Revert "[Sema] Add specialization constraints for func and variable types, then diagnose w/fixes."

include/swift/AST/DiagnosticsSema.def

@@ -4605,6 +4605,8 @@ NOTE(duplicated_key_declared_here, none,
 // Generic specializations
 ERROR(cannot_explicitly_specialize_generic_function,none,
       "cannot explicitly specialize a generic function", ())
+ERROR(not_a_generic_definition,none,
+      "cannot specialize a non-generic definition", ())
 ERROR(not_a_generic_type,none,
       "cannot specialize non-generic type %0", (Type))
 ERROR(protocol_declares_unknown_primary_assoc_type,none,

include/swift/Sema/CSFix.h

@@ -462,12 +462,9 @@ enum class FixKind : uint8_t {
   /// because its name doesn't appear in 'initializes' or 'accesses' attributes.
   AllowInvalidMemberReferenceInInitAccessor,
 
-  /// Ignore an attempt to specialize a non-generic type.
+  /// Ignore an attempt to specialize non-generic type.
   AllowConcreteTypeSpecialization,
 
-  /// Ignore an attempt to specialize a generic function.
-  AllowGenericFunctionSpecialization,
-
   /// Ignore an out-of-place \c then statement.
   IgnoreOutOfPlaceThenStmt,
 
@@ -3746,33 +3743,6 @@ class AllowConcreteTypeSpecialization final : public ConstraintFix {
   }
 };
 
-class AllowGenericFunctionSpecialization final : public ConstraintFix {
-  ValueDecl *Decl;
-
-  AllowGenericFunctionSpecialization(ConstraintSystem &cs, ValueDecl *decl,
-                                     ConstraintLocator *locator)
-      : ConstraintFix(cs, FixKind::AllowConcreteTypeSpecialization, locator),
-        Decl(decl) {}
-
-public:
-  std::string getName() const override {
-    return "allow generic function specialization";
-  }
-
-  bool diagnose(const Solution &solution, bool asNote = false) const override;
-
-  bool diagnoseForAmbiguity(CommonFixesArray commonFixes) const override {
-    return diagnose(*commonFixes.front().first);
-  }
-
-  static AllowGenericFunctionSpecialization *
-  create(ConstraintSystem &cs, ValueDecl *decl, ConstraintLocator *locator);
-
-  static bool classof(const ConstraintFix *fix) {
-    return fix->getKind() == FixKind::AllowGenericFunctionSpecialization;
-  }
-};
-
 class IgnoreOutOfPlaceThenStmt final : public ConstraintFix {
   IgnoreOutOfPlaceThenStmt(ConstraintSystem &cs, ConstraintLocator *locator)
       : ConstraintFix(cs, FixKind::IgnoreOutOfPlaceThenStmt, locator) {}

lib/Parse/ParseType.cpp

@@ -1476,9 +1476,7 @@ static bool isGenericTypeDisambiguatingToken(Parser &P) {
   auto &tok = P.Tok;
   switch (tok.getKind()) {
   default:
-    // If this is the end of the expr (wouldn't match parseExprSequenceElement),
-    // prefer generic type list over an illegal unary postfix '>' operator.
-    return P.isStartOfSwiftDecl() || P.isStartOfStmt(/*prefer expr=*/true);
+    return false;
   case tok::r_paren:
   case tok::r_square:
   case tok::l_brace:

lib/Sema/CSDiagnostics.cpp

@@ -9360,12 +9360,7 @@ bool InvalidMemberReferenceWithinInitAccessor::diagnoseAsError() {
 }
 
 bool ConcreteTypeSpecialization::diagnoseAsError() {
-  emitDiagnostic(diag::not_a_generic_type, resolveType(ConcreteType));
-  return true;
-}
-
-bool GenericFunctionSpecialization::diagnoseAsError() {
-  emitDiagnostic(diag::cannot_explicitly_specialize_generic_function);
+  emitDiagnostic(diag::not_a_generic_type, ConcreteType);
   return true;
 }
 

