Inline can_begin_literal_maybe_minus call into two places.

It's clearer this way, because the `Interpolated` cases in
`can_begin_const_arg` and `is_pat_range_end_start` are more permissive
than the `Interpolated` cases in `can_begin_literal_maybe_minus`.

Author: nnethercote

compiler/rustc_ast/src/token.rs

@@ -558,9 +558,10 @@ impl Token {
     /// Returns `true` if the token can appear at the start of a const param.
     pub fn can_begin_const_arg(&self) -> bool {
         match self.kind {
-            OpenDelim(Delimiter::Brace) => true,
+            OpenDelim(Delimiter::Brace) | Literal(..) | BinOp(Minus) => true,
+            Ident(name, IdentIsRaw::No) if name.is_bool_lit() => true,
             Interpolated(ref nt) => matches!(&**nt, NtExpr(..) | NtBlock(..) | NtLiteral(..)),
-            _ => self.can_begin_literal_maybe_minus(),
+            _ => false,
         }
     }
 

compiler/rustc_parse/src/parser/pat.rs

@@ -939,7 +939,8 @@ impl<'a> Parser<'a> {
             || self.look_ahead(dist, |t| {
                 t.is_path_start() // e.g. `MY_CONST`;
                 || t.kind == token::Dot // e.g. `.5` for recovery;
-                || t.can_begin_literal_maybe_minus() // e.g. `42`.
+                || matches!(t.kind, token::Literal(..) | token::BinOp(token::Minus))
+                || t.is_bool_lit()
                 || t.is_whole_expr()
                 || t.is_lifetime() // recover `'a` instead of `'a'`
                 || (self.may_recover() // recover leading `(`