[Constraint solver] Remove ExprTypeCheckListener::preCheckFailed().

Failures will be reported to clients; this callback is unnecessary.

Author: DougGregor

lib/Sema/TypeCheckConstraints.cpp

@@ -2035,7 +2035,6 @@ Expr *ExprTypeCheckListener::appliedSolution(Solution &solution, Expr *expr) {
   return expr;
 }
 
-void ExprTypeCheckListener::preCheckFailed(Expr *expr) {}
 void ExprTypeCheckListener::applySolutionFailed(Solution &solution,
                                                 Expr *expr) {}
 
@@ -2097,12 +2096,6 @@ class FallbackDiagnosticListener : public ExprTypeCheckListener {
     return BaseListener ? BaseListener->appliedSolution(solution, expr) : expr;
   }
 
-  void preCheckFailed(Expr *expr) override {
-    if (BaseListener)
-      BaseListener->preCheckFailed(expr);
-    maybeProduceFallbackDiagnostic(expr);
-  }
-
   void applySolutionFailed(Solution &solution, Expr *expr) override {
     if (BaseListener)
       BaseListener->applySolutionFailed(solution, expr);
@@ -2169,7 +2162,6 @@ Type TypeChecker::typeCheckExpressionImpl(Expr *&expr, DeclContext *dc,
   // First, pre-check the expression, validating any types that occur in the
   // expression and folding sequence expressions.
   if (ConstraintSystem::preCheckExpression(expr, dc, baseCS)) {
-    listener.preCheckFailed(expr);
     return Type();
   }
 

lib/Sema/TypeChecker.h

@@ -321,10 +321,6 @@ class ExprTypeCheckListener {
   virtual Expr *appliedSolution(constraints::Solution &solution,
                                 Expr *expr);
 
-  /// Callback invoked if expression is structurally unsound and can't
-  /// be correctly processed by the constraint solver.
-  virtual void preCheckFailed(Expr *expr);
-
   /// Callback invoked if application of chosen solution to
   /// expression has failed.
   virtual void applySolutionFailed(constraints::Solution &solution, Expr *expr);