Sema: Check AnyObject requirements of variadic generic functions

Author: slavapestov

lib/Sema/CSSimplify.cpp

@@ -3659,6 +3659,19 @@ ConstraintSystem::matchExistentialTypes(Type type1, Type type2,
     return getTypeMatchFailure(locator);
   }
 
+  // ConformsTo constraints are generated when opening a generic
+  // signature with a RequirementKind::Conformance requirement, so
+  // we must handle pack types on the left by splitting up into
+  // smaller constraints.
+  if (auto *packType = type1->getAs<PackType>()) {
+    for (unsigned i = 0, e = packType->getNumElements(); i < e; ++i) {
+      addConstraint(kind, packType->getElementType(i), type2,
+                    locator.withPathElement(LocatorPathElt::PackElement(i)));
+    }
+
+    return getTypeMatchSuccess();
+  }
+
   TypeMatchOptions subflags = getDefaultDecompositionOptions(flags);
 
   // Handle existential metatypes.
@@ -3675,6 +3688,8 @@ ConstraintSystem::matchExistentialTypes(Type type1, Type type2,
                                    locator.withPathElement(
                                      ConstraintLocator::InstanceType));
     }
+
+    return getTypeMatchSuccess();
   }
 
   if (!type2->isExistentialType())
@@ -7522,7 +7537,6 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyConformsToConstraint(
     return SolutionKind::Solved;
   }
 
-
   auto *loc = getConstraintLocator(locator);
 
   /// Record the given conformance as the result, adding any conditional

test/Constraints/variadic_generic_constraints.swift

@@ -3,6 +3,8 @@
 // Test instantiation of constraint solver constraints from generic requirements
 // involving type pack parameters
 
+// Conformance requirements
+
 protocol P {}
 
 func takesP<T...: P>(_: T...) {}  // expected-note {{where 'T' = 'DoesNotConformToP'}}
@@ -13,9 +15,10 @@ struct DoesNotConformToP {}
 takesP()  // ok
 takesP(ConformsToP(), ConformsToP(), ConformsToP())  // ok
 
-// FIXME: Bad diagnostic
 takesP(ConformsToP(), DoesNotConformToP(), ConformsToP()) // expected-error {{global function 'takesP' requires that 'DoesNotConformToP' conform to 'P'}}
 
+// Superclass requirements
+
 class C {}
 
 class SubclassOfC: C {}
@@ -28,6 +31,20 @@ takesC(SubclassOfC(), SubclassOfC(), SubclassOfC())  // ok
 
 takesC(SubclassOfC(), NotSubclassOfC(), SubclassOfC())  // expected-error {{global function 'takesC' requires that 'NotSubclassOfC' inherit from 'C'}}
 
+// Layout requirements
+
+struct S {}
+
+func takesAnyObject<T...: AnyObject>(_: T...) {}
+
+takesAnyObject()
+takesAnyObject(C(), C(), C())
+
+// FIXME: Bad diagnostic
+takesAnyObject(C(), S(), C())  // expected-error {{type of expression is ambiguous without more context}}
+
+// Same-type requirements
+
 func takesParallelSequences<T..., U...>(t: T..., u: U...) where T: Sequence, U: Sequence, T.Element == U.Element {}
 // expected-note@-1 {{where 'T.Element' = 'String', 'U.Element' = 'Int'}}