Rollup merge of rust-lang#67148 - Centril:ty-polish, r=estebank

 Refactor type & bounds parsing thoroughly

PR is based on rust-lang#67131 with first one from this PR being ` extract parse_ty_tuple_or_parens`.

Also fixes rust-lang#67146.

r? @estebank

Author: Centril

src/librustc_parse/parser/expr.rs

@@ -90,6 +90,10 @@ impl<'a> Parser<'a> {
         self.parse_expr_res(Restrictions::empty(), None)
     }
 
+    pub(super) fn parse_anon_const_expr(&mut self) -> PResult<'a, AnonConst> {
+        self.parse_expr().map(|value| AnonConst { id: DUMMY_NODE_ID, value })
+    }
+
     fn parse_expr_catch_underscore(&mut self) -> PResult<'a, P<Expr>> {
         match self.parse_expr() {
             Ok(expr) => Ok(expr),
@@ -109,7 +113,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    /// Parses a sequence of expressions bounded by parentheses.
+    /// Parses a sequence of expressions delimited by parentheses.
     fn parse_paren_expr_seq(&mut self) -> PResult<'a, Vec<P<Expr>>> {
         self.parse_paren_comma_seq(|p| {
             p.parse_expr_catch_underscore()
@@ -955,10 +959,7 @@ impl<'a> Parser<'a> {
             let first_expr = self.parse_expr()?;
             if self.eat(&token::Semi) {
                 // Repeating array syntax: `[ 0; 512 ]`
-                let count = AnonConst {
-                    id: DUMMY_NODE_ID,
-                    value: self.parse_expr()?,
-                };
+                let count = self.parse_anon_const_expr()?;
                 self.expect(close)?;
                 ExprKind::Repeat(first_expr, count)
             } else if self.eat(&token::Comma) {

src/librustc_parse/parser/item.rs

@@ -5,7 +5,7 @@ use crate::maybe_whole;
 
 use rustc_errors::{PResult, Applicability, DiagnosticBuilder, StashKey};
 use rustc_error_codes::*;
-use syntax::ast::{self, DUMMY_NODE_ID, Ident, AttrVec, Attribute, AttrKind, AttrStyle, AnonConst};
+use syntax::ast::{self, DUMMY_NODE_ID, Ident, AttrVec, Attribute, AttrKind, AttrStyle};
 use syntax::ast::{AssocItem, AssocItemKind, Item, ItemKind, UseTree, UseTreeKind};
 use syntax::ast::{PathSegment, IsAuto, Constness, IsAsync, Unsafety, Defaultness, Extern, StrLit};
 use syntax::ast::{Visibility, VisibilityKind, Mutability, FnHeader, ForeignItem, ForeignItemKind};
@@ -1317,10 +1317,7 @@ impl<'a> Parser<'a> {
         };
 
         let disr_expr = if self.eat(&token::Eq) {
-            Some(AnonConst {
-                id: DUMMY_NODE_ID,
-                value: self.parse_expr()?,
-            })
+            Some(self.parse_anon_const_expr()?)
         } else {
             None
         };