debug printing ZIR of this zig code crashes stage2

[andrewrk]

fn ArrayList(comptime T: type) type {
    return struct {
        x: T,

        fn foo(self: @This()) void {
            const a = self;
            const b = T;
        }
    };
}

[nix-shell:~/dev/zig/build-release]$ ./zig-out/bin/zig astgen test.zig
# Source bytes:       182B
# Tokens:             43 (239B)
# AST Nodes:          19 (367B)
# Total ZIR bytes:    571B
# Instructions:       22 (198B)
# String Table Bytes: 29B
# Extra Data Items:   70 (280B)
%21 = extended(struct_decl(parent, Auto, {
  [63] ArrayList line(0) hash(4d7f75c961c3193e0dc2fa1aafb225e1): %0 = block_inline({
    %19 = func([@Ref.type_type], @Ref.type_type, {
      %1 = arg("T") token_offset:1:23
      %2 = dbg_stmt(1, 4)
      %3 = extended(ret_type()) node_offset:2:5
      %15 = extended(struct_decl(anon, Auto, {
        [31] foo line(4) hash(3c92c018eb12595917908fd6fd000f2b): %5 = block_inline({
          %6 = extended(this()) node_offset:5:22
          %7 = as_node(@Ref.type_type, %6) node_offset:5:22
          %13 = func([%7], @Ref.void_type, {
            %8 = arg("self") token_offset:5:16
            %9 = dbg_stmt(1, 12)
            %10 = dbg_stmt(2, 12)
            %11 = decl_val("T") token_offset:7:23
            %12 = ret_coerce(@Ref.void_value) token_offset:8:9
          }) (lbrace=0:27,rbrace=3:8) node_offset:5:9
          %14 = break_inline(%5, %13)
        }) node_offset:5:9
      }, {
        %4 = as_node(@Ref.type_type, %1) thread 2088 panic: index out of bounds
/home/andy/dev/zig/src/Module.zig:1500:46: 0x489598 in Module.SrcLoc.byteOffset (zig)
                const tok_index = main_tokens[node];
                                             ^
/home/andy/dev/zig/src/Zir.zig:4448:48: 0x581d8a in Zir.Writer.writeSrc (zig)
        const abs_byte_off = src_loc.byteOffset(self.gpa) catch unreachable;
                                               ^
/home/andy/dev/zig/src/Zir.zig:4176:26: 0x4ba727 in Zir.Writer.writeAs (zig)
        try self.writeSrc(stream, inst_data.src());
                         ^
/home/andy/dev/zig/src/Zir.zig:3039:41: 0x4b1ea2 in Zir.Writer.writeInstToStream (zig)
            .as_node => try self.writeAs(stream, inst),
                                        ^
/home/andy/dev/zig/src/Zir.zig:4466:39: 0x581ffd in Zir.Writer.writeBody (zig)
            try self.writeInstToStream(stream, inst);
                                      ^
/home/andy/dev/zig/src/Zir.zig:3549:35: 0x58e105 in Zir.Writer.writeStructDecl (zig)
                try self.writeBody(stream, body);
                                  ^
/home/andy/dev/zig/src/Zir.zig:3105:53: 0x4bb691 in Zir.Writer.writeExtended (zig)
            .struct_decl => try self.writeStructDecl(stream, extended),
                                                    ^
/home/andy/dev/zig/src/Zir.zig:3073:48: 0x4b2213 in Zir.Writer.writeInstToStream (zig)
            .extended => try self.writeExtended(stream, inst),
                                               ^
/home/andy/dev/zig/src/Zir.zig:4466:39: 0x581ffd in Zir.Writer.writeBody (zig)
            try self.writeInstToStream(stream, inst);
                                      ^
/home/andy/dev/zig/src/Zir.zig:4379:31: 0x58adc2 in Zir.Writer.writeFuncCommon (zig)
            try self.writeBody(stream, body);
                              ^
/home/andy/dev/zig/src/Zir.zig:4217:36: 0x4bac5e in Zir.Writer.writeFunc (zig)
        return self.writeFuncCommon(
                                   ^
/home/andy/dev/zig/src/Zir.zig:3058:40: 0x4b1fec in Zir.Writer.writeInstToStream (zig)
            .func => try self.writeFunc(stream, inst, false),
                                       ^
/home/andy/dev/zig/src/Zir.zig:4466:39: 0x581ffd in Zir.Writer.writeBody (zig)
            try self.writeInstToStream(stream, inst);
                                      ^
/home/andy/dev/zig/src/Zir.zig:3467:27: 0x5869c5 in Zir.Writer.writePlNodeBlockWithoutSrc (zig)
        try self.writeBody(stream, body);
                          ^
/home/andy/dev/zig/src/Zir.zig:3826:48: 0x5880c8 in Zir.Writer.writeDecls (zig)
            try self.writePlNodeBlockWithoutSrc(stream, decl_index);
                                               ^
/home/andy/dev/zig/src/Zir.zig:3531:46: 0x58eaac in Zir.Writer.writeStructDecl (zig)
            extra_index = try self.writeDecls(stream, decls_len, extra_index);
                                             ^
/home/andy/dev/zig/src/Zir.zig:3105:53: 0x4bb691 in Zir.Writer.writeExtended (zig)
            .struct_decl => try self.writeStructDecl(stream, extended),
                                                    ^
/home/andy/dev/zig/src/Zir.zig:3073:48: 0x4b2213 in Zir.Writer.writeInstToStream (zig)
            .extended => try self.writeExtended(stream, inst),
                                               ^
/home/andy/dev/zig/src/Zir.zig:136:33: 0x3bf8ba in Zir.renderAsTextToFile (zig)
    try writer.writeInstToStream(fs_file.writer(), main_struct_inst);
                                ^
/home/andy/dev/zig/src/main.zig:3662:34: 0x39b269 in cmdAstgen (zig)
    return Zir.renderAsTextToFile(gpa, &file, io.getStdOut());
                                 ^
/home/andy/dev/zig/src/main.zig:234:25: 0x33e266 in mainArgs (zig)
        return cmdAstgen(gpa, arena, cmd_args);
                        ^
/home/andy/dev/zig/src/main.zig:141:20: 0x335860 in main (zig)
    return mainArgs(gpa, arena, args);
                   ^
/home/andy/dev/zig/lib/std/start.zig:458:37: 0x32e0fa in std.start.callMain (zig)
            const result = root.main() catch |err| {
                                    ^
/home/andy/dev/zig/lib/std/start.zig:400:12: 0x31225e in std.start.callMainWithArgs (zig)
    return @call(.{ .modifier = .always_inline }, callMain, .{});
           ^
/home/andy/dev/zig/lib/std/start.zig:318:17: 0x311245 in std.start.posixCallMainAndExit (zig)
    std.os.exit(@call(.{ .modifier = .always_inline }, callMainWithArgs, .{ argc, argv, envp }));
                ^
/home/andy/dev/zig/lib/std/start.zig:244:5: 0x310fa2 in std.start._start (zig)
    @call(.{ .modifier = .never_inline }, posixCallMainAndExit, .{});
    ^
Aborted (core dumped)

[andrewrk]

Reduced test case:

fn a() type {
    return struct { b: *i32 };
}