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Rollup merge of #121326 - fmease:detect-empty-leading-where-clauses-on-ty-aliases, r=compiler-errors

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Detect empty leading where clauses on type aliases

1. commit: refactor the AST of type alias where clauses
   * I could no longer bear the look of `.0.1` and `.1.0`
   * Arguably moving `split` out of `TyAlias` into a substruct might not make that much sense from a semantic standpoint since it reprs an index into `TyAlias.predicates` but it's alright and it cleans up the usage sites of `TyAlias`
2. commit: fix an oversight: An empty leading where clause is still a leading where clause
   * semantically reject empty leading where clauses on lazy type aliases
     * e.g., on `#![feature(lazy_type_alias)] type X where = ();`
   * make empty leading where clauses on assoc types trigger lint `deprecated_where_clause_location`
     * e.g., `impl Trait for () { type X where = (); }`
This commit is contained in:
Matthias Krüger 2024-02-29 20:50:02 +01:00 • committed by GitHub
commit dd4ecd1cf4
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18 changed files with 248 additions and 150 deletions
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17
compiler/rustc_parse/src/parser/item.rs
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@ -971,11 +971,17 @@ impl<'a> Parser<'a> {
let after_where_clause = self.parse_where_clause()?;
let where_clauses = (
TyAliasWhereClause(before_where_clause.has_where_token, before_where_clause.span),
TyAliasWhereClause(after_where_clause.has_where_token, after_where_clause.span),
);
let where_predicates_split = before_where_clause.predicates.len();
let where_clauses = TyAliasWhereClauses {
before: TyAliasWhereClause {
has_where_token: before_where_clause.has_where_token,
span: before_where_clause.span,
},
after: TyAliasWhereClause {
has_where_token: after_where_clause.has_where_token,
span: after_where_clause.span,
},
split: before_where_clause.predicates.len(),
};
let mut predicates = before_where_clause.predicates;
predicates.extend(after_where_clause.predicates);
let where_clause = WhereClause {
@ -994,7 +1000,6 @@ impl<'a> Parser<'a> {
defaultness,
generics,
where_clauses,
where_predicates_split,
bounds,
ty,
})),