fix: prevent ICE on lifetime-only macro arguments

[saberoueslati]

Fixes #7034.

Problem

Malformed macro arguments ending in &'a trigger rustc’s pattern parser, which creates an empty suggestion span at EOF and trips a debug assertion. &&'a variants are also affected because && is parsed as nested & tokens.

Fix

Skip speculative pattern parsing when a run of &/&& tokens is followed by a lifetime. Valid types remain unaffected, and rustfmt uses its existing unparseable-macro fallback.

Testing

Added &'a, &&'a, and &&&'a cases to dont_emit_ICE. Full cargo test passes.

• I did not use an LLM to create a change in this PR.
• I used an LLM to create a change in this PR, and I have explained below how it was used.

LLM was used to understand the issue and as an extra reviewer for my code

[ytmimi]

I wonder if this is the right approach. The root of the issue is in the rustc parser when debug-assertions are enabled. I feel like a more appropriate fix would be to address the source of the issue in rust-lang/rust than try to side step the issue by conditionally avoiding parser.parse_pat_no_top_alt.