RequirementMachine: New GenericSignature::isValidTypeInContext() query

Author: slavapestov

include/swift/AST/GenericSignature.h

@@ -390,6 +390,8 @@ class alignas(1 << TypeAlignInBits) GenericSignatureImpl final
 
   bool isCanonicalTypeInContext(Type type) const;
 
+  bool isValidTypeInContext(Type type) const;
+
   /// Retrieve the conformance access path used to extract the conformance of
   /// interface \c type to the given \c protocol.
   ///

lib/AST/GenericSignature.cpp

@@ -466,6 +466,19 @@ CanType GenericSignatureImpl::getCanonicalTypeInContext(Type type) const {
       type, { })->getCanonicalType();
 }
 
+bool GenericSignatureImpl::isValidTypeInContext(Type type) const {
+  auto &ctx = getASTContext();
+  switch (ctx.LangOpts.EnableRequirementMachine) {
+  case RequirementMachineMode::Disabled:
+    llvm::errs() << "Not implemented\n";
+    abort();
+
+  case RequirementMachineMode::Enabled:
+  case RequirementMachineMode::Verify:
+    return getRequirementMachine()->isValidTypeInContext(type);
+  }
+}
+
 ArrayRef<CanTypeWrapper<GenericTypeParamType>>
 CanGenericSignature::getGenericParams() const {
   auto params = getPointer()->getGenericParams().getOriginalArray();

lib/AST/RequirementMachine/GenericSignatureQueries.cpp

@@ -431,6 +431,19 @@ Type RequirementMachine::getCanonicalTypeInContext(
   });
 }
 
+/// Determine if the given type parameter is valid with respect to this
+/// requirement machine's generic signature.
+bool RequirementMachine::isValidTypeInContext(Type type) const {
+  assert(type->isTypeParameter());
+
+  auto term = Context.getMutableTermForType(type->getCanonicalType(),
+                                            /*proto=*/nullptr);
+  System.simplify(term);
+
+  auto prefix = getLongestValidPrefix(term);
+  return (prefix == term);
+}
+
 /// Retrieve the conformance access path used to extract the conformance of
 /// interface \c type to the given \c protocol.
 ///

lib/AST/RequirementMachine/RequirementMachine.h

@@ -129,6 +129,7 @@ class RequirementMachine final {
   bool isCanonicalTypeInContext(Type type) const;
   Type getCanonicalTypeInContext(Type type,
                       TypeArrayView<GenericTypeParamType> genericParams) const;
+  bool isValidTypeInContext(Type type) const;
   ConformanceAccessPath getConformanceAccessPath(Type type,
                                                  ProtocolDecl *protocol);
   TypeDecl *lookupNestedType(Type depType, Identifier name) const;