[NFC] TypeCheckType: Streamline logic in the any syntax checker

Author: AnthonyLatsis

lib/Sema/TypeCheckType.cpp

@@ -6171,7 +6171,7 @@ namespace {
 /// written syntax.
 class ExistentialTypeSyntaxChecker : public ASTWalker {
   ASTContext &Ctx;
-  bool checkStatements;
+  const bool checkStatements;
   bool hitTopStmt;
   bool warnUntilSwift7;
 
@@ -6215,7 +6215,7 @@ class ExistentialTypeSyntaxChecker : public ASTWalker {
   }
 
   PostWalkAction walkToTypeReprPost(TypeRepr *T) override {
-    assert(reprStack.back() == T);
+    ASSERT(reprStack.back() == T);
     reprStack.pop_back();
     return Action::Continue();
   }
@@ -6339,14 +6339,13 @@ class ExistentialTypeSyntaxChecker : public ASTWalker {
     diag.fixItReplace(replacementT->getSourceRange(), fix);
   }
 
-  /// Returns a Boolean value indicating whether the type representation being
-  /// visited, assuming it is a constraint type demanding `any` or `some`, is
-  /// missing either keyword.
-  bool isAnyOrSomeMissing() const {
-    assert(isa<DeclRefTypeRepr>(reprStack.back()));
+  /// Returns a Boolean value indicating whether the currently visited
+  /// `DeclRefTypeRepr` node has a `some` or `any` keyword that applies to it.
+  bool currentNodeHasAnyOrSomeKeyword() const {
+    ASSERT(isa<DeclRefTypeRepr>(reprStack.back()));
 
     if (reprStack.size() < 2) {
-      return true;
+      return false;
     }
 
     auto it = reprStack.end() - 1;
@@ -6356,7 +6355,7 @@ class ExistentialTypeSyntaxChecker : public ASTWalker {
         break;
       }
 
-      // Look through parens, inverses, metatypes, and compositions.
+      // Look through parens, inverses, `.Type` metatypes, and compositions.
       if ((*it)->isParenType() || isa<InverseTypeRepr>(*it) ||
           isa<CompositionTypeRepr>(*it) || isa<MetatypeTypeRepr>(*it)) {
         continue;
@@ -6365,84 +6364,114 @@ class ExistentialTypeSyntaxChecker : public ASTWalker {
       break;
     }
 
-    return !(isa<OpaqueReturnTypeRepr>(*it) || isa<ExistentialTypeRepr>(*it));
+    return isa<OpaqueReturnTypeRepr>(*it) || isa<ExistentialTypeRepr>(*it);
   }
 
-  void checkDeclRefTypeRepr(DeclRefTypeRepr *T) const {
-    assert(!T->isInvalid());
+  /// Returns the behavior with which to diagnose a missing `any` or `some`
+  /// keyword.
+  ///
+  /// \param constraintTy The constraint type that is missing the keyword.
+  /// \param isInverted Whether the constraint type is an object of an `~`
+  ///  inversion.
+  static bool shouldDiagnoseMissingAnyOrSomeKeyword(Type constraintTy,
+                                                    bool isInverted,
+                                                    ASTContext &ctx) {
+    // `Any` and `AnyObject` are always exempt from `any` syntax.
+    if (constraintTy->isAny() || constraintTy->isAnyObject()) {
+      return false;
+    }
 
-    if (Ctx.LangOpts.hasFeature(Feature::ImplicitSome)) {
-      return;
+    // If the type is inverted, a missing `any` or `some` is always diagnosed.
+    if (isInverted) {
+      return true;
     }
 
-    // Backtrack the stack, looking just through parentheses and metatypes. If
-    // we find an inverse (which always requires `any`), diagnose it specially.
-    if (reprStack.size() > 1) {
-      auto it = reprStack.end() - 2;
-      while (it != reprStack.begin() &&
-             ((*it)->isParenType() || isa<MetatypeTypeRepr>(*it))) {
-        --it;
-        continue;
+    // If one of the protocols is inverted, a missing `any` or `some` is
+    // always diagnosed.
+    if (auto *PCT = constraintTy->getAs<ProtocolCompositionType>()) {
+      if (!PCT->getInverses().empty()) {
+        return true;
       }
+    }
 
-      if (auto *inverse = dyn_cast<InverseTypeRepr>(*it);
-          inverse && isAnyOrSomeMissing()) {
-        auto diag = Ctx.Diags.diagnose(inverse->getTildeLoc(),
-                                       diag::inverse_requires_any);
-        diag.warnUntilSwiftVersionIf(warnUntilSwift7, 7);
-        emitInsertAnyFixit(diag, T);
-        return;
+    // If one of the protocols has "Self or associated type" requirements,
+    // a missing `any` or `some` is always diagnosed.
+    auto layout = constraintTy->getExistentialLayout();
+    for (auto *protoDecl : layout.getProtocols()) {
+      if (protoDecl->existentialRequiresAny()) {
+        return true;
       }
     }
 
+    return false;
+  }
+
+  void checkDeclRefTypeRepr(DeclRefTypeRepr *T) const {
+    if (Ctx.LangOpts.hasFeature(Feature::ImplicitSome)) {
+      return;
+    }
+
     auto *decl = T->getBoundDecl();
     if (!decl) {
       return;
     }
 
