Steering issue #7

[lnicola]

Zulip meeting link. For the next sprint, there's some proc macro tech debt we'd like to address:

• Replace TokenMap with an abstraction that matches reality #9403
• Implement missing parts of the proc macro API #10368
• thread '<unnamed>' panicked at 'index out of bounds: the len is 1 but the index is 1', crates/hir_def/src/nameres/path_resolution.rs:385:33 #10084
• (bonus) Investigate completion and highlight performance #10369

Previous issue: #9925
Next issue: #10724