[torque] use implicit parameters for template parameter inference

This allows templates to preserve the type of implicit parameters to
select a better ovleroad, without generally extending overload
resolution to implicit parameters, which could be confusing.

Bug: v8:7793
Change-Id: Ie57090a295b0b46d03789829b975fc16e2a9c5b9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2329630
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#69177}

src/torque/declarable.cc

@@ -2,10 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "src/torque/declarable.h"
+
 #include <fstream>
 #include <iostream>
 
-#include "src/torque/declarable.h"
+#include "src/torque/ast.h"
 #include "src/torque/global-context.h"
 #include "src/torque/type-inference.h"
 #include "src/torque/type-visitor.h"
@@ -134,17 +136,13 @@ std::vector<TypeConstraint> ComputeConstraints(
 
 TypeArgumentInference GenericCallable::InferSpecializationTypes(
     const TypeVector& explicit_specialization_types,
-    const TypeVector& arguments) {
-  size_t implicit_count = declaration()->parameters.implicit_count;
+    const std::vector<base::Optional<const Type*>>& arguments) {
   const std::vector<TypeExpression*>& parameters =
       declaration()->parameters.types;
-  std::vector<TypeExpression*> explicit_parameters(
-      parameters.begin() + implicit_count, parameters.end());
-
   CurrentScope::Scope generic_scope(ParentScope());
   TypeArgumentInference inference(generic_parameters(),
-                                  explicit_specialization_types,
-                                  explicit_parameters, arguments);
+                                  explicit_specialization_types, parameters,
+                                  arguments);
   if (!inference.HasFailed()) {
     if (auto violation =
             FindConstraintViolation(inference.GetResult(), Constraints())) {

src/torque/declarable.h

@@ -567,7 +567,7 @@ class GenericCallable
 
   TypeArgumentInference InferSpecializationTypes(
       const TypeVector& explicit_specialization_types,
-      const TypeVector& arguments);
+      const std::vector<base::Optional<const Type*>>& arguments);
 
  private:
   friend class Declarations;

src/torque/declaration-visitor.cc

@@ -196,9 +196,10 @@ void DeclarationVisitor::Visit(SpecializationDeclaration* decl) {
     // This argument inference is just to trigger constraint checking on the
     // generic arguments.
     TypeArgumentInference inference = generic->InferSpecializationTypes(
-        TypeVisitor::ComputeTypeVector(decl->generic_parameters),
-        signature_with_types.GetExplicitTypes());
-    if (inference.HasFailed()) continue;
+        TypeVisitor::ComputeTypeVector(decl->generic_parameters), {});
+    if (inference.HasFailed()) {
+      continue;
+    }
     Signature generic_signature_with_types =
         MakeSpecializedSignature(SpecializationKey<GenericCallable>{
             generic, TypeVisitor::ComputeTypeVector(decl->generic_parameters)});

src/torque/implementation-visitor.cc

@@ -1786,6 +1786,25 @@ bool ImplementationVisitor::TestLookupCallable(
                         {}, {}, true) != nullptr;
 }
 
+TypeArgumentInference ImplementationVisitor::InferSpecializationTypes(
+    GenericCallable* generic, const TypeVector& explicit_specialization_types,
+    const TypeVector& explicit_arguments) {
+  std::vector<base::Optional<const Type*>> all_arguments;
+  const ParameterList& parameters = generic->declaration()->parameters;
+  for (size_t i = 0; i < parameters.implicit_count; ++i) {
+    base::Optional<Binding<LocalValue>*> val =
+        TryLookupLocalValue(parameters.names[i]->value);
+    all_arguments.push_back(
+        val ? (*val)->GetLocationReference(*val).ReferencedType()
+            : base::nullopt);
+  }
+  for (const Type* explicit_argument : explicit_arguments) {
+    all_arguments.push_back(explicit_argument);
+  }
+  return generic->InferSpecializationTypes(explicit_specialization_types,
+                                           all_arguments);
+}
+
 template <class Container>
 Callable* ImplementationVisitor::LookupCallable(
     const QualifiedName& name, const Container& declaration_container,
@@ -1799,8 +1818,8 @@ Callable* ImplementationVisitor::LookupCallable(
   std::vector<std::pair<GenericCallable*, std::string>> inapplicable_generics;
   for (auto* declarable : declaration_container) {
     if (GenericCallable* generic = GenericCallable::DynamicCast(declarable)) {
-      TypeArgumentInference inference = generic->InferSpecializationTypes(
-          specialization_types, parameter_types);
+      TypeArgumentInference inference = InferSpecializationTypes(
+          generic, specialization_types, parameter_types);
       if (inference.HasFailed()) {
         inapplicable_generics.push_back(
             std::make_pair(generic, inference.GetFailureReason()));
@@ -1861,8 +1880,8 @@ Callable* ImplementationVisitor::LookupCallable(
 
   if (GenericCallable* generic =
           GenericCallable::DynamicCast(overloads[best])) {
-    TypeArgumentInference inference = generic->InferSpecializationTypes(
-        specialization_types, parameter_types);
+    TypeArgumentInference inference = InferSpecializationTypes(
+        generic, specialization_types, parameter_types);
     result = GetOrCreateSpecialization(
         SpecializationKey<GenericCallable>{generic, inference.GetResult()});
   } else {

src/torque/implementation-visitor.h

@@ -682,6 +682,10 @@ class ImplementationVisitor {
                        const Arguments& arguments,
                        const TypeVector& specialization_types);
 
