Check var scope if it exist

compiler/rustc_middle/src/middle/region.rs

@@ -362,12 +362,9 @@ impl ScopeTree {
         self.parent_map.get(&id).cloned().map(|(p, _)| p)
     }
 
-    /// Returns the lifetime of the local variable `var_id`
-    pub fn var_scope(&self, var_id: hir::ItemLocalId) -> Scope {
-        self.var_map
-            .get(&var_id)
-            .cloned()
-            .unwrap_or_else(|| bug!("no enclosing scope for id {:?}", var_id))
+    /// Returns the lifetime of the local variable `var_id`, if any.
+    pub fn var_scope(&self, var_id: hir::ItemLocalId) -> Option<Scope> {
+        self.var_map.get(&var_id).cloned()
     }
 
     /// Returns the scope when the temp created by `expr_id` will be cleaned up.

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -701,17 +701,19 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         let local_id = self.var_local_id(var, for_guard);
         let source_info = self.source_info(span);
         self.cfg.push(block, Statement { source_info, kind: StatementKind::StorageLive(local_id) });
-        let region_scope = self.region_scope_tree.var_scope(var.local_id);
-        if schedule_drop {
+        // Altough there is almost always scope for given variable in corner cases
+        // like #92893 we might get variable with no scope.
+        if let Some(region_scope) = self.region_scope_tree.var_scope(var.local_id) && schedule_drop{
             self.schedule_drop(span, region_scope, local_id, DropKind::Storage);
         }
         Place::from(local_id)
     }
 
     crate fn schedule_drop_for_binding(&mut self, var: HirId, span: Span, for_guard: ForGuard) {
         let local_id = self.var_local_id(var, for_guard);
-        let region_scope = self.region_scope_tree.var_scope(var.local_id);
-        self.schedule_drop(span, region_scope, local_id, DropKind::Value);
+        if let Some(region_scope) = self.region_scope_tree.var_scope(var.local_id) {
+            self.schedule_drop(span, region_scope, local_id, DropKind::Value);
+        }
     }
 
     /// Visit all of the primary bindings in a patterns, that is, visit the

compiler/rustc_typeck/src/check/generator_interior.rs

@@ -319,7 +319,7 @@ impl<'a, 'tcx> Visitor<'tcx> for InteriorVisitor<'a, 'tcx> {
         self.expr_count += 1;
 
         if let PatKind::Binding(..) = pat.kind {
-            let scope = self.region_scope_tree.var_scope(pat.hir_id.local_id);
+            let scope = self.region_scope_tree.var_scope(pat.hir_id.local_id).unwrap();
             let ty = self.fcx.typeck_results.borrow().pat_ty(pat);
             self.record(ty, pat.hir_id, Some(scope), None, pat.span, false);
         }

src/test/ui/mir/issue-92893.rs

@@ -0,0 +1,7 @@
+struct Bug<A = [(); (let a = (), 1).1]> {
+    //~^ `let` expressions are not supported here
+    //~^^ `let` expressions in this position are unstable [E0658]
+    a: A
+}
+
+fn main() {}

src/test/ui/mir/issue-92893.stderr

@@ -0,0 +1,20 @@
+error: `let` expressions are not supported here
+  --> $DIR/issue-92893.rs:1:22
+   |
+LL | struct Bug<A = [(); (let a = (), 1).1]> {
+   |                      ^^^^^^^^^^
+   |
+   = note: only supported directly in conditions of `if` and `while` expressions
+
+error[E0658]: `let` expressions in this position are unstable
+  --> $DIR/issue-92893.rs:1:22
+   |
+LL | struct Bug<A = [(); (let a = (), 1).1]> {
+   |                      ^^^^^^^^^^
+   |
+   = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
+   = help: add `#![feature(let_chains)]` to the crate attributes to enable
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0658`.

src/tools/clippy/clippy_lints/src/loops/needless_range_loop.rs

@@ -59,7 +59,7 @@ pub(super) fn check<'tcx>(
                 if let Some(indexed_extent) = indexed_extent {
                     let parent_def_id = cx.tcx.hir().get_parent_item(expr.hir_id);
                     let region_scope_tree = cx.tcx.region_scope_tree(parent_def_id);
-                    let pat_extent = region_scope_tree.var_scope(pat.hir_id.local_id);
+                    let pat_extent = region_scope_tree.var_scope(pat.hir_id.local_id).unwrap();
                     if region_scope_tree.is_subscope_of(indexed_extent, pat_extent) {
                         return;
                     }
@@ -262,7 +262,7 @@ impl<'a, 'tcx> VarVisitor<'a, 'tcx> {
                 match res {
                     Res::Local(hir_id) => {
                         let parent_def_id = self.cx.tcx.hir().get_parent_item(expr.hir_id);
-                        let extent = self.cx.tcx.region_scope_tree(parent_def_id).var_scope(hir_id.local_id);
+                        let extent = self.cx.tcx.region_scope_tree(parent_def_id).var_scope(hir_id.local_id).unwrap();
                         if index_used_directly {
                             self.indexed_directly.insert(
                                 seqvar.segments[0].ident.name,

src/tools/clippy/clippy_lints/src/shadow.rs

@@ -160,8 +160,8 @@ impl<'tcx> LateLintPass<'tcx> for Shadow {
 
 fn is_shadow(cx: &LateContext<'_>, owner: LocalDefId, first: ItemLocalId, second: ItemLocalId) -> bool {
     let scope_tree = cx.tcx.region_scope_tree(owner.to_def_id());
-    let first_scope = scope_tree.var_scope(first);
-    let second_scope = scope_tree.var_scope(second);
+    let first_scope = scope_tree.var_scope(first).unwrap();
+    let second_scope = scope_tree.var_scope(second).unwrap();
     scope_tree.is_subscope_of(second_scope, first_scope)
 }