Suggest wrapping mac args in parens rather than the whole expression

compiler/rustc_parse/messages.ftl

@@ -722,6 +722,8 @@ parse_sugg_turbofish_syntax = use `::<...>` instead of `<...>` to specify lifeti
 
 parse_sugg_wrap_expression_in_parentheses = wrap the expression in parentheses
 
+parse_sugg_wrap_macro_in_parentheses = use parentheses instead of braces for this macro
+
 parse_sugg_wrap_pattern_in_parens = wrap the pattern in parentheses
 
 parse_switch_mut_let_order =

compiler/rustc_parse/src/errors.rs

@@ -722,19 +722,32 @@ pub(crate) struct LabeledLoopInBreak {
     #[primary_span]
     pub span: Span,
     #[subdiagnostic]
-    pub sub: WrapExpressionInParentheses,
+    pub sub: WrapInParentheses,
 }
 
 #[derive(Subdiagnostic)]
+
+pub(crate) enum WrapInParentheses {
     #[multipart_suggestion(
         parse_sugg_wrap_expression_in_parentheses,
         applicability = "machine-applicable"
     )]
-pub(crate) struct WrapExpressionInParentheses {
+    Expression {
         #[suggestion_part(code = "(")]
-    pub left: Span,
+        left: Span,
         #[suggestion_part(code = ")")]
-    pub right: Span,
+        right: Span,
+    },
+    #[multipart_suggestion(
+        parse_sugg_wrap_macro_in_parentheses,
+        applicability = "machine-applicable"
+    )]
+    MacroArgs {
+        #[suggestion_part(code = "(")]
+        left: Span,
+        #[suggestion_part(code = ")")]
+        right: Span,
+    },
 }
 
 #[derive(Diagnostic)]
@@ -936,7 +949,7 @@ pub(crate) struct InvalidExpressionInLetElse {
     pub span: Span,
     pub operator: &'static str,
     #[subdiagnostic]
-    pub sugg: WrapExpressionInParentheses,
+    pub sugg: WrapInParentheses,
 }
 
 #[derive(Diagnostic)]
@@ -945,7 +958,7 @@ pub(crate) struct InvalidCurlyInLetElse {
     #[primary_span]
     pub span: Span,
     #[subdiagnostic]
-    pub sugg: WrapExpressionInParentheses,
+    pub sugg: WrapInParentheses,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_parse/src/parser/expr.rs

@@ -1844,7 +1844,7 @@ fn parse_expr_break(&mut self) -> PResult<'a, P<Expr>> {
             let lexpr = self.parse_expr_labeled(label, true)?;
             self.dcx().emit_err(errors::LabeledLoopInBreak {
                 span: lexpr.span,
-                sub: errors::WrapExpressionInParentheses {
+                sub: errors::WrapInParentheses::Expression {
                     left: lexpr.span.shrink_to_lo(),
                     right: lexpr.span.shrink_to_hi(),
                 },

compiler/rustc_parse/src/parser/stmt.rs

@@ -389,7 +389,7 @@ fn check_let_else_init_bool_expr(&self, init: &ast::Expr) {
                 self.dcx().emit_err(errors::InvalidExpressionInLetElse {
                     span: init.span,
                     operator: op.node.as_str(),
-                    sugg: errors::WrapExpressionInParentheses {
+                    sugg: errors::WrapInParentheses::Expression {
                         left: init.span.shrink_to_lo(),
                         right: init.span.shrink_to_hi(),
                     },
@@ -400,12 +400,19 @@ fn check_let_else_init_bool_expr(&self, init: &ast::Expr) {
 
     fn check_let_else_init_trailing_brace(&self, init: &ast::Expr) {
         if let Some(trailing) = classify::expr_trailing_brace(init) {
-            self.dcx().emit_err(errors::InvalidCurlyInLetElse {
+            let sugg = match &trailing.kind {
-                span: trailing.span.with_lo(trailing.span.hi() - BytePos(1)),
+                ExprKind::MacCall(mac) => errors::WrapInParentheses::MacroArgs {
-                sugg: errors::WrapExpressionInParentheses {
+                    left: mac.args.dspan.open,
+                    right: mac.args.dspan.close,
+                },
+                _ => errors::WrapInParentheses::Expression {
                     left: trailing.span.shrink_to_lo(),
                     right: trailing.span.shrink_to_hi(),
                 },
+            };
+            self.dcx().emit_err(errors::InvalidCurlyInLetElse {
+                span: trailing.span.with_lo(trailing.span.hi() - BytePos(1)),
+                sugg,
             });
         }
     }

tests/ui/parser/bad-let-else-statement.stderr

@@ -234,10 +234,10 @@ error: right curly brace `}` before `else` in a `let...else` statement not allow
 LL |     let bad = format_args! {""} else { return; };
    |                               ^
    |
-help: wrap the expression in parentheses
+help: use parentheses instead of braces for this macro
    |
-LL |     let bad = (format_args! {""}) else { return; };
+LL |     let bad = format_args! ("") else { return; };
-   |               +                 +
+   |                            ~  ~
 
 error: right curly brace `}` before `else` in a `let...else` statement not allowed
   --> $DIR/bad-let-else-statement.rs:181:25
@@ -249,10 +249,10 @@ LL |     b!(1); b!(2);
    |            ----- in this macro invocation
    |
    = note: this error originates in the macro `b` (in Nightly builds, run with -Z macro-backtrace for more info)
-help: wrap the expression in parentheses
+help: use parentheses instead of braces for this macro
    |
-LL |             let x = (a! {}) else { return; };
+LL |             let x = a! () else { return; };
-   |                     +     +
+   |                        ~~
 
 error: aborting due to 19 previous errors