stage2 crash in astgen due to errors getting ignored

[g-w1]

This crashes astgen:

fn ChaChaLetsCrashAstGen() type {
    return struct {
        pub fn AHHHHHHHHHHHHHHHHHHHHHHHHHHHHH() void {
            const bruh = 1091290;
            const bruh = 1091290;
        }
    };
}

❯ ./zig ast-check test.zig                                                                                                                                                                                                                   
thread 4039 panic: reached unreachable code
/home/jacob/dev/zig/src/AstGen.zig:2137:27: 0xee4458 in AstGen.genDefers (zig1)
            .namespace => unreachable,
                          ^
/home/jacob/dev/zig/src/AstGen.zig:6013:22: 0xdba900 in AstGen.ret (zig1)
        try genDefers(gz, &astgen.fn_block.?.base, scope, .none);
                     ^
/home/jacob/dev/zig/src/AstGen.zig:628:33: 0xc98c9b in AstGen.expr (zig1)
        .@"return" => return ret(gz, scope, node),
                                ^
/home/jacob/dev/zig/src/AstGen.zig:1821:41: 0xeeece4 in AstGen.unusedResultExpr (zig1)
    const maybe_unused_result = try expr(gz, scope, .none, statement);
                                        ^
/home/jacob/dev/zig/src/AstGen.zig:1809:41: 0xee8a7b in AstGen.blockExprStmts (zig1)
            else => try unusedResultExpr(gz, scope, statement),
                                        ^
/home/jacob/dev/zig/src/AstGen.zig:1646:23: 0xdc1b7d in AstGen.blockExpr (zig1)
    try blockExprStmts(gz, scope, block_node, statements);
                      ^
/home/jacob/dev/zig/src/AstGen.zig:718:33: 0xc9d009 in AstGen.expr (zig1)
                return blockExpr(gz, scope, rl, node, statements[0..1]);
                                ^
/home/jacob/dev/zig/src/AstGen.zig:2925:25: 0xc9245d in AstGen.fnDecl (zig1)
            _ = try expr(&fn_gz, params_scope, .none, body_node);
                        ^
/home/jacob/dev/zig/src/AstGen.zig:3390:38: 0xb5541c in AstGen.structDeclInner (zig1)
                        astgen.fnDecl(gz, &namespace.base, &wip_decls, member_node, body, tree.fnProtoSimple(&params, fn_proto)) catch |err| switch (err) {The fact that you have shadowing is not the point. I think a lot of other errors could have worked, shadowing is just the first one I thought of.


                                     ^
/home/jacob/dev/zig/src/AstGen.zig:107:31: 0x9a8f15 in AstGen.generate (zig1)
    if (AstGen.structDeclInner(
                              ^
/home/jacob/dev/zig/src/main.zig:3678:35: 0x91ed82 in main.cmdAstCheck (zig1)
    file.zir = try AstGen.generate(gpa, file.tree);
                                  ^
/home/jacob/dev/zig/src/main.zig:243:27: 0x8a39c6 in main.mainArgs (zig1)
        return cmdAstCheck(gpa, arena, cmd_args);
                          ^
/home/jacob/dev/zig/src/stage1.zig:45:24: 0x8a20f9 in main (zig1)
        stage2.mainArgs(gpa, arena, args) catch unreachable;
                       ^
Aborted (core dumped)

Segfaults on tarball zig, or prints stack trace on debug zig

The fact that you have shadowing is not the point. I think a lot of other errors could have worked, shadowing is just the first one I thought of.

Ok, so why does this trigger a bug, heres what I think

.fn_proto_simple => {
    var params: [1]ast.Node.Index = undefined;
    astgen.fnDecl(gz, &namespace.base, &wip_decls, member_node, body, tree.fnProtoSimple(&params, fn_proto)) catch |err| switch (err) {
        error.OutOfMemory => return error.OutOfMemory,
        error.AnalysisFail => {},
    };
    continue;
},

When we have this code, it ignores error.AnalysisFail. This is fine for most things, but when you have a function that returns a
struct, it kinda breaks down. It keeps trying to do analyze to the struct, since, it effectively ignored the error. Then it does
weird stuff to invalid zir, which is a no-no.

This is blocking my unused vars pr. I can't really think of a fix for this.