[CoroutineAccessors] Default impls are transparent

Like every other method entry in the default witness table, the default
implementations of the `read2` and `modify2` accessors that just call
`read` and `modify` respectively should be transparent.

Author: nate-chandler

lib/Sema/TypeCheckStorage.cpp

@@ -2828,6 +2828,11 @@ IsAccessorTransparentRequest::evaluate(Evaluator &evaluator,
   if (accessor->getAttrs().hasAttribute<TransparentAttr>())
     return true;
 
+  // Default implementations of read2 and modify2 provided for back-deployment
+  // are transparent.
+  if (accessor->isRequirementWithSynthesizedDefaultImplementation())
+    return true;
+
   if (!accessor->isImplicit())
     return false;
 

test/SILGen/coroutine_accessors_skip.swift

@@ -0,0 +1,33 @@
+// RUN: %target-swift-emit-silgen                            \
+// RUN:     %s                                               \
+// RUN:     -experimental-skip-non-inlinable-function-bodies \
+// RUN:     -enable-library-evolution                        \
+// RUN:     -enable-experimental-feature CoroutineAccessors  \
+// RUN: | %FileCheck %s --check-prefixes=CHECK,CHECK-NOUNWIND
+
+// RUN: %target-swift-emit-silgen                                              \
+// RUN:     %s                                                                 \
+// RUN:     -experimental-skip-non-inlinable-function-bodies                   \
+// RUN:     -enable-library-evolution                                          \
+// RUN:     -enable-experimental-feature CoroutineAccessors                    \
+// RUN:     -enable-experimental-feature CoroutineAccessorsUnwindOnCallerError \
+// RUN: | %FileCheck %s --check-prefixes=CHECK,CHECK-UNWIND
+
+// REQUIRES: swift_feature_CoroutineAccessors
+// REQUIRES: swift_feature_CoroutineAccessorsUnwindOnCallerError
+
+// CHECK-LABEL: sil_default_witness_table MutatableAssociatedField {
+// CHECK-NEXT:    no_default
+// CHECK-NEXT:    no_default
+// CHECK-NEXT:    method #MutatableAssociatedField.field!read2
+// CHECK-SAME:        : @$s24coroutine_accessors_skip24MutatableAssociatedFieldP5field5AssocQzvy
+// CHECK-NEXT:    no_default
+// CHECK-NEXT:    no_default
+// CHECK-NEXT:    method #MutatableAssociatedField.field!modify2
+// CHECK-SAME:        : @$s24coroutine_accessors_skip24MutatableAssociatedFieldP5field5AssocQzvx
+// CHECK-NEXT:  }
+public protocol MutatableAssociatedField {
+  associatedtype Assoc
+
+  var field: Assoc { read set }
+}

test/SILGen/read_requirements.swift

@@ -55,7 +55,7 @@ public protocol P1 : ~Copyable {
 // CHECK:        unwind
 // CHECK-LABEL: } // end sil function '$s17read_requirements2P1P4ubgsAA1UVvy'
 
-// CHECK-LABEL: sil [ossa] @$s17read_requirements2P1P4ubgsAA1UVvx : {{.*}} {
+// CHECK-LABEL: sil{{.*}} [ossa] @$s17read_requirements2P1P4ubgsAA1UVvx : {{.*}} {
 // CHECK:       bb0(
 // CHECK-SAME:      [[SELF_UNCHECKED:%[^:]+]]
 // CHECK-SAME:  ):