[5.8][CSGen] Handle recursive use of variable declarations

lib/Sema/CSGen.cpp

@@ -1351,20 +1351,33 @@ namespace {
     Type visitDeclRefExpr(DeclRefExpr *E) {
       auto locator = CS.getConstraintLocator(E);
 
+      auto invalidateReference = [&]() -> Type {
+        auto *hole = CS.createTypeVariable(locator, TVO_CanBindToHole);
+        (void)CS.recordFix(AllowRefToInvalidDecl::create(CS, locator));
+        CS.setType(E, hole);
+        return hole;
+      };
+
       Type knownType;
       if (auto *VD = dyn_cast<VarDecl>(E->getDecl())) {
         knownType = CS.getTypeIfAvailable(VD);
         if (!knownType)
           knownType = CS.getVarType(VD);
 
         if (knownType) {
+          // An out-of-scope type variable could be a type of a declaration
+          // only in diagnostic mode when invalid variable declaration is
+          // recursively referenced inside of a multi-statement closure
+          // located somewhere within its initializer e.g.:
+          // `let x = [<call>] { ... print(x) }`
+          if (auto *typeVar = knownType->getAs<TypeVariableType>()) {
+            if (!CS.isActiveTypeVariable(typeVar))
+              return invalidateReference();
+          }
+
           // If the known type has an error, bail out.
           if (knownType->hasError()) {
-            auto *hole = CS.createTypeVariable(locator, TVO_CanBindToHole);
-            (void)CS.recordFix(AllowRefToInvalidDecl::create(CS, locator));
-            if (!CS.hasType(E))
-              CS.setType(E, hole);
-            return hole;
+            return invalidateReference();
           }
 
           if (!knownType->hasPlaceholder()) {
@@ -1381,10 +1394,7 @@ namespace {
       // (in getTypeOfReference) so we can match non-error param types.
       if (!knownType && E->getDecl()->isInvalid() &&
           !CS.isForCodeCompletion()) {
-        auto *hole = CS.createTypeVariable(locator, TVO_CanBindToHole);
-        (void)CS.recordFix(AllowRefToInvalidDecl::create(CS, locator));
-        CS.setType(E, hole);
-        return hole;
+        return invalidateReference();
       }
 
       // Create an overload choice referencing this declaration and immediately

lib/Sema/CSSyntacticElement.cpp

@@ -74,7 +74,7 @@ class TypeVariableRefFinder : public ASTWalker {
     if (auto *DRE = dyn_cast<DeclRefExpr>(expr)) {
       auto *decl = DRE->getDecl();
 
-      if (auto type = CS.getTypeIfAvailable(DRE->getDecl())) {
+      if (auto type = CS.getTypeIfAvailable(decl)) {
         auto &ctx = CS.getASTContext();
         // If this is not one of the closure parameters which
         // is inferrable from the body, let's replace type

test/expr/closure/multi_statement.swift

@@ -650,3 +650,16 @@ func test_that_closures_are_attempted_in_order() {
     return false
   }
 }
+
+// https://github.com/apple/swift/issues/63455
+func test_recursive_var_reference_in_multistatement_closure() {
+  func takeClosure(_ x: () -> Void) {}
+
+  func test(optionalInt: Int?) {
+    takeClosure {
+      let int = optionalInt { // expected-error {{cannot call value of non-function type 'Int?'}}
+        print(int)
+      }
+    }
+  }
+}

validation-test/IDE/crashers_2_fixed/issue-63455.swift

@@ -0,0 +1,25 @@
+// RUN: %swift-ide-test -code-completion -source-filename %s -code-completion-token COMPLETE
+
+func sheet(onDismiss: () -> Void) -> EmptyView {
+  fatalError()
+}
+
+@resultBuilder struct ViewBuilder2 {
+  static func buildBlock(_ content: EmptyView) -> EmptyView {
+    return content
+  }
+}
+
+struct EmptyView {}
+
+struct SettingsView {
+  var importedFile: Int?
+
+  @ViewBuilder2 var body2: EmptyView {
+    sheet {
+      #^COMPLETE^#if let url = self.importedFile {
+        print(url)
+      }
+    }
+  }
+}