Auto merge of #99263 - compiler-errors:issue-99261, r=jyn514

Fix ICE in `named_arguments_used_positionally` lint

Fixes #99261
Fixes #99289
Fixes #99284
Fixes #99273
Fixes #99297
Fixes #99271

This match pattern:

```
 FormatSpec { width: Count::CountIsName(s, _), .. }
| FormatSpec { precision: Count::CountIsName(s, _), .. }
```

does not account for when both `width` and `precision` are both `Count::CountIsName`, so split the check for these two fields into two separate `if let`.

Also, remove any future potential for ICEs by removing the index operator altogether.

---

It is still suspicious that this indexing was broken and caused the ICE, as opposed to just causing a spurious lint message.

cc `@PrestonFrom,` who may be familiar with this code because of implementing the lint this touches, perhaps you'd like to look into why named arguments in `FormatSpec.precision` seem to have indices that don't correspond to a span in `Context.arg_spans`?

Edit: Opened #99265 to track a (related?) incorrect argument indexing issue.

1 files changed, 17 insertions, 0 deletions

diff --git a/src/test/ui/macros/issue-99261.rs b/src/test/ui/macros/issue-99261.rs
new file mode 100644
index 00000000000..40d26d08cba
--- /dev/null
+++ b/src/test/ui/macros/issue-99261.rs
@@ -0,0 +1,17 @@
+// check-pass
+
+#![deny(named_arguments_used_positionally)]
+
+fn main() {
+    let value: f64 = 314.15926;
+    let digits_before_decimal = 1;
+    let digits_after_decimal = 2;
+    let width = digits_before_decimal + 1 + digits_after_decimal;
+
+    println!(
+        "{value:0>width$.digits_after_decimal$}",
+        value = value,
+        width = width,
+        digits_after_decimal = digits_after_decimal,
+    );
+}