Rollup merge of rust-lang#126851 - nnethercote:NtExprKind-NtPatKind, r=compiler-errors

Rework pattern and expression nonterminal kinds.

Some tweaks to `NonterminalKind` that will assist with rust-lang#124141. Details in the individual commits.

r? compiler-errors
cc ```@eholk```

Author: matthiaskrgr

src/parse/macros/mod.rs

@@ -1,4 +1,4 @@
-use rustc_ast::token::{Delimiter, NonterminalKind, TokenKind};
+use rustc_ast::token::{Delimiter, NonterminalKind, NtExprKind::*, NtPatKind::*, TokenKind};
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast::{ast, ptr};
 use rustc_parse::parser::{ForceCollect, Parser, Recovery};
@@ -48,7 +48,7 @@ fn parse_macro_arg<'a, 'b: 'a>(parser: &'a mut Parser<'b>) -> Option<MacroArg> {
 
     parse_macro_arg!(
         Expr,
-        NonterminalKind::Expr,
+        NonterminalKind::Expr(Expr),
         |parser: &mut Parser<'b>| parser.parse_expr(),
         |x: ptr::P<ast::Expr>| Some(x)
     );
@@ -60,7 +60,7 @@ fn parse_macro_arg<'a, 'b: 'a>(parser: &'a mut Parser<'b>) -> Option<MacroArg> {
     );
     parse_macro_arg!(
         Pat,
-        NonterminalKind::PatParam { inferred: false },
+        NonterminalKind::Pat(PatParam { inferred: false }),
         |parser: &mut Parser<'b>| parser.parse_pat_no_top_alt(None, None),
         |x: ptr::P<ast::Pat>| Some(x)
     );