[region-isolation] Fix code where we were not properly mapping a type into a SILFunction's context to actually do so.

rdar://138667211

Author: gottesmm

lib/SILOptimizer/Mandatory/SendNonSendable.cpp

@@ -1667,6 +1667,7 @@ bool SentNeverSendableDiagnosticInferrer::initForSendingPartialApply(
   for (auto capture : ce->getCaptureInfo().getCaptures()) {
     auto *decl = capture.getDecl();
     auto type = decl->getInterfaceType()->getCanonicalType();
+    type = pai->getFunction()->mapTypeIntoContext(type)->getCanonicalType();
     auto silType = SILType::getPrimitiveObjectType(type);
     if (!SILIsolationInfo::isNonSendableType(silType, pai->getFunction()))
       continue;

test/Concurrency/transfernonsendable.swift

@@ -1906,3 +1906,20 @@ func offByOneWithImplicitPartialApply() {
       }
   }
 }
+
+protocol Progress {
+  associatedtype AssocType
+  var x: AssocType { get }
+  func checkCancellation() throws
+}
+
+// We used to crash here since the closure diagnostic would not map z's type
+// into the current context.
+func testCaptureDiagnosticMapsTypeIntoContext<T : Progress>(_ x: NonSendableKlass, y: T) async throws {
+  let z = y.x
+  await withTaskGroup(of: Void.self) { group in
+    group.addTask { // expected-tns-warning {{passing closure as a 'sending' parameter risks causing data races between code in the current task and concurrent execution of the closure}}
+      print(z) // expected-tns-note {{closure captures 'z' which is accessible to code in the current task}}
+    }
+  }
+}