Deduplicate mismatched delimiter errors Delay unmatched delimiter errors until after the parser has run to deduplicate them when parsing and attempt recovering intelligently. Second attempt at #54029, follow up to #53949. Fix #31528.
The syntax
crate contains those things concerned purely with syntax
– that is, the AST ("abstract syntax tree"), parser, pretty-printer,
lexer, macro expander, and utilities for traversing ASTs.
For more information about how these things work in rustc, see the rustc guide: