Merge pull request #39096 from xedin/rdar-80271666-take-2

[ConstraintSystem] Allow IUO types to be unrelated while forming a di…

Author: xedin

include/swift/Sema/ConstraintSystem.h

@@ -4524,8 +4524,25 @@ class ConstraintSystem {
     Type underlyingType;
     if (auto *fnTy = type->getAs<AnyFunctionType>())
       underlyingType = replaceFinalResultTypeWithUnderlying(fnTy);
-    else
+    else if (auto *typeVar =
+                 type->getWithoutSpecifierType()->getAs<TypeVariableType>()) {
+      auto *locator = typeVar->getImpl().getLocator();
+
+      // If `type` hasn't been resolved yet, we need to allocate a type
+      // variable to represent an object type of a future optional, and
+      // add a constraint beetween `type` and `underlyingType` to model it.
+      underlyingType = createTypeVariable(
+          getConstraintLocator(locator, LocatorPathElt::GenericArgument(0)),
+          TVO_PrefersSubtypeBinding | TVO_CanBindToLValue |
+              TVO_CanBindToNoEscape);
+
+      // Using a `typeVar` here because l-value is going to be applied
+      // to the underlying type below.
+      addConstraint(ConstraintKind::OptionalObject, typeVar, underlyingType,
+                    locator);
+    } else {
       underlyingType = type->getWithoutSpecifierType()->getOptionalObjectType();
+    }
 
     assert(underlyingType);
 

validation-test/Sema/type_checker_crashers_fixed/sr14893.swift

@@ -0,0 +1,29 @@
+// RUN: %target-typecheck-verify-swift -target %target-cpu-apple-macosx10.15 -swift-version 5
+
+// REQUIRES: OS=macosx
+
+enum Category {
+case first
+}
+
+protocol View {}
+
+extension View {
+  func test(_ tag: Category) -> some View {
+    Image()
+  }
+}
+
+@resultBuilder struct ViewBuilder {
+  static func buildBlock<Content>(_ content: Content) -> Content where Content : View { fatalError() }
+}
+
+struct Image : View {
+}
+
+struct MyView {
+  @ViewBuilder var body: some View {
+    let icon: Category! = Category.first // expected-error {{using '!' is not allowed here; perhaps '?' was intended?}} {{23-24=?}}
+    Image().test(icon)
+  }
+}