TypeCheckType: Look through any and some in any syntax checker

Author: AnthonyLatsis

lib/Sema/TypeCheckType.cpp

@@ -5922,21 +5922,46 @@ class ExistentialTypeSyntaxChecker : public ASTWalker {
     if (T->isInvalid())
       return Action::SkipNode();
 
-    // Arbitrary protocol constraints are OK on opaque types.
-    if (isa<OpaqueReturnTypeRepr>(T))
-      return Action::SkipNode();
-
-    // Arbitrary protocol constraints are okay for 'any' types.
-    if (isa<ExistentialTypeRepr>(T))
-      return Action::SkipNode();
-
     reprStack.push_back(T);
 
     auto *declRefTR = dyn_cast<DeclRefTypeRepr>(T);
     if (!declRefTR) {
       return Action::Continue();
     }
 
+    // Determine whether this identifier type is a subject of a `some` or `any`
+    // type and, if so, ignore it, since it already has a keyword applied to it.
+    // For example, `P` is a subject of `any P` and `any Q & (P)`, but
+    // not `any Q<P>`.
+    if (reprStack.size() > 1) {
+      auto it = reprStack.end() - 1;
+      while (true) {
+        --it;
+        if (it == reprStack.begin()) {
+          break;
+        }
+
+        // Look through parens, metatypes, and compositions.
+        if (isa<TupleTypeRepr>(*it) || isa<CompositionTypeRepr>(*it) ||
+            isa<MetatypeTypeRepr>(*it)) {
+          continue;
+        }
+
+        // Look through '?' and '!' too; `any P?` et al. is diagnosed in the
+        // type resolver.
+        if (isa<OptionalTypeRepr>(*it) ||
+            isa<ImplicitlyUnwrappedOptionalTypeRepr>(*it)) {
+          continue;
+        }
+
+        break;
+      }
+
+      if (isa<OpaqueReturnTypeRepr>(*it) || isa<ExistentialTypeRepr>(*it)) {
+        return Action::Continue();
+      }
+    }
+
     // We only care about the type of an outermost member type representation.
     // For example, in `A<T>.B.C<U>`, check `C` and generic arguments `U` and
     // `T`, but not `A` or `B`.

test/type/explicit_existential.swift

@@ -59,6 +59,10 @@ protocol HasAssoc {
   func foo()
 }
 
+protocol HasAssocGeneric<Assoc> {
+  associatedtype Assoc
+}
+
 do {
   enum MyError: Error {
     case bad(Any)
@@ -320,6 +324,17 @@ func testAnyFixIt() {
   // expected-error@+1 {{use of protocol 'HasAssoc' as a type must be written 'any HasAssoc'}}{{10-18=(any HasAssoc)}}
   let _: HasAssoc.Protocol? = (any HasAssoc).self
 
+  // https://github.com/apple/swift/issues/72588
+
+  // expected-error@+1 {{use of protocol 'HasAssoc' as a type must be written 'any HasAssoc'}}{{30-38=any HasAssoc}}
+  let _: any HasAssocGeneric<HasAssoc>
+  // expected-error@+1 {{use of protocol 'HasAssoc' as a type must be written 'any HasAssoc'}}{{31-39=any HasAssoc}}
+  let _: any (HasAssocGeneric<HasAssoc>)
+  // expected-error@+1 {{use of protocol 'HasAssoc' as a type must be written 'any HasAssoc'}}{{35-43=any HasAssoc}}
+  func f1(_: some HasAssocGeneric<HasAssoc> & HasAssoc) {}
+  // expected-error@+1 {{use of protocol 'HasAssoc' as a type must be written 'any HasAssoc'}}{{37-45=any HasAssoc}}
+  func f2(_: some ((HasAssocGeneric<HasAssoc>)) & (HasAssoc)) {}
+
   // expected-error@+1 {{optional 'any' type must be written '(any HasAssoc)?'}}{{10-23=(any HasAssoc)?}}
   let _: any HasAssoc? = nil
   // expected-error@+1 {{optional 'any' type must be written '(any HasAssoc.Type)?'}}{{10-28=(any HasAssoc.Type)?}}
@@ -361,4 +376,4 @@ var example1: any (any IteratorProtocol) = 5 // expected-error{{redundant 'any'
 protocol PP {}
 struct A : PP {}
 let _: any PP = A() // Ok
-let _: any (any PP) = A() // expected-error{{redundant 'any' in type 'any (any PP)'}} {{8-12=}}
+let _: any (any PP) = A() // expected-error{{redundant 'any' in type 'any (any PP)'}} {{8-12=}}

test/type/explicit_existential_swift6.swift

@@ -65,6 +65,10 @@ protocol HasAssoc {
   func foo()
 }
 
+protocol HasAssocGeneric<Assoc> {
+  associatedtype Assoc
+}
+
 do {
   enum MyError: Error {
     case bad(Any)
@@ -92,7 +96,7 @@ func testHasAssoc(_ x: Any, _: any HasAssoc) {
 
     func method() -> any HasAssoc {}
     func existentialArray() ->  [any HasAssoc] {}
-    func existentialcSequence() ->  any Sequence<HasAssoc> {}
+    func existentialcSequence() ->  any Sequence<any HasAssoc> {}
   }
 }
 
@@ -353,6 +357,17 @@ func testAnyFixIt() {
   // expected-error@+1 {{use of protocol 'HasAssoc' as a type must be written 'any HasAssoc'}}{{10-18=(any HasAssoc)}}
   let _: HasAssoc.Protocol? = (any HasAssoc).self
 
+  // https://github.com/apple/swift/issues/72588
+
+  // expected-error@+1 {{use of protocol 'HasAssoc' as a type must be written 'any HasAssoc'}}{{30-38=any HasAssoc}}
+  let _: any HasAssocGeneric<HasAssoc>
+  // expected-error@+1 {{use of protocol 'HasAssoc' as a type must be written 'any HasAssoc'}}{{31-39=any HasAssoc}}
+  let _: any (HasAssocGeneric<HasAssoc>)
+  // expected-error@+1 {{use of protocol 'HasAssoc' as a type must be written 'any HasAssoc'}}{{35-43=any HasAssoc}}
+  func f1(_: some HasAssocGeneric<HasAssoc> & HasAssoc) {}
+  // expected-error@+1 {{use of protocol 'HasAssoc' as a type must be written 'any HasAssoc'}}{{37-45=any HasAssoc}}
+  func f2(_: some ((HasAssocGeneric<HasAssoc>)) & (HasAssoc)) {}
+
   // expected-error@+1 {{optional 'any' type must be written '(any HasAssoc)?'}}{{10-23=(any HasAssoc)?}}
   let _: any HasAssoc? = nil
   // expected-error@+1 {{optional 'any' type must be written '(any HasAssoc.Type)?'}}{{10-28=(any HasAssoc.Type)?}}