Merge pull request swiftlang#33624 from slavapestov/ast-scope-crash-with-pattern-binding-init-function-builder

AST: Fix ASTScopeLookup crash if a PatternBindingEntry's context is not a PatternBindingInitializer

Author: slavapestov

lib/AST/ASTScopeLookup.cpp

@@ -519,7 +519,7 @@ bool BraceStmtScope::lookupLocalsOrMembers(ArrayRef<const ASTScopeImpl *>,
 bool PatternEntryInitializerScope::lookupLocalsOrMembers(
     ArrayRef<const ASTScopeImpl *>, DeclConsumer consumer) const {
   // 'self' is available within the pattern initializer of a 'lazy' variable.
-  auto *initContext = cast_or_null<PatternBindingInitializer>(
+  auto *initContext = dyn_cast_or_null<PatternBindingInitializer>(
       decl->getInitContext(0));
   if (initContext) {
     if (auto *selfParam = initContext->getImplicitSelfDecl()) {
@@ -816,7 +816,7 @@ Optional<bool> ClosureBodyScope::resolveIsCascadingUseForThisScope(
 Optional<bool> PatternEntryInitializerScope::resolveIsCascadingUseForThisScope(
     Optional<bool> isCascadingUse) const {
   auto *const initContext = getPatternEntry().getInitContext();
-  auto *PBI = cast_or_null<PatternBindingInitializer>(initContext);
+  auto *PBI = dyn_cast_or_null<PatternBindingInitializer>(initContext);
   auto *isd = PBI ? PBI->getImplicitSelfDecl() : nullptr;
 
   // 'self' is available within the pattern initializer of a 'lazy' variable.

validation-test/compiler_crashers_2_fixed/rdar67239650.swift

@@ -0,0 +1,24 @@
+// RUN: %target-swift-frontend -typecheck %s
+
+@_functionBuilder
+struct SillyBuilder {
+  static func buildBlock() -> () {}
+}
+
+struct SillyStruct {
+  init(@SillyBuilder _: () -> ()) {}
+}
+
+struct UsesSillyStruct {
+  var x: Int = 0
+
+  func foo() {
+    SillyStruct {
+      let fn = {
+        if true {
+          _ = x
+        }
+      }
+    }
+  }
+}