lib/Sema/CSDiagnostics.h

@@ -3132,18 +3132,7 @@ class ConcreteTypeSpecialization final : public FailureDiagnostic {
   ConcreteTypeSpecialization(const Solution &solution, Type concreteTy,
                              ConstraintLocator *locator)
       : FailureDiagnostic(solution, locator),
-        ConcreteType(concreteTy) {}
-
-  bool diagnoseAsError() override;
-};
-
-class GenericFunctionSpecialization final : public FailureDiagnostic {
-  ValueDecl *Decl;
-
-public:
-  GenericFunctionSpecialization(const Solution &solution, ValueDecl *decl,
-                                ConstraintLocator *locator)
-      : FailureDiagnostic(solution, locator), Decl(decl) {}
+        ConcreteType(resolveType(concreteTy)) {}
 
   bool diagnoseAsError() override;
 };

lib/Sema/CSFix.cpp

@@ -2616,18 +2616,6 @@ AllowConcreteTypeSpecialization::create(ConstraintSystem &cs, Type concreteTy,
       AllowConcreteTypeSpecialization(cs, concreteTy, locator);
 }
 
-bool AllowGenericFunctionSpecialization::diagnose(const Solution &solution,
-                                                  bool asNote) const {
-  GenericFunctionSpecialization failure(solution, Decl, getLocator());
-  return failure.diagnose(asNote);
-}
-
-AllowGenericFunctionSpecialization *AllowGenericFunctionSpecialization::create(
-    ConstraintSystem &cs, ValueDecl *decl, ConstraintLocator *locator) {
-  return new (cs.getAllocator())
-      AllowGenericFunctionSpecialization(cs, decl, locator);
-}
-
 bool IgnoreOutOfPlaceThenStmt::diagnose(const Solution &solution,
                                         bool asNote) const {
   OutOfPlaceThenStmtFailure failure(solution, getLocator());

lib/Sema/CSGen.cpp

@@ -1903,9 +1903,9 @@ namespace {
     /// introduce them as an explicit generic arguments constraint.
     ///
     /// \returns true if resolving any of the specialization types failed.
-    void addSpecializationConstraint(ConstraintLocator *locator, Type boundType,
-                                     SourceLoc lAngleLoc,
-                                     ArrayRef<TypeRepr *> specializationArgs) {
+    bool addSpecializationConstraint(
+        ConstraintLocator *locator, Type boundType,
+        ArrayRef<TypeRepr *> specializationArgs) {
       // Resolve each type.
       SmallVector<Type, 2> specializationArgTypes;
       auto options =
@@ -1916,36 +1916,61 @@ namespace {
           options |= TypeResolutionFlags::AllowPackReferences;
           elementEnv = OuterExpansions.back();
         }
-        auto result = TypeResolution::resolveContextualType(
+        const auto result = TypeResolution::resolveContextualType(
             specializationArg, CurDC, options,
             // Introduce type variables for unbound generics.
             OpenUnboundGenericType(CS, locator),
             HandlePlaceholderType(CS, locator),
             OpenPackElementType(CS, locator, elementEnv));
-        if (result->hasError()) {
-          auto &ctxt = CS.getASTContext();
-          auto *repr = new (ctxt) PlaceholderTypeRepr(specializationArg->getLoc());
-          result = PlaceholderType::get(ctxt, repr);
-          ctxt.Diags.diagnose(lAngleLoc,
-                              diag::while_parsing_as_left_angle_bracket);
-        }
+        if (result->hasError())
+          return true;
+
         specializationArgTypes.push_back(result);
       }
 
-      auto constraint = Constraint::create(
-          CS, ConstraintKind::ExplicitGenericArguments, boundType,
-          PackType::get(CS.getASTContext(), specializationArgTypes), locator);
-      CS.addUnsolvedConstraint(constraint);
-      CS.activateConstraint(constraint);
+      CS.addConstraint(
+          ConstraintKind::ExplicitGenericArguments, boundType,
+          PackType::get(CS.getASTContext(), specializationArgTypes),
+          locator);
+      return false;
     }
 
     Type visitUnresolvedSpecializeExpr(UnresolvedSpecializeExpr *expr) {
       auto baseTy = CS.getType(expr->getSubExpr());
-      auto *overloadLocator = CS.getConstraintLocator(expr->getSubExpr());
-      addSpecializationConstraint(
-          overloadLocator, baseTy->getMetatypeInstanceType(),
-          expr->getLAngleLoc(), expr->getUnresolvedParams());
-      return baseTy;
+
+      if (baseTy->isTypeVariableOrMember()) {
+        return baseTy;
+      }
+
+      // We currently only support explicit specialization of generic types.
+      // FIXME: We could support explicit function specialization.
+      auto &de = CS.getASTContext().Diags;
+      if (baseTy->is<AnyFunctionType>()) {
+        de.diagnose(expr->getSubExpr()->getLoc(),
+                    diag::cannot_explicitly_specialize_generic_function);
+        de.diagnose(expr->getLAngleLoc(),
+                    diag::while_parsing_as_left_angle_bracket);
+        return Type();
+      }
+
+      if (AnyMetatypeType *meta = baseTy->getAs<AnyMetatypeType>()) {
+        auto *overloadLocator = CS.getConstraintLocator(expr->getSubExpr());
+        if (addSpecializationConstraint(overloadLocator,
+                                        meta->getInstanceType(),
+                                        expr->getUnresolvedParams())) {
+          return Type();
+        }
+
+        return baseTy;
+      }
+
+      // FIXME: If the base type is a type variable, constrain it to a metatype
+      // of a bound generic type.
+      de.diagnose(expr->getSubExpr()->getLoc(),
+                  diag::not_a_generic_definition);
+      de.diagnose(expr->getLAngleLoc(),
+                  diag::while_parsing_as_left_angle_bracket);
+      return Type();
     }
 
     Type visitSequenceExpr(SequenceExpr *expr) {
@@ -4055,9 +4080,10 @@ namespace {
 
       // Add explicit generic arguments, if there were any.
       if (expr->getGenericArgsRange().isValid()) {
-        addSpecializationConstraint(CS.getConstraintLocator(expr), macroRefType,
-                                    expr->getGenericArgsRange().Start,
-                                    expr->getGenericArgs());
+        if (addSpecializationConstraint(
+              CS.getConstraintLocator(expr), macroRefType,
+              expr->getGenericArgs()))
+          return Type();
       }
 
       // Form the applicable-function constraint. The result type

lib/Sema/CSSimplify.cpp

@@ -13950,8 +13950,6 @@ ConstraintSystem::simplifyExplicitGenericArgumentsConstraint(
 
   // Bail out if we haven't selected an overload yet.
   auto simplifiedBoundType = simplifyType(type1, flags);
-  if (simplifiedBoundType->isPlaceholder())
-    return SolutionKind::Solved;
   if (simplifiedBoundType->isTypeVariableOrMember())
     return formUnsolved();
 
@@ -14044,12 +14042,13 @@ ConstraintSystem::simplifyExplicitGenericArgumentsConstraint(
     }
   }
 
+  if (!decl->getAsGenericContext())
+    return SolutionKind::Error;
+
   auto genericParams = getGenericParams(decl);
-  if (!decl->getAsGenericContext() || !genericParams) {
-    return recordFix(AllowConcreteTypeSpecialization::create(
-               *this, type1, getConstraintLocator(locator)))
-               ? SolutionKind::Error
-               : SolutionKind::Solved;
+  if (!genericParams) {
+    // FIXME: Record an error here that we're ignoring the parameters.
+    return SolutionKind::Solved;
   }
 
   // Map the generic parameters we have over to their opened types.
@@ -14082,14 +14081,12 @@ ConstraintSystem::simplifyExplicitGenericArgumentsConstraint(
     }
   }
 
-  // FIXME: We could support explicit function specialization.
-  if (openedGenericParams.empty() ||
-      (isa<AbstractFunctionDecl>(decl) && !hasParameterPack)) {
+  if (openedGenericParams.empty()) {
     if (!shouldAttemptFixes())
       return SolutionKind::Error;
 
-    return recordFix(AllowGenericFunctionSpecialization::create(
-               *this, decl, getConstraintLocator(locator)))
+    return recordFix(AllowConcreteTypeSpecialization::create(
+               *this, type1, getConstraintLocator(locator)))
                ? SolutionKind::Error
                : SolutionKind::Solved;
   }
@@ -15220,7 +15217,6 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyFixConstraint(
   case FixKind::AllowAssociatedValueMismatch:
   case FixKind::GenericArgumentsMismatch:
   case FixKind::AllowConcreteTypeSpecialization:
-  case FixKind::AllowGenericFunctionSpecialization:
   case FixKind::IgnoreGenericSpecializationArityMismatch:
   case FixKind::IgnoreKeyPathSubscriptIndexMismatch:
   case FixKind::AllowMemberRefOnExistential: {

test/Constraints/ambiguous_specialized_name_diagnostics.swift

@@ -42,6 +42,7 @@ func test() {
 
   S<Int>(t: 42).test() // expected-error {{ambiguous use of 'init(t:)'}}
 
+  // FIXME(diagnostics): This should produce ambiguity diagnostic too
   S<Int>.staticFn()
-  // expected-error@-1 {{ambiguous use of 'staticFn()'}}
+  // expected-error@-1 {{generic parameter 'T' could not be inferred}}
 }

test/Parse/enum_element_pattern_swift4.swift

@@ -9,13 +9,10 @@ enum E {
 
   static func testE(e: E) {
     switch e {
-    case A<UndefinedTy>(): // expected-error {{cannot find type 'UndefinedTy' in scope}}
+    case A<UndefinedTy>(): // expected-error {{cannot specialize a non-generic definition}}
     // expected-note@-1 {{while parsing this '<' as a type parameter bracket}}
-    // expected-error@-2 {{cannot specialize non-generic type 'E'}}
-    // expected-error@-3 {{cannot call value of non-function type 'E'}}
       break
-    case B<Int>(): // expected-error {{cannot specialize non-generic type 'E'}}
-    // expected-error@-1 {{cannot call value of non-function type 'E'}}
+    case B<Int>(): // expected-error {{cannot specialize a non-generic definition}} expected-note {{while parsing this '<' as a type parameter bracket}}
       break
     default:
       break;
@@ -25,13 +22,10 @@ enum E {
 
 func testE(e: E) {
   switch e {
-  case E.A<UndefinedTy>(): // expected-error {{cannot find type 'UndefinedTy' in scope}}
+  case E.A<UndefinedTy>(): // expected-error {{cannot specialize a non-generic definition}}
   // expected-note@-1 {{while parsing this '<' as a type parameter bracket}}
-  // expected-error@-2 {{cannot specialize non-generic type 'E'}}
-  // expected-error@-3 {{cannot call value of non-function type 'E'}}
     break
-  case E.B<Int>(): // expected-error {{cannot specialize non-generic type 'E'}}
-  // expected-error@-1 {{cannot call value of non-function type 'E'}}
+  case E.B<Int>(): // expected-error {{cannot specialize a non-generic definition}} expected-note {{while parsing this '<' as a type parameter bracket}}
     break
   case .C(): // expected-error {{pattern with associated values does not match enum case 'C'}}
              // expected-note@-1 {{remove associated values to make the pattern match}} {{10-12=}} 

test/Parse/generic_disambiguation.swift

@@ -26,21 +26,15 @@ var a, b, c, d : Int
 _ = a < b
 _ = (a < b, c > d)
 // Parses as generic because of lparen after '>'
-(a < b, c > (d)) // expected-error{{cannot find type 'b' in scope}}
-// expected-note@-1 2 {{while parsing this '<' as a type parameter bracket}}
-// expected-error@-2 {{cannot specialize non-generic type 'Int'}}
-// expected-error@-3 {{cannot call value of non-function type 'Int'}}
-// expected-error@-4 {{cannot find type 'c' in scope}}
+(a < b, c > (d)) // expected-error{{cannot specialize a non-generic definition}}
+// expected-note@-1 {{while parsing this '<' as a type parameter bracket}}
 // Parses as generic because of lparen after '>'
-(a<b, c>(d)) // expected-error{{cannot find type 'b' in scope}}
-// expected-note@-1 2 {{while parsing this '<' as a type parameter bracket}}
-// expected-error@-2 {{cannot specialize non-generic type 'Int'}}
-// expected-error@-3 {{cannot call value of non-function type 'Int'}}
-// expected-error@-4 {{cannot find type 'c' in scope}}
+(a<b, c>(d)) // expected-error{{cannot specialize a non-generic definition}}
+// expected-note@-1 {{while parsing this '<' as a type parameter bracket}}
 _ = a>(b)
 _ = a > (b)
 
-generic<Int>(0) // expected-error{{cannot explicitly specialize a generic function}}
+generic<Int>(0) // expected-error{{cannot explicitly specialize a generic function}} expected-note{{while parsing this '<' as a type parameter bracket}}
 
 A<B>.c()
 A<A<B>>.c()