[region-isolation] Convert emitTypedIsolationCrossingDueToCapture error to use a new form of error.

NOTE: To make testing these easier (since they are fallback paths), I
added an option that disables named errors only for use in asserts.

Author: gottesmm

include/swift/AST/DiagnosticsSIL.def

@@ -948,9 +948,6 @@ ERROR(regionbasedisolation_unknown_pattern, none,
 // Old Transfer Non Sendable Diagnostics
 //
 
-ERROR(regionbasedisolation_isolated_capture_yields_race, none,
-      "%1 closure captures value of non-Sendable type %0 from %2 context; later accesses to value could race",
-      (Type, ActorIsolation, ActorIsolation))
 ERROR(regionbasedisolation_transfer_yields_race_stronglytransferred_binding, none,
       "value of non-Sendable type %0 accessed after being transferred; later accesses could race",
       (Type))
@@ -981,6 +978,9 @@ NOTE(regionbasedisolation_type_use_after_transfer, none,
 NOTE(regionbasedisolation_type_use_after_transfer_callee, none,
       "sending value of non-Sendable type %0 to %1 %2 %3 risks causing data races between %1 and local %4 uses",
       (Type, ActorIsolation, DescriptiveDeclKind, DeclName, ActorIsolation))
+NOTE(regionbasedisolation_type_isolated_capture_yields_race, none,
+      "sending value of non-Sendable type %0 to %1 closure due to closure capture risks causing races in between %1 and %2 uses",
+      (Type, ActorIsolation, ActorIsolation))
 
 ERROR(regionbasedisolation_inout_sending_cannot_be_actor_isolated, none,
       "'inout sending' parameter %0 cannot be %1at end of function",

lib/SILOptimizer/Mandatory/TransferNonSendable.cpp

@@ -779,11 +779,13 @@ class UseAfterTransferDiagnosticEmitter {
   void emitTypedIsolationCrossingDueToCapture(
       SILLocation loc, Type inferredType,
       ApplyIsolationCrossing isolationCrossing) {
-    diagnoseError(loc, diag::regionbasedisolation_isolated_capture_yields_race,
-                  inferredType, isolationCrossing.getCalleeIsolation(),
-                  isolationCrossing.getCallerIsolation())
-        .highlight(loc.getSourceRange())
+    diagnoseError(loc, diag::regionbasedisolation_type_transfer_yields_race,
+                  inferredType)
         .limitBehaviorIf(getBehaviorLimit());
+    diagnoseNote(loc,
+                 diag::regionbasedisolation_type_isolated_capture_yields_race,
+                 inferredType, isolationCrossing.getCalleeIsolation(),
+                 isolationCrossing.getCallerIsolation());
     emitRequireInstDiagnostics();
   }
 

test/Concurrency/transfernonsendable_typed_errors.swift

@@ -29,3 +29,12 @@ func simpleUseAfterFree() async {
   // expected-note @-1 {{sending value of non-Sendable type 'NonSendableKlass' to main actor-isolated global function 'transferToMain' risks causing data races between main actor-isolated and local nonisolated uses}}
   print(x) // expected-note {{access can happen concurrently}}
 }
+
+func isolatedClosureTest() async {
+  let x = NonSendableKlass()
+  let _ = { @MainActor in
+      print(x) // expected-error {{sending value of non-Sendable type 'NonSendableKlass' risks causing data races}}
+      // expected-note @-1 {{sending value of non-Sendable type 'NonSendableKlass' to main actor-isolated closure due to closure capture risks causing races in between main actor-isolated and nonisolated uses}}
+  }
+  print(x) // expected-note {{access can happen concurrently}}
+}