Rollup merge of #123395 - compiler-errors:postfix-matches-fixes-2, r=petrochenkov

More postfix match fixes

These affect diagnostics only, as far as I can tell. I'm too lazy to come up with UI tests, but I could be convinced otherwise.

Specifically, I think changing the precedence computation actually doesn't change anything, but tweaking `contains_exterior_struct_lit` does mean that some diagnostics will begin parenthesizing `S {}.match {}`.

Author: matthiaskrgr

compiler/rustc_ast/src/ast.rs

@@ -1276,7 +1276,8 @@ impl Expr {
             ExprKind::While(..) => ExprPrecedence::While,
             ExprKind::ForLoop { .. } => ExprPrecedence::ForLoop,
             ExprKind::Loop(..) => ExprPrecedence::Loop,
-            ExprKind::Match(..) => ExprPrecedence::Match,
+            ExprKind::Match(_, _, MatchKind::Prefix) => ExprPrecedence::Match,
+            ExprKind::Match(_, _, MatchKind::Postfix) => ExprPrecedence::PostfixMatch,
             ExprKind::Closure(..) => ExprPrecedence::Closure,
             ExprKind::Block(..) => ExprPrecedence::Block,
             ExprKind::TryBlock(..) => ExprPrecedence::TryBlock,

compiler/rustc_ast/src/util/parser.rs

@@ -281,6 +281,7 @@ pub enum ExprPrecedence {
     ForLoop,
     Loop,
     Match,
+    PostfixMatch,
     ConstBlock,
     Block,
     TryBlock,
@@ -334,7 +335,8 @@ impl ExprPrecedence {
             | ExprPrecedence::InlineAsm
             | ExprPrecedence::Mac
             | ExprPrecedence::FormatArgs
-            | ExprPrecedence::OffsetOf => PREC_POSTFIX,
+            | ExprPrecedence::OffsetOf
+            | ExprPrecedence::PostfixMatch => PREC_POSTFIX,
 
             // Never need parens
             ExprPrecedence::Array
@@ -390,7 +392,8 @@ pub fn contains_exterior_struct_lit(value: &ast::Expr) -> bool {
         | ast::ExprKind::Cast(x, _)
         | ast::ExprKind::Type(x, _)
         | ast::ExprKind::Field(x, _)
-        | ast::ExprKind::Index(x, _, _) => {
+        | ast::ExprKind::Index(x, _, _)
+        | ast::ExprKind::Match(x, _, ast::MatchKind::Postfix) => {
             // &X { y: 1 }, X { y: 1 }.y
             contains_exterior_struct_lit(x)
         }