Runtime: Fix dynamic casts of variadic types that conditionally conform

Author: slavapestov

stdlib/public/runtime/MetadataLookup.cpp

@@ -2850,16 +2850,20 @@ void SubstGenericParametersFromMetadata::setup() const {
     assert(baseContext);
     DemanglerForRuntimeTypeResolution<StackAllocatedDemangler<2048>> demangler;
     numKeyGenericParameters = buildDescriptorPath(baseContext, demangler);
+    if (auto *genericCtx = baseContext->getGenericContext())
+      numShapeClasses = genericCtx->getGenericPackShapeHeader().NumShapeClasses;
     return;
   }
   case SourceKind::Environment: {
     assert(environment);
     numKeyGenericParameters = buildEnvironmentPath(environment);
+    // FIXME: Variadic generics
     return;
   }
   case SourceKind::Shape: {
     assert(shape);
     numKeyGenericParameters = buildShapePath(shape);
+    // FIXME: Variadic generics
     return;
   }
   }
@@ -2883,7 +2887,7 @@ SubstGenericParametersFromMetadata::getMetadata(
     return MetadataOrPack();
 
   // Compute the flat index.
-  unsigned flatIndex = pathElement.numKeyGenericParamsInParent;
+  unsigned flatIndex = pathElement.numKeyGenericParamsInParent + numShapeClasses;
   if (pathElement.hasNonKeyGenericParams > 0) {
     // We have non-key generic parameters at this level, so the index needs to
     // be checked more carefully.
@@ -2912,7 +2916,8 @@ SubstGenericParametersFromMetadata::getWitnessTable(const Metadata *type,
   // On first access, compute the descriptor path.
   setup();
 
-  return (const WitnessTable *)genericArgs[index + numKeyGenericParameters];
+  return (const WitnessTable *)genericArgs[
+      index + numKeyGenericParameters + numShapeClasses];
 }
 
 MetadataOrPack SubstGenericParametersFromWrittenArgs::getMetadata(

stdlib/public/runtime/Private.h

@@ -395,6 +395,9 @@ class TypeInfo {
     /// The number of key generic parameters.
     mutable unsigned numKeyGenericParameters = 0;
 
+    /// The number of pack shape classes.
+    mutable unsigned numShapeClasses = 0;
+
     /// Builds the descriptor path.
     ///
     /// \returns a pair containing the number of key generic parameters in

stdlib/public/runtime/ProtocolConformance.cpp

@@ -332,8 +332,7 @@ ProtocolConformanceDescriptor::getWitnessTable(const Metadata *type) const {
     auto error = _checkGenericRequirements(
         getConditionalRequirements(), conditionalArgs,
         [&substitutions](unsigned depth, unsigned index) {
-          // FIXME: Variadic generics
-          return substitutions.getMetadata(depth, index).getMetadataOrNull();
+          return substitutions.getMetadata(depth, index).Ptr;
         },
         [&substitutions](const Metadata *type, unsigned index) {
           return substitutions.getWitnessTable(type, index);

test/Interpreter/variadic_generic_conditional_conformances.swift

@@ -45,4 +45,18 @@ conformances.test("conditional") {
   expectEqual(["Int", "String"], callFoobar(G<Int, String>()))
 }
 
+func cast<T, U>(_ value: T, to: U.Type) -> Bool {
+  return value is U
+}
+
+conformances.test("cast") {
+  expectEqual(true, cast(G< >(), to: (any P).self))
+  expectEqual(true, cast(G<Int>(), to: (any P).self))
+  expectEqual(true, cast(G<Int, String>(), to: (any P).self))
+
+  expectEqual(false, cast(G<Bool>(), to: (any P).self))
+  expectEqual(false, cast(G<Int, Bool>(), to: (any P).self))
+  expectEqual(false, cast(G<Bool, Int>(), to: (any P).self))
+}
+
 runAllTests()