[SILGen] InitAccessors: Lower initializes/accesses property types before using them in init accessor type

(cherry picked from commit eeb70cf)

Author: xedin

lib/SIL/IR/SILFunctionType.cpp

@@ -2381,22 +2381,27 @@ static CanSILFunctionType getSILFunctionTypeForInitAccessor(
   // Drop `self` parameter.
   inputs.pop_back();
 
+  auto getLoweredTypeOfProperty = [&](VarDecl *property) {
+    auto type = property->getInterfaceType();
+    AbstractionPattern pattern(genericSig, type->getCanonicalType());
+    auto loweredTy = TC.getLoweredType(pattern, type, context);
+    return loweredTy.getASTType();
+  };
+
   // accessed properties appear as `inout` parameters because they could be
   // read from and modified.
   for (auto *property : accessor->getAccessedProperties()) {
-    inputs.push_back(
-        SILParameterInfo(property->getInterfaceType()->getCanonicalType(),
-                         ParameterConvention::Indirect_Inout));
+    inputs.push_back(SILParameterInfo(getLoweredTypeOfProperty(property),
+                                      ParameterConvention::Indirect_Inout));
   }
 
   SmallVector<SILResultInfo, 8> results;
 
   // initialized properties appear as `@out` results because they are
   // initialized by the accessor.
   for (auto *property : accessor->getInitializedProperties()) {
-    results.push_back(
-        SILResultInfo(property->getInterfaceType()->getCanonicalType(),
-                      ResultConvention::Indirect));
+    results.push_back(SILResultInfo(getLoweredTypeOfProperty(property),
+                                    ResultConvention::Indirect));
   }
 
   auto calleeConvention = ParameterConvention::Direct_Unowned;

lib/SILGen/SILGenConstructor.cpp

@@ -1584,8 +1584,8 @@ void SILGenFunction::emitInitAccessor(AccessorDecl *accessor) {
                             bool markUninitialized = false) {
     auto *arg = ParamDecl::createImplicit(
         getASTContext(), property->getBaseIdentifier(),
-        property->getBaseIdentifier(), type.getASTType()->mapTypeOutOfContext(),
-        accessor, ParamSpecifier::InOut);
+        property->getBaseIdentifier(), property->getInterfaceType(), accessor,
+        ParamSpecifier::InOut);
 
     RegularLocation loc(property);
     loc.markAutoGenerated();

test/SILOptimizer/init_accessors.swift

@@ -395,6 +395,30 @@ func test_local_with_memberwise() {
   _ = TestMemberwiseGeneric(a: 1, pair: ("a", [0]))
 }
 
+// CHECK-LABEL: sil private [ossa] @$s14init_accessors023test_type_lowering_for_A9_accessoryyF4TestL_V2fnADyxq_Gq_xc_tcfC : $@convention(method) <T, U> (@owned @callee_guaranteed @substituted <τ_0_0, τ_0_1> (@in_guaranteed τ_0_0) -> @out τ_0_1 for <T, U>, @thin Test<T, U>.Type) -> @owned Test<T, U>
+// CHECK: {{.*}} = function_ref @$s14init_accessors023test_type_lowering_for_A9_accessoryyF4TestL_V2fnyq_xcvi : $@convention(thin) <τ_0_0, τ_0_1> (@owned @callee_guaranteed @substituted <τ_0_0, τ_0_1> (@in_guaranteed τ_0_0) -> @out τ_0_1 for <τ_0_0, τ_0_1>) -> @out Optional<@callee_guaranteed @substituted <τ_0_0, τ_0_1> (@in_guaranteed τ_0_0) -> @out τ_0_1 for <τ_0_0, τ_0_1>>
+func test_type_lowering_for_init_accessor() {
+  struct Test<T, U> {
+    var _fn: ((T) -> U)? = nil
+
+    // CHECK-LABEL: sil private [ossa] @$s14init_accessors023test_type_lowering_for_A9_accessoryyF4TestL_V2fnyq_xcvi : $@convention(thin) <T, U> (@owned @callee_guaranteed @substituted <τ_0_0, τ_0_1> (@in_guaranteed τ_0_0) -> @out τ_0_1 for <T, U>) -> @out Optional<@callee_guaranteed @substituted <τ_0_0, τ_0_1> (@in_guaranteed τ_0_0) -> @out τ_0_1 for <T, U>>
+    var fn: (T) -> U {
+      @storageRestrictions(initializes: _fn)
+      init { _fn = newValue }
+      get { _fn! }
+      set { _fn = newValue }
+    }
+
+    init(fn: @escaping (T) -> U) {
+      self.fn = fn
+    }
+  }
+
+  _ = Test<Int, () -> Void> { _ in
+    return {}
+  } // Ok
+}
+
 func test_assignments() {
   struct Test {
     var _a: Int