Grammar: Don't allow inner attrs in certain block expressions

src/expressions/block-expr.md

@@ -9,6 +9,11 @@ BlockExpression ->
         Statements?
     `}`
 
+BlockExpressionNoInnerAttributes ->
+    `{`
+        Statements?
+    `}`
+
 Statements ->
       Statement+
     | Statement+ ExpressionWithoutBlock

src/expressions/if-expr.md

@@ -4,8 +4,8 @@ r[expr.if]
 r[expr.if.syntax]
 ```grammar,expressions
 IfExpression ->
-    `if` Conditions BlockExpression
-    (`else` ( BlockExpression | IfExpression ) )?
+    `if` Conditions BlockExpressionNoInnerAttributes
+    (`else` ( BlockExpressionNoInnerAttributes | IfExpression ) )?
 
 Conditions ->
       Expression _except [StructExpression]_

src/macros-by-example.md

@@ -106,7 +106,7 @@ In the matcher, `$` _name_ `:` _fragment-specifier_ matches a Rust syntax fragme
 r[macro.decl.meta.specifier]
 Valid fragment specifiers are:
 
-  * `block`: a [BlockExpression]
+  * `block`: a [BlockExpressionNoInnerAttributes]
   * `expr`: an [Expression]
   * `expr_2021`: an [Expression] except [UnderscoreExpression] and [ConstBlockExpression] (see [macro.decl.meta.edition2024])
   * `ident`: an [IDENTIFIER_OR_KEYWORD] except `_`, [RAW_IDENTIFIER], or [`$crate`]

src/statements.md

@@ -58,7 +58,8 @@ LetStatement ->
     OuterAttribute* `let` PatternNoTopAlt ( `:` Type )?
     (
           `=` Expression
-        | `=` Expression _except [LazyBooleanExpression] or end with a `}`_ `else` BlockExpression
+        | `=` Expression _except [LazyBooleanExpression] or end with a `}`_
+              `else` BlockExpressionNoInnerAttributes
     )? `;`
 ```