Swift: extract existential types

Author: redsun82

swift/codegen/schema.yml

@@ -115,6 +115,7 @@ ProtocolCompositionType:
 
 ExistentialType:
   _extends: Type
+  constraint: Type
 
 ReferenceStorageType:
   _extends: Type

swift/extractor/visitors/TypeVisitor.cpp

@@ -253,5 +253,11 @@ void TypeVisitor::fillArchetypeType(const swift::ArchetypeType& type, ArchetypeT
   entry.superclass = dispatcher_.fetchOptionalLabel(type.getSuperclass());
   fillType(type, entry);
 }
+codeql::ExistentialType TypeVisitor::translateExistentialType(const swift::ExistentialType& type) {
+  codeql::ExistentialType entry{dispatcher_.assignNewLabel(type)};
+  entry.constraint = dispatcher_.fetchLabel(type.getConstraintType());
+  fillType(type, entry);
+  return entry;
+}
 
 }  // namespace codeql

swift/extractor/visitors/TypeVisitor.h

@@ -38,6 +38,7 @@ class TypeVisitor : public TypeVisitorBase<TypeVisitor> {
   codeql::PrimaryArchetypeType translatePrimaryArchetypeType(
       const swift::PrimaryArchetypeType& type);
   codeql::NestedArchetypeType translateNestedArchetypeType(const swift::NestedArchetypeType& type);
+  codeql::ExistentialType translateExistentialType(const swift::ExistentialType& type);
 
  private:
   void fillType(const swift::TypeBase& type, codeql::Type& entry);

swift/ql/lib/codeql/swift/elements/type/ExistentialType.qll

@@ -1,4 +1,6 @@
-// generated by codegen/codegen.py, remove this comment if you wish to edit this file
 private import codeql.swift.generated.type.ExistentialType
+private import codeql.swift.elements.type.ProtocolType
 
-class ExistentialType extends ExistentialTypeBase { }
+class ExistentialType extends ExistentialTypeBase {
+  override ProtocolType getConstraint() { result = super.getConstraint() }
+}

swift/ql/lib/codeql/swift/generated/type/ExistentialType.qll

@@ -3,4 +3,11 @@ import codeql.swift.elements.type.Type
 
 class ExistentialTypeBase extends @existential_type, Type {
   override string getAPrimaryQlClass() { result = "ExistentialType" }
+
+  Type getConstraint() {
+    exists(Type x |
+      existential_types(this, x) and
+      result = x.resolve()
+    )
+  }
 }

swift/ql/lib/swift.dbscheme

@@ -273,7 +273,8 @@ protocol_composition_types(  //dir=type
 );
 
 existential_types(  //dir=type
-  unique int id: @existential_type
+  unique int id: @existential_type,
+  int constraint: @type ref
 );
 
 @reference_storage_type =

swift/ql/test/extractor-tests/generated/type/ExistentialType/ExistentialType.expected

@@ -0,0 +1,2 @@
+| ExplicitExistential | getDiagnosticsName: | ExplicitExistential | getCanonicalType: | ExplicitExistential | getConstraint: | ExplicitExistential |
+| ImplicitExistential | getDiagnosticsName: | ImplicitExistential | getCanonicalType: | ImplicitExistential | getConstraint: | ImplicitExistential |

swift/ql/test/extractor-tests/generated/type/ExistentialType/ExistentialType.ql

@@ -0,0 +1,13 @@
+// generated by codegen/codegen.py
+import codeql.swift.elements
+import TestUtils
+
+from ExistentialType x, string getDiagnosticsName, Type getCanonicalType, Type getConstraint
+where
+  toBeTested(x) and
+  not x.isUnknown() and
+  getDiagnosticsName = x.getDiagnosticsName() and
+  getCanonicalType = x.getCanonicalType() and
+  getConstraint = x.getConstraint()
+select x, "getDiagnosticsName:", getDiagnosticsName, "getCanonicalType:", getCanonicalType,
+  "getConstraint:", getConstraint

swift/ql/test/extractor-tests/generated/type/ExistentialType/MISSING_SOURCE.txt

@@ -0,0 +1,5 @@
+protocol ExplicitExistential {}
+protocol ImplicitExistential {}
+
+func foo1(_: any ExplicitExistential) {}
+func foo2(_: ImplicitExistential) {}  // valid for now, will be an error in some future swift release