[AddressLowering] Map-into-ctx type for yield.

Previously, the type for the storage into which a loadable value which
was yielded via an indirect convention was obtained from the
SILFunctionConventions and the SILYieldIfo but not mapped into the
context of the current function.  Here, that's fixed.

Author: nate-chandler

lib/SILOptimizer/Mandatory/AddressLowering.cpp

@@ -2815,8 +2815,8 @@ void YieldRewriter::rewriteYield(YieldInst *yieldInst) {
 void YieldRewriter::rewriteOperand(YieldInst *yieldInst, unsigned index) {
   auto info = opaqueFnConv.getYieldInfoForOperandIndex(index);
   auto convention = info.getConvention();
-  auto ty =
-      opaqueFnConv.getSILType(info, pass.function->getTypeExpansionContext());
+  auto ty = pass.function->mapTypeIntoContext(
+      opaqueFnConv.getSILType(info, pass.function->getTypeExpansionContext()));
   if (ty.isAddressOnly(*pass.function)) {
     assert(yieldInst->getOperand(index)->getType().isAddress() &&
            "rewriting yield of of address-only value after use rewriting!?");

test/SILOptimizer/address_lowering.sil

@@ -37,6 +37,10 @@ struct LoadableNontrivial {
     var x: Klass
 }
 
+struct LoadableNontrivialGeneric<T> {
+  var x: Klass
+}
+
 struct SI<T> {
   var element: T
   var index: I
@@ -2642,3 +2646,29 @@ unwindbb:
   abort_apply %token
   unwind
 }
+
+// Verify that the type of the alloc_stack is appropriately mapped into the
+// function's context.
+// CHECK-LABEL: sil [ossa] @test_yield_D_loadable_generic_as_inguaranteed : {{.*}} <T> {{.*}} {
+// CHECK:         ([[INSTANCE_ADDR:%[^,]+]], {{%[^,]+}}) = begin_apply undef<T>()
+// CHECK:         [[INSTANCE:%[^,]+]] = load_borrow [[INSTANCE_ADDR:%[^,]+]]
+// CHECK:         [[STACK_ADDR:%[^,]+]] = alloc_stack $LoadableNontrivialGeneric<T>  
+//                                                                              ^^^ Verify that T and not τ_0_0 appears
+// CHECK:         [[YIELDABLE_INSTANCE:%[^,]+]] = store_borrow [[INSTANCE:%[^,]+]] to [[STACK_ADDR:%[^,]+]]
+// CHECK:         yield [[YIELDABLE_INSTANCE]]
+// CHECK-LABEL: } // end sil function 'test_yield_D_loadable_generic_as_inguaranteed'
+sil [ossa] @test_yield_D_loadable_generic_as_inguaranteed : $@yield_once @convention(thin) <T> () -> @yields @in_guaranteed LoadableNontrivialGeneric<T> {
+bb0:
+  (%3, %4) = begin_apply undef<T>() : $@yield_once @convention(method) <Tee> () -> @yields @in_guaranteed LoadableNontrivialGeneric<Tee>
+  yield %3 : $LoadableNontrivialGeneric<T>, resume bb1, unwind bb2
+
+bb1:
+  end_apply %4
+  %7 = tuple ()
+  return %7 : $()
+
+bb2:
+  abort_apply %4
+  unwind
+}
+