[Diagnostics] Remove the now-unused AllowInvalidUseOfTrailingClosure

Diagnosis for invalid uses of trailing closures has been folded in
with argument-matching diagnostics, so remove all of the machinery
around the syntactic "mismatched trailing closure" logic.

Author: DougGregor

lib/Sema/CSDiagnostics.cpp

@@ -5905,19 +5905,6 @@ bool ExtraneousCallFailure::diagnoseAsError() {
   return true;
 }
 
-bool InvalidUseOfTrailingClosure::diagnoseAsError() {
-  emitDiagnostic(diag::trailing_closure_bad_param, getToType())
-      .highlight(getSourceRange());
-
-  if (auto overload = getCalleeOverloadChoiceIfAvailable(getLocator())) {
-    if (auto *decl = overload->choice.getDeclOrNull()) {
-      emitDiagnosticAt(decl, diag::decl_declared_here, decl->getName());
-    }
-  }
-
-  return true;
-}
-
 void NonEphemeralConversionFailure::emitSuggestionNotes() const {
   auto getPointerKind = [](Type ty) -> PointerTypeKind {
     PointerTypeKind pointerKind;

lib/Sema/CSFix.cpp

@@ -1187,21 +1187,6 @@ RemoveInvalidCall *RemoveInvalidCall::create(ConstraintSystem &cs,
   return new (cs.getAllocator()) RemoveInvalidCall(cs, locator);
 }
 
-bool AllowInvalidUseOfTrailingClosure::diagnose(const Solution &solution,
-                                                bool asNote) const {
-  InvalidUseOfTrailingClosure failure(solution, getFromType(), getToType(),
-                                      getLocator());
-  return failure.diagnose(asNote);
-}
-
-AllowInvalidUseOfTrailingClosure *
-AllowInvalidUseOfTrailingClosure::create(ConstraintSystem &cs, Type argType,
-                                         Type paramType,
-                                         ConstraintLocator *locator) {
-  return new (cs.getAllocator())
-      AllowInvalidUseOfTrailingClosure(cs, argType, paramType, locator);
-}
-
 bool TreatEphemeralAsNonEphemeral::diagnose(const Solution &solution,
                                             bool asNote) const {
   NonEphemeralConversionFailure failure(solution, getLocator(), getFromType(),

lib/Sema/CSFix.h

@@ -222,8 +222,6 @@ enum class FixKind : uint8_t {
   /// a variable, a property etc.
   RemoveCall,
 
-  AllowInvalidUseOfTrailingClosure,
-
   /// Allow an ephemeral argument conversion for a parameter marked as being
   /// non-ephemeral.
   TreatEphemeralAsNonEphemeral,
@@ -1656,24 +1654,6 @@ class RemoveInvalidCall final : public ConstraintFix {
                                    ConstraintLocator *locator);
 };
 
-class AllowInvalidUseOfTrailingClosure final : public AllowArgumentMismatch {
-  AllowInvalidUseOfTrailingClosure(ConstraintSystem &cs, Type argType,
-                                   Type paramType, ConstraintLocator *locator)
-      : AllowArgumentMismatch(cs, FixKind::AllowInvalidUseOfTrailingClosure,
-                              argType, paramType, locator) {}
-
-public:
-  std::string getName() const {
-    return "allow invalid use of trailing closure";
-  }
-
-  bool diagnose(const Solution &solution, bool asNote = false) const;
-
-  static AllowInvalidUseOfTrailingClosure *create(ConstraintSystem &cs,
-                                                  Type argType, Type paramType,
-                                                  ConstraintLocator *locator);
-};
-
 class TreatEphemeralAsNonEphemeral final : public AllowArgumentMismatch {
   ConversionRestrictionKind ConversionKind;
 

lib/Sema/CSSimplify.cpp

@@ -60,11 +60,6 @@ bool MatchCallArgumentListener::relabelArguments(ArrayRef<Identifier> newNames){
   return true;
 }
 
-bool MatchCallArgumentListener::trailingClosureMismatch(
-    unsigned paramIdx, unsigned argIdx) {
-  return true;
-}
-
 /// Produce a score (smaller is better) comparing a parameter name and
 /// potentially-typo'd argument name.
 ///
@@ -949,37 +944,6 @@ class ArgumentFailureTracker : public MatchCallArgumentListener {
     return CS.recordFix(fix, impact);
   }
 
-  bool trailingClosureMismatch(unsigned paramIdx, unsigned argIdx) override {
-    if (!CS.shouldAttemptFixes())
-      return true;
-
-    const auto &param = Parameters[paramIdx];
-
-    auto *argLoc = CS.getConstraintLocator(
-        Locator.withPathElement(LocatorPathElt::ApplyArgToParam(
-            argIdx, paramIdx, param.getParameterFlags())));
-
-    // TODO(diagnostics): This fix should be attempted later
-    // when the argument is matched to a parameter. Doing that
-    // would not require special handling of the closure type.
-    Type argType;
-    if (auto *closure =
-            dyn_cast<ClosureExpr>(simplifyLocatorToAnchor(argLoc))) {
-      argType = CS.getClosureType(closure);
-    } else {
-      argType = Arguments[argIdx].getPlainType();
-    }
-
-    argType.visit([&](Type type) {
-      if (auto *typeVar = type->getAs<TypeVariableType>())
-        CS.recordPotentialHole(typeVar);
-    });
-
-    auto *fix = AllowInvalidUseOfTrailingClosure::create(
-        CS, argType, param.getPlainType(), argLoc);
-    return CS.recordFix(fix, /*impact=*/3);
-  }
-
   ArrayRef<std::pair<unsigned, AnyFunctionType::Param>>
   getExtraneousArguments() const {
     return ExtraArguments;
@@ -3351,9 +3315,6 @@ bool ConstraintSystem::repairFailures(
   case ConstraintLocator::ApplyArgToParam: {
     auto loc = getConstraintLocator(locator);
 
-    if (hasFixFor(loc, FixKind::AllowInvalidUseOfTrailingClosure))
-      return true;
-
     // Don't attempt to fix an argument being passed to a
     // _OptionalNilComparisonType parameter. Such an overload should only take
     // effect when a nil literal is used in valid code, and doesn't offer any
@@ -9601,7 +9562,6 @@ ConstraintSystem::SolutionKind ConstraintSystem::simplifyFixConstraint(
   case FixKind::GenericArgumentsMismatch:
   case FixKind::AllowMutatingMemberOnRValueBase:
   case FixKind::AllowTupleSplatForSingleParameter:
-  case FixKind::AllowInvalidUseOfTrailingClosure:
   case FixKind::AllowNonClassTypeToConvertToAnyObject:
   case FixKind::SpecifyClosureParameterType:
   case FixKind::SpecifyClosureReturnType:

lib/Sema/ConstraintSystem.h

@@ -4907,13 +4907,6 @@ class MatchCallArgumentListener {
   /// \returns true to indicate that this should cause a failure, false
   /// otherwise.
   virtual bool relabelArguments(ArrayRef<Identifier> newNames);
-
-  /// Indicates that the trailing closure argument at the given \c argIdx
-  /// cannot be passed to the last parameter at \c paramIdx.
-  ///
-  /// \returns true to indicate that this should cause a failure, false
-  /// otherwise.
-  virtual bool trailingClosureMismatch(unsigned paramIdx, unsigned argIdx);
 };
 
 /// Match the call arguments (as described by the given argument type) to