Merge pull request swiftlang#30221 from CodaFi/existaxis

[CS] Use The Full Opened Type When Forming Subscripts

Author: CodaFi

lib/Sema/CSApply.cpp

@@ -1408,13 +1408,12 @@ namespace {
       // Compute the concrete reference to the subscript.
       auto subscriptRef = resolveConcreteDeclRef(subscript, memberLoc);
 
-      // Figure out the index and result types.
-      auto subscriptTy = simplifyType(selected.openedType);
-      auto *subscriptFnTy = subscriptTy->castTo<FunctionType>();
-      auto resultTy = subscriptFnTy->getResult();
-
       // Coerce the index argument.
-      index = coerceCallArguments(index, subscriptFnTy, subscriptRef, nullptr,
+      auto openedFullFnType = simplifyType(selected.openedFullType)
+                                  ->castTo<FunctionType>();
+      auto fullSubscriptTy = openedFullFnType->getResult()
+                                  ->castTo<FunctionType>();
+      index = coerceCallArguments(index, fullSubscriptTy, subscriptRef, nullptr,
                                   argLabels, hasTrailingClosure,
                                   locator.withPathElement(
                                     ConstraintLocator::ApplyArgument));
@@ -1436,14 +1435,18 @@ namespace {
         // TODO: diagnose if semantics != AccessSemantics::Ordinary?
         auto subscriptExpr = DynamicSubscriptExpr::create(
             ctx, base, index, subscriptRef, isImplicit, getType);
+        auto resultTy = simplifyType(selected.openedType)
+                            ->castTo<FunctionType>()
+                            ->getResult();
+        assert(!selected.openedFullType->hasOpenedExistential()
+               && "open existential archetype in AnyObject subscript type?");
         cs.setType(subscriptExpr, resultTy);
         Expr *result = subscriptExpr;
         closeExistential(result, locator);
         return result;
       }
 
       // Convert the base.
-      auto openedFullFnType = selected.openedFullType->castTo<FunctionType>();
       auto openedBaseType =
           getBaseType(openedFullFnType, /*wantsRValue*/ false);
       auto containerTy = solution.simplifyType(openedBaseType);
@@ -1469,7 +1472,7 @@ namespace {
       // Form the subscript expression.
       auto subscriptExpr = SubscriptExpr::create(
           ctx, base, index, subscriptRef, isImplicit, semantics, getType);
-      cs.setType(subscriptExpr, resultTy);
+      cs.setType(subscriptExpr, fullSubscriptTy->getResult());
       subscriptExpr->setIsSuper(isSuper);
 
       Expr *result = subscriptExpr;

test/SILGen/protocols.swift

@@ -429,6 +429,22 @@ public func test(_ p: Proto) {
 // CHECK: end_apply [[TOKEN]]
 // CHECK: return
 
+// SR-11748
+
+protocol SelfReturningSubscript {
+  subscript(b: Int) -> Self { get }
+}
+
+public func testSelfReturningSubscript() {
+  // CHECK-LABEL: sil private [ossa] @$s9protocols26testSelfReturningSubscriptyyFAA0cdE0_pAaC_pXEfU_
+  // CHECK: [[OPEN:%.*]] = open_existential_addr immutable_access
+  // CHECK: [[OPEN_ADDR:%.*]] = alloc_stack $@opened("{{.*}}") SelfReturningSubscript
+  // CHECK: copy_addr [[OPEN]] to [initialization] [[OPEN_ADDR]] : $*@opened("{{.*}}") SelfReturningSubscript
+  // CHECK: [[WIT_M:%.*]] = witness_method $@opened("{{.*}}") SelfReturningSubscript, #SelfReturningSubscript.subscript!getter.1
+  // CHECK: apply [[WIT_M]]<@opened("{{.*}}") SelfReturningSubscript>({{%.*}}, {{%.*}}, [[OPEN_ADDR]])
+  _ = [String: SelfReturningSubscript]().mapValues { $0[2] }
+}
+
 // CHECK-LABEL: sil_witness_table hidden ClassWithGetter: PropertyWithGetter module protocols {
 // CHECK-NEXT:  method #PropertyWithGetter.a!getter.1: {{.*}} : @$s9protocols15ClassWithGetterCAA08PropertycD0A2aDP1aSivgTW
 // CHECK-NEXT: }