[CSBindings] Prevent binding printing if it not a part of an initial state in ComponentStep or does not contribute to or result from a changed state in TypeVariableStep.

Author: Amritpan Kaur

include/swift/Sema/ConstraintSystem.h

@@ -5346,7 +5346,12 @@ class ConstraintSystem {
       Type wrapperType, Type paramType, ParamDecl *param, Identifier argLabel,
       ConstraintKind matchKind, ConstraintLocatorBuilder locator);
 
-  Optional<BindingSet> determineBestBindings();
+  /// Determine whether given type variable with its set of bindings is viable
+  /// to be attempted on the next step of the solver.
+  ///
+  /// \c isSingle indicates whether this is the only component produced
+  /// by "split" step, in which case bindings should not be printed in debug output.
+  Optional<BindingSet> determineBestBindings(bool isSingle = false);
 
   /// Get bindings for the given type variable based on current
   /// state of the constraint system.

lib/Sema/CSBindings.cpp

@@ -735,7 +735,7 @@ BindingSet::BindingScore BindingSet::formBindingScore(const BindingSet &b) {
                          -numNonDefaultableBindings);
 }
 
-Optional<BindingSet> ConstraintSystem::determineBestBindings() {
+Optional<BindingSet> ConstraintSystem::determineBestBindings(bool isSingle) {
   // Look for potential type variable bindings.
   Optional<BindingSet> bestBindings;
   llvm::SmallDenseMap<TypeVariableType *, BindingSet> cache;
@@ -798,7 +798,11 @@ Optional<BindingSet> ConstraintSystem::determineBestBindings() {
       continue;
 
     if (isDebugMode()) {
-      bindings.dump(typeVar, llvm::errs(), solverState->depth * 2);
+      if (!isSingle) {
+        bindings.dump(typeVar, llvm::errs(