-    if (auto *proto = dyn_cast<ProtocolDecl>(decl)) {
-      if (proto->existentialRequiresAny() && isAnyOrSomeMissing()) {
-        auto diag =
-            Ctx.Diags.diagnose(T->getNameLoc(), diag::existential_requires_any,
-                               proto->getDeclaredInterfaceType(),
-                               proto->getDeclaredExistentialType(),
-                               /*isAlias=*/false);
-        diag.warnUntilSwiftVersionIf(warnUntilSwift7, 7);
-        emitInsertAnyFixit(diag, T);
+    if (!isa<ProtocolDecl>(decl) && !isa<TypeAliasDecl>(decl)) {
+      return;
+    }
+
+    // If there is already an `any` or `some` that applies to this node,
+    // move on.
+    if (currentNodeHasAnyOrSomeKeyword()) {
+      return;
+    }
+
+    const auto type = decl->getDeclaredInterfaceType();
+
+    // A type alias may need to be prefixed with `any` only if it stands for a
+    // constraint type.
+    if (isa<TypeAliasDecl>(decl) && !type->isConstraintType()) {
+      return;
+    }
+
+    // First, consider the possibility of the current node being an object of
+    // an inversion, e.g. `~(Copyable)`.
+    // Climb up the stack, looking just through parentheses and `.Type`
+    // metatypes.
+    // If we find an inversion, we will diagnose it specially.
+    InverseTypeRepr *const outerInversion = [&] {
+      if (reprStack.size() < 2) {
+        return (InverseTypeRepr *)nullptr;
       }
-    } else if (auto *alias = dyn_cast<TypeAliasDecl>(decl)) {
-      auto type = Type(alias->getDeclaredInterfaceType()->getDesugaredType());
-
-      // If this is a type alias to a constraint type, the type
-      // alias name must be prefixed with 'any' to be used as an
-      // existential type.
-      if (type->isConstraintType() && !type->isAny() && !type->isAnyObject()) {
-        bool diagnose = false;
-
-        // Look for protocol members that require 'any'.
-        auto layout = type->getExistentialLayout();
-        for (auto *protoDecl : layout.getProtocols()) {
-          if (protoDecl->existentialRequiresAny()) {
-            diagnose = true;
-            break;
-          }
-        }
 
-        // If inverses are present, require 'any' too.
-        if (auto *PCT = type->getAs<ProtocolCompositionType>())
-          diagnose |= !PCT->getInverses().empty();
-
-        if (diagnose && isAnyOrSomeMissing()) {
-          auto diag = Ctx.Diags.diagnose(
-              T->getNameLoc(), diag::existential_requires_any,
-              alias->getDeclaredInterfaceType(),
-              ExistentialType::get(alias->getDeclaredInterfaceType()),
-              /*isAlias=*/true);
-          diag.warnUntilSwiftVersionIf(warnUntilSwift7, 7);
-          emitInsertAnyFixit(diag, T);
-        }
+      auto it = reprStack.end() - 2;
+      while (it != reprStack.begin() &&
+             ((*it)->isParenType() || isa<MetatypeTypeRepr>(*it))) {
+        --it;
+        continue;
       }
+
+      return dyn_cast<InverseTypeRepr>(*it);
+    }();
+
+    if (!shouldDiagnoseMissingAnyOrSomeKeyword(
+            type, /*isInverted=*/outerInversion, this->Ctx)) {
+      return;
+    }
+
+    std::optional<InFlightDiagnostic> diag;
+    if (outerInversion) {
+      diag.emplace(Ctx.Diags.diagnose(outerInversion->getTildeLoc(),
+                                      diag::inverse_requires_any));
+    } else {
+      diag.emplace(Ctx.Diags.diagnose(T->getNameLoc(),
+                                      diag::existential_requires_any, type,
+                                      ExistentialType::get(type),
+                                      /*isAlias=*/isa<TypeAliasDecl>(decl)));
     }
+
+    diag->warnUntilSwiftVersionIf(warnUntilSwift7, 7);
+    emitInsertAnyFixit(*diag, T);
   }
 
 public:

test/decl/protocol/protocols.swift

@@ -112,9 +112,9 @@ struct DoesNotConform : Up {
 // Circular protocols
 
 protocol CircleMiddle : CircleStart { func circle_middle() }
-// expected-note@-1 3 {{protocol 'CircleMiddle' declared here}}
-protocol CircleStart : CircleEnd { func circle_start() } // expected-error 3 {{protocol 'CircleStart' refines itself}}
-protocol CircleEnd : CircleMiddle { func circle_end()} // expected-note 3 {{protocol 'CircleEnd' declared here}}
+// expected-note@-1 2 {{protocol 'CircleMiddle' declared here}}
+protocol CircleStart : CircleEnd { func circle_start() } // expected-error 2 {{protocol 'CircleStart' refines itself}}
+protocol CircleEnd : CircleMiddle { func circle_end()} // expected-note 2 {{protocol 'CircleEnd' declared here}}
 
 protocol CircleEntry : CircleTrivial { }
 protocol CircleTrivial : CircleTrivial { } // expected-error {{protocol 'CircleTrivial' refines itself}}