+  TypeArgumentInference InferSpecializationTypes(
+      GenericCallable* generic, const TypeVector& explicit_specialization_types,
+      const TypeVector& explicit_arguments);
+
   const Type* GetCommonType(const Type* left, const Type* right);
 
   VisitResult GenerateCopy(const VisitResult& to_copy);

src/torque/type-inference.cc

@@ -12,7 +12,7 @@ TypeArgumentInference::TypeArgumentInference(
     const GenericParameters& type_parameters,
     const TypeVector& explicit_type_arguments,
     const std::vector<TypeExpression*>& term_parameters,
-    const TypeVector& term_argument_types)
+    const std::vector<base::Optional<const Type*>>& term_argument_types)
     : num_explicit_(explicit_type_arguments.size()),
       type_parameter_from_name_(type_parameters.size()),
       inferred_(type_parameters.size()) {
@@ -20,8 +20,8 @@ TypeArgumentInference::TypeArgumentInference(
     Fail("more explicit type arguments than expected");
     return;
   }
-  if (term_parameters.size() != term_argument_types.size()) {
-    Fail("number of term parameters does not match number of term arguments!");
+  if (term_argument_types.size() > term_parameters.size()) {
+    Fail("more arguments than expected");
     return;
   }
 
@@ -32,8 +32,9 @@ TypeArgumentInference::TypeArgumentInference(
     inferred_[i] = {explicit_type_arguments[i]};
   }
 
-  for (size_t i = 0; i < term_parameters.size(); i++) {
-    Match(term_parameters[i], term_argument_types[i]);
+  for (size_t i = 0; i < term_argument_types.size(); i++) {
+    if (term_argument_types[i])
+      Match(term_parameters[i], *term_argument_types[i]);
     if (HasFailed()) return;
   }
 

src/torque/type-inference.h

@@ -55,10 +55,11 @@ namespace torque {
 // should be instantiated in the appropriate scope.
 class TypeArgumentInference {
  public:
-  TypeArgumentInference(const GenericParameters& type_parameters,
+  TypeArgumentInference(
+      const GenericParameters& type_parameters,
       const TypeVector& explicit_type_arguments,
       const std::vector<TypeExpression*>& term_parameters,
-                        const TypeVector& term_argument_types);
+      const std::vector<base::Optional<const Type*>>& term_argument_types);
 
   bool HasFailed() const { return failure_reason_.has_value(); }
   const std::string& GetFailureReason() { return *failure_reason_; }

src/torque/type-visitor.cc

@@ -500,9 +500,10 @@ const Type* TypeVisitor::ComputeTypeForStructExpression(
   }
 
   CurrentScope::Scope generic_scope(generic_type->ParentScope());
-  TypeArgumentInference inference(generic_type->generic_parameters(),
-                                  explicit_type_arguments, term_parameters,
-                                  term_argument_types);
+  TypeArgumentInference inference(
+      generic_type->generic_parameters(), explicit_type_arguments,
+      term_parameters,
+      TransformVector<base::Optional<const Type*>>(term_argument_types));
 
   if (inference.HasFailed()) {
     ReportError("failed to infer type arguments for struct ", basic->name,

src/torque/utils.h

@@ -5,6 +5,7 @@
 #ifndef V8_TORQUE_UTILS_H_
 #define V8_TORQUE_UTILS_H_
 
+#include <algorithm>
 #include <ostream>
 #include <queue>
 #include <streambuf>
@@ -523,6 +524,17 @@ class Worklist {
   std::unordered_set<T> contained_;
 };
 
+template <class T, class U, class F>
+std::vector<T> TransformVector(const std::vector<U>& v, F f) {
+  std::vector<T> result;
+  std::transform(v.begin(), v.end(), std::back_inserter(result), f);
+  return result;
+}
+template <class T, class U>
+std::vector<T> TransformVector(const std::vector<U>& v) {
+  return TransformVector<T>(v, [](const U& x) -> T { return x; });
+}
+
 }  // namespace torque
 }  // namespace internal
 }  // namespace v8

test/unittests/torque/torque-unittest.cc

@@ -915,6 +915,48 @@ TEST(Torque, UnusedImplicit) {
                 "Test6(Smi): Smi\n  Test6(implicit Smi)(Smi): Smi"));
 }
 
+TEST(Torque, ImplicitTemplateParameterInference) {
+  ExpectSuccessfulCompilation(R"(
+    macro Foo(_x: Map) {}
+    macro Foo(_x: Smi) {}
+    macro GenericMacro<T: type>(implicit x: T)() {
+      Foo(x);
+    }
+    @export
+    macro Test1(implicit x: Smi)() { GenericMacro(); }
+    @export
+    macro Test2(implicit x: Map)() { GenericMacro();  }
+  )");
+
+  ExpectFailingCompilation(
+      R"(
+    // Wrap in namespace to avoid redeclaration error.
+    namespace foo {
+    macro Foo(implicit x: Map)() {}
+    }
+    macro Foo(implicit x: Smi)() {}
+    namespace foo{
+    @export
+    macro Test(implicit x: Smi)() { Foo(); }
+    }
+  )",
+      HasSubstr("ambiguous callable"));
+
+  ExpectFailingCompilation(
+      R"(
+    // Wrap in namespace to avoid redeclaration error.
+    namespace foo {
+    macro Foo(implicit x: Map)() {}
+    }
+    macro Foo(implicit x: Smi)() {}
+    namespace foo{
+    @export
+    macro Test(implicit x: Map)() { Foo(); }
+    }
+  )",
+      HasSubstr("ambiguous callable"));
+}
+
 }  // namespace torque
 }  // namespace internal
 }  // namespace v8