Auto merge of #121589 - bvanjoi:fix-98291, r=petrochenkov

delay expand macro bang when there has indeterminate path

Related #98291

I will attempt to clarify the root problem through several examples:

Firstly,

```rs
// rustc code.rs --edition=2018

macro_rules! wrap {
    () => {
        macro_rules! _a {
            () => {
                "Hello world"
            };
        }
    };
}

wrap!();

use _a as a;

fn main() {
    format_args!(_a!());
}
```

The above case will compile successfully because `_a` is defined after the `wrap` expaned, ensuring `_a` can be resolved without any issues.

And,

```rs
// rustc code.rs --edition=2018

macro_rules! wrap {
    () => {
        macro_rules! _a {
            () => {
                "Hello world"
            };
        }
    };
}

wrap!();

use _a as a;

fn main() {
    format_args!("{}", a!());
}
```

The above example will also compile successfully because the `parse_args` in `expand_format_args_impl` will return a value `MacroInput { fmtstr: Expr::Lit::Str, args: [Expr::MacroCall]}`. Since the graph for `args` will be build lately, `a` will eventually be resolved.

However, in the case of:

```rs
// rustc code.rs --edition=2018

macro_rules! wrap {
    () => {
        macro_rules! _a {
            () => {
                "Hello world"
            };
        }
    };
}

wrap!();

use _a as a;

fn main() {
    format_args!(a!());
}
```

The result of `parse_args` is `MacroInput {fmtstr: Expr::Lit::Macro, args: [] }`, we attempt to expand `fmtstr` **eagerly** within `expr_to_spanned_string`. Although we have recorded `(root, _a)` into resolutions, `use _a as a` is an indeterminate import, which will not try to resolve under the conditions of `expander.monotonic = false`.

Therefore, I've altered the strategy for resolving indeterminate imports, ensuring it will also resolve during eager expansion. This could be a significant change to the resolution infra. However, I think it's acceptable if the goal of avoiding resolution under eager expansion is to save time.

r? `@petrochenkov`

0 files changed, 0 insertions, 0 deletions