IRGen: Fix isDependentConformance() to resolve type witnesses if necessary

Author: slavapestov

lib/IRGen/GenProto.cpp

@@ -854,7 +854,7 @@ static bool hasDependentTypeWitness(
     return false;
 
   // Check whether any of the associated types are dependent.
-  if (conformance->forEachTypeWitness(nullptr,
+  if (conformance->forEachTypeWitness(DC->getASTContext().getLazyResolver(),
         [&](AssociatedTypeDecl *requirement, Type type,
             TypeDecl *explicitDecl) -> bool {
           // Skip associated types that don't have witness table entries.

test/IRGen/Inputs/signature_conformances_other.swift

@@ -2,6 +2,10 @@ protocol Q {
   associatedtype T
 }
 
+struct AlsoConforms<T> : Q {}
+
+func takesQ<T : Q>(_: T) {}
+
 protocol P : Q {
   associatedtype U
 }

test/IRGen/signature_conformances_multifile.swift

@@ -3,6 +3,18 @@
 // Make sure we correctly determine the witness table is dependent, even though
 // it was defined in a different file.
 
+// CHECK-LABEL: define hidden swiftcc void @"$s32signature_conformances_multifile5passQyyF"()
+func passQ() {
+  // CHECK: call swiftcc void @"$s32signature_conformances_multifile12AlsoConformsVACyxGycfC"(%swift.type* @"$sSiN")
+  // CHECK: %0 = call swiftcc %swift.metadata_response @"$s32signature_conformances_multifile12AlsoConformsVySiGMa"
+  // CHECK: %1 = extractvalue %swift.metadata_response %0
+  // CHECK: %2 = call i8** @"$s32signature_conformances_multifile12AlsoConformsVySiGACyxGAA1QAAWl"()
+  // CHECK: call swiftcc void @"$s32signature_conformances_multifile6takesQyyxAA1QRzlF"(%swift.opaque* noalias nocapture undef, %swift.type* %1, i8** %2)
+  takesQ(AlsoConforms<Int>())
+
+  // CHECK: ret void
+}
+
 // CHECK-LABEL: define hidden swiftcc void @"$s32signature_conformances_multifile5passPyyF"()
 func passP() {
   // CHECK: call swiftcc void @"$s32signature_conformances_multifile8ConformsVACyxq_GycfC"(%swift.type* @"$sSiN", %swift.type* @"$sSSN")