allocator();
    const address = try net.Address.parseIp("0.0.0.0", PORT);

    // Listen for incoming connections
    var server = try address.listen(.{
        .kernel_backlog = 128,
        .reuse_address = true,
    });
    defer server.deinit();

    std.log.info("Server listening on port {d}...", .{PORT});

    // Main event loop
    while (true) {
        // Wait for activity on any of the sockets
        const connection = server.accept() catch |err| {
                std.log.err("Error accepting connection: {t}", .{err});
                continue;
        };
        std.log.info("New connection from {f} on FD-{d}", .{connection.address, connection.stream.handle});
        const client = try ClientConnection.create(
                connection.stream.handle, connection.address, allocator,);
        const thread = try std.Thread.spawn(.{}, ClientConnection.serve, .{client});
        thread.detach();
    }
}

~/zigstuff/zig/build/stage3/bin/zig build
install
└─ install spike3
   └─ compile exe spike3 Debug native failure
error: thread 12972562 panic: reached unreachable code
Analyzing Analyzing 'src/main.zig'
    > %184 = err_union_payload_unsafe(%181) 
      %185 = break(%183, %184)
    For full context, use the command
      zig ast-check -t src/main.zig

  in src/main.zig
    > %183 = switch_block_err_union(%181, err_capture=%186,
        non_err => {%184, %185},
        else => {%217..%236},
        %187 => {%188..%208},
        %209 => {%210..%216}) 

???:?:?: 0x106d71263 in _debug.assert (???)
???:?:?: 0x107b0c367 in _Sema.analyzeBodyInner (???)
???:?:?: 0x1086197c3 in _Sema.analyzeBodyRuntimeBreak (???)
???:?:?: 0x10819be3f in _Sema.zirSwitchBlockErrUnion (???)
???:?:?: 0x107b0032f in _Sema.analyzeBodyInner (???)
???:?:?: 0x107afedcb in _Sema.analyzeFnBody (???)
???:?:?: 0x1076a6edf in _Zcu.PerThread.analyzeFnBodyInner (???)
???:?:?: 0x107363d1b in _Zcu.PerThread.analyzeFuncBody (???)
???:?:?: 0x107181f4b in _Zcu.PerThread.ensureFuncBodyUpToDate (???)
???:?:?: 0x10706604f in _Compilation.processOneJob (???)
???:?:?: 0x106fae8bb in _Compilation.performAllTheWork (???)
???:?:?: 0x106e9a54f in _Compilation.update (???)
???:?:?: 0x106edc1db in _main.serve (???)
???:?:?: 0x106efc08f in _main.buildOutputType (???)
???:?:?: 0x106e5d417 in _main.mainArgs (???)
???:?:?: 0x106e5bd67 in _main.main (???)
???:?:?: 0x106e5bb13 in _main (???)
???:?:?: 0x197462b97 in ??? (???)
???:?:?: 0x0 in ??? (???)

error: the following command terminated unexpectedly:
/Users/edward/zigstuff/zig/build/stage3/bin/zig build-exe -ODebug --dep spike3 -Mroot=/Users/edward/zigstuff/spike3/src/main.zig -Mspike3=/Users/edward/zigstuff/spike3/src/root.zig --cache-dir .zig-cache --global-cache-dir /Users/edward/.cache/zig --name spike3 --zig-lib-dir /Users/edward/zigstuff/zig/build/stage3/lib/zig/ --listen=-

Build Summary: 0/3 steps succeeded; 1 failed
install transitive failure
└─ install spike3 transitive failure
   └─ compile exe spike3 Debug native failure

error: the following build command failed with exit code 1:
.zig-cache/o/c25fe6c3fe28c9518e536a677700f29d/build /Users/edward/zigstuff/zig/build/stage3/bin/zig /Users/edward/zigstuff/zig/build/stage3/lib/zig /Users/edward/zigstuff/spike3 .zig-cache /Users/edward/.cache/zig --seed 0xd218860b -Z7b89149d60b5ad0c