[Sema] Allow optional hole propagation in code completion mode

Author: LucianoPAlmeida

lib/Sema/CSBindings.cpp

@@ -1993,11 +1993,16 @@ bool TypeVariableBinding::attempt(ConstraintSystem &cs) const {
   // without any contextual information, so even though `x` would get
   // bound to result type of the chain, underlying type variable wouldn't
   // be resolved, so we need to propagate holes up the conversion chain.
-  if (TypeVar->getImpl().canBindToHole() &&
-      srcLocator->directlyAt<OptionalEvaluationExpr>()) {
-    if (auto objectTy = type->getOptionalObjectType()) {
-      if (auto *typeVar = objectTy->getAs<TypeVariableType>())
-        cs.recordPotentialHole(typeVar);
+  // Also propagate in code completion mode because in some cases code
+  // completion relies on type variable being a potential hole.
+  if (TypeVar->getImpl().canBindToHole()) {
+    if (srcLocator->directlyAt<OptionalEvaluationExpr>() ||
+        cs.isForCodeCompletion()) {
+      if (auto objectTy = type->getOptionalObjectType()) {
+        if (auto *typeVar = objectTy->getAs<TypeVariableType>()) {
+          cs.recordPotentialHole(typeVar);
+        }
+      }
     }
   }
 

validation-test/IDE/stress_tester_issues_fixed/rdar93127707.swift

@@ -0,0 +1,9 @@
+// RUN: %swift-ide-test -code-completion -source-filename %s -code-completion-token COMPLETE | %FileCheck %s
+
+struct Foo {
+  var x: Int = {
+    guard let foo = #^COMPLETE^#
+  }()
+}
+
+// CHECK: Decl[Struct]/CurrModule:            Foo[#Foo#];