Rollup merge of #132653 - BoxyUwU:const_arg_stmt_mac_call, r=compiler-errors

Don't use `maybe_unwrap_block` when checking for macro calls in a block expr

Fixes #131915

Using `maybe_unwrap_block` to determine if we are looking at a `{ mac_call!{} }` will fail sometimes as `mac_call!{}` could be a `StmtKind::MacCall` not a `StmtKind::Expr`. This caused the def collector to think that `{ mac_call!{} }` was a non-trivial const argument and create a definition for it even though it should not.

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

2 files changed, 41 insertions, 23 deletions

diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
index 997c44cffff..5f71fb97d76 100644
--- a/compiler/rustc_ast/src/ast.rs
+++ b/compiler/rustc_ast/src/ast.rs
@@ -1194,7 +1194,7 @@ impl Expr {
     ///
     /// Does not ensure that the path resolves to a const param, the caller should check this.
     pub fn is_potential_trivial_const_arg(&self, strip_identity_block: bool) -> bool {
-        let this = if strip_identity_block { self.maybe_unwrap_block().1 } else { self };
+        let this = if strip_identity_block { self.maybe_unwrap_block() } else { self };
 
         if let ExprKind::Path(None, path) = &this.kind
             && path.is_potential_trivial_const_arg()
@@ -1206,14 +1206,41 @@ impl Expr {
     }
 
     /// Returns an expression with (when possible) *one* outter brace removed
-    pub fn maybe_unwrap_block(&self) -> (bool, &Expr) {
+    pub fn maybe_unwrap_block(&self) -> &Expr {
         if let ExprKind::Block(block, None) = &self.kind
             && let [stmt] = block.stmts.as_slice()
             && let StmtKind::Expr(expr) = &stmt.kind
         {
-            (true, expr)
+            expr
         } else {
-            (false, self)
+            self
+        }
+    }
+
+    /// Determines whether this expression is a macro call optionally wrapped in braces . If
+    /// `already_stripped_block` is set then we do not attempt to peel off a layer of braces.
+    ///
+    /// Returns the [`NodeId`] of the macro call and whether a layer of braces has been peeled
+    /// either before, or part of, this function.
+    pub fn optionally_braced_mac_call(
+        &self,
+        already_stripped_block: bool,
+    ) -> Option<(bool, NodeId)> {
+        match &self.kind {
+            ExprKind::Block(block, None)
+                if let [stmt] = &*block.stmts
+                    && !already_stripped_block =>
+            {
+                match &stmt.kind {
+                    StmtKind::MacCall(_) => Some((true, stmt.id)),
+                    StmtKind::Expr(expr) if let ExprKind::MacCall(_) = &expr.kind => {
+                        Some((true, expr.id))
+                    }
+                    _ => None,
+                }
+            }
+            ExprKind::MacCall(_) => Some((already_stripped_block, self.id)),
+            _ => None,
         }
     }
 
diff --git a/compiler/rustc_resolve/src/def_collector.rs b/compiler/rustc_resolve/src/def_collector.rs
index a825458dc89..bf27b767a49 100644
--- a/compiler/rustc_resolve/src/def_collector.rs
+++ b/compiler/rustc_resolve/src/def_collector.rs
@@ -130,18 +130,16 @@ impl<'a, 'ra, 'tcx> DefCollector<'a, 'ra, 'tcx> {
         &self,
         anon_const: &'a AnonConst,
     ) -> Option<(PendingAnonConstInfo, NodeId)> {
-        let (block_was_stripped, expr) = anon_const.value.maybe_unwrap_block();
-        match expr {
-            Expr { kind: ExprKind::MacCall(..), id, .. } => Some((
+        anon_const.value.optionally_braced_mac_call(false).map(|(block_was_stripped, id)| {
+            (
                 PendingAnonConstInfo {
                     id: anon_const.id,
                     span: anon_const.value.span,
                     block_was_stripped,
                 },
-                *id,
-            )),
-            _ => None,
-        }
+                id,
+            )
+        })
     }
 
     /// Determines whether the expression `const_arg_sub_expr` is a simple macro call, sometimes
@@ -161,18 +159,11 @@ impl<'a, 'ra, 'tcx> DefCollector<'a, 'ra, 'tcx> {
             panic!("Checking expr is trivial macro call without having entered anon const: `{const_arg_sub_expr:?}`"),
         );
 
-        let (block_was_stripped, expr) = if pending_anon.block_was_stripped {
-            (true, const_arg_sub_expr)
-        } else {
-            const_arg_sub_expr.maybe_unwrap_block()
-        };
-
-        match expr {
-            Expr { kind: ExprKind::MacCall(..), id, .. } => {
-                Some((PendingAnonConstInfo { block_was_stripped, ..pending_anon }, *id))
-            }
-            _ => None,
-        }
+        const_arg_sub_expr.optionally_braced_mac_call(pending_anon.block_was_stripped).map(
+            |(block_was_stripped, id)| {
+                (PendingAnonConstInfo { block_was_stripped, ..pending_anon }, id)
+            },
+        )
     }
 }