Auto merge of #66994 - Centril:stmt-polish, r=estebank

refactor expr & stmt parsing + improve recovery

Summary of important changes (best read commit-by-commit, ignoring whitespace changes):

- `AttrVec` is introduces as an alias for `ThinVec<Attribute>`
- `parse_expr_bottom` and `parse_stmt` are thoroughly refactored.
- Extract diagnostics logic for `vec![...]` in a pattern context.
- Recovery is added for `do catch { ... }`
- Recovery is added for `'label: non_block_expr`
- Recovery is added for `var $local`, `auto $local`, and `mut $local`. Fixes #65257.
- Recovery is added for `e1 and e2` and `e1 or e2`.
- ~~`macro_legacy_warnings` is turned into an error (has been a warning for 3 years!)~~
- Fixes #63396 by forward-porting #64105 which now works thanks to added recovery.
- `ui-fulldeps/ast_stmt_expr_attr.rs` is turned into UI and pretty tests.
- Recovery is fixed for `#[attr] if expr {}`

r? @estebank

1 files changed, 1 insertions, 2 deletions

diff --git a/src/librustc_parse/parser/path.rs b/src/librustc_parse/parser/path.rs
index aeba6dd2f67..802d38e2997 100644
--- a/src/librustc_parse/parser/path.rs
+++ b/src/librustc_parse/parser/path.rs
@@ -3,7 +3,6 @@ use crate::maybe_whole;
 use rustc_errors::{PResult, Applicability, pluralize};
 use syntax::ast::{self, QSelf, Path, PathSegment, Ident, ParenthesizedArgs, AngleBracketedArgs};
 use syntax::ast::{AnonConst, GenericArg, AssocTyConstraint, AssocTyConstraintKind, BlockCheckMode};
-use syntax::ThinVec;
 use syntax::token::{self, Token};
 use syntax_pos::source_map::{Span, BytePos};
 use syntax_pos::symbol::{kw, sym};
@@ -400,7 +399,7 @@ impl<'a> Parser<'a> {
                 // Parse const argument.
                 let expr = if let token::OpenDelim(token::Brace) = self.token.kind {
                     self.parse_block_expr(
-                        None, self.token.span, BlockCheckMode::Default, ThinVec::new()
+                        None, self.token.span, BlockCheckMode::Default, ast::AttrVec::new()
                     )?
                 } else if self.token.is_ident() {
                     // FIXME(const_generics): to distinguish between idents for types and consts,