[SIL] Add isolation captured by @_inheritActorContext(always) while lowering captures

`getLoweredLocalCaptures` seems the best place to do it because
during Sema there is a chicken and an egg situation where isolation
depends on captures and in this case captures depend on isolation.

Author: xedin

lib/SIL/IR/TypeLowering.cpp

@@ -4676,6 +4676,24 @@ TypeConverter::getLoweredLocalCaptures(SILDeclRef fn) {
 
   collectConstantCaptures(fn);
 
+  // @_inheritActorContext(always) attribute allows implicit
+  // capture of isolation parameter from the context. This
+  // cannot be done as part of computing captures because
+  // isolation is not available at that point because it in
+  // turn depends on captures sometimes.
+  if (auto *closure = fn.getClosureExpr()) {
+    if (closure->alwaysInheritsActorContext()) {
+      auto isolation = closure->getActorIsolation();
+      if (isolation.isActorInstanceIsolated()) {
+        if (auto *var = isolation.getActorInstance()) {
+          recordCapture(CapturedValue(var, /*flags=*/0, SourceLoc()));
+        } else if (auto *actorExpr = isolation.getActorInstanceExpr()) {
+          recordCapture(CapturedValue(actorExpr, /*flags=*/0));
+        }
+      }
+    }
+  }
+
   SmallVector<CapturedValue, 4> resultingCaptures;
   for (auto capturePair : varCaptures) {
     resultingCaptures.push_back(capturePair.second);

test/SILGen/hop_to_executor.swift

@@ -324,6 +324,7 @@ func testGlobalActorFuncValue(_ fn: @RedActor () -> Void) async {
 }
 
 func acceptAsyncSendableClosureInheriting<T>(@_inheritActorContext _: @Sendable () async -> T) { }
+func acceptAsyncSendableClosureAlwaysInheriting<T>(@_inheritActorContext(always) _: @Sendable () async -> T) { }
 
 extension MyActor {
   func synchronous() { }
@@ -338,6 +339,50 @@ extension MyActor {
       synchronous()
     }
   }
+
+  // CHECK-LABEL: sil private [ossa] @$s4test7MyActorC0A16AlwaysInheritingyyFyyYaYbXEfU_
+  // CHECK: debug_value [[SELF:%[0-9]+]] : $MyActor
+  // CHECK-NEXT: [[COPY:%[0-9]+]] = copy_value [[SELF]] : $MyActor
+  // CHECK-NEXT: [[BORROW:%[0-9]+]] = begin_borrow [[COPY]] : $MyActor
+  // CHECK-NEXT: hop_to_executor [[BORROW]] : $MyActor
+  func testAlwaysInheriting() {
+    acceptAsyncSendableClosureAlwaysInheriting {
+    }
+  }
+}
+
+func testIsolatedParameterWithInheritActorContext(_ isolation: isolated (any Actor)?) {
+  // CHECK-LABEL: sil private [ossa] @$s4test0A40IsolatedParameterWithInheritActorContextyyScA_pSgYiFyyYaYbXEfU_
+  // CHECK: debug_value [[ISOLATION:%[0-9]+]] : $Optional<any Actor>
+  // CHECK-NEXT: [[COPY:%[0-9]+]] = copy_value [[ISOLATION]] : $Optional<any Actor>
+  // CHECK-NEXT: [[BORROW:%[0-9]+]] = begin_borrow [[COPY]] : $Optional<any Actor>
+  // CHECK-NEXT: hop_to_executor [[BORROW]] : $Optional<any Actor>
+  acceptAsyncSendableClosureAlwaysInheriting {
+  }
+
+  // CHECK-LABEL: sil private [ossa] @$s4test0A40IsolatedParameterWithInheritActorContextyyScA_pSgYiFyyYaYbScMYcXEfU0_
+  // CHECK: hop_to_executor {{.*}} : $MainActor
+  acceptAsyncSendableClosureAlwaysInheriting { @MainActor in
+    // CHECK-LABEL: sil private [ossa] @$s4test0A40IsolatedParameterWithInheritActorContextyyScA_pSgYiFyyYaYbScMYcXEfU0_yyYaYbXEfU_
+    // CHECK: hop_to_executor {{.*}} : $MainActor
+    acceptAsyncSendableClosureAlwaysInheriting {
+    }
+  }
+
+  // CHECK-LABEL: sil private [ossa] @$s4test0A40IsolatedParameterWithInheritActorContextyyScA_pSgYiFyyYaYbXEfU1_
+  // CHECK: debug_value [[ISOLATION:%[0-9]+]] : $Optional<any Actor>
+  // CHECK-NEXT: [[COPY:%[0-9]+]] = copy_value [[ISOLATION]] : $Optional<any Actor>
+  // CHECK-NEXT: [[BORROW:%[0-9]+]] = begin_borrow [[COPY]] : $Optional<any Actor>
+  // CHECK-NEXT: hop_to_executor [[BORROW]] : $Optional<any Actor>
+  acceptAsyncSendableClosureAlwaysInheriting {
+    // CHECK-LABEL: sil private [ossa] @$s4test0A40IsolatedParameterWithInheritActorContextyyScA_pSgYiFyyYaYbXEfU1_yyYaYbXEfU_
+    // CHECK: debug_value [[ISOLATION:%[0-9]+]] : $Optional<any Actor>
+    // CHECK-NEXT: [[COPY:%[0-9]+]] = copy_value [[ISOLATION]] : $Optional<any Actor>
+    // CHECK-NEXT: [[BORROW:%[0-9]+]] = begin_borrow [[COPY]] : $Optional<any Actor>
+    // CHECK-NEXT: hop_to_executor [[BORROW]] : $Optional<any Actor>
+    acceptAsyncSendableClosureAlwaysInheriting {
+    }
+  }
 }
 
 func acceptAsyncClosure(_: () async -> Void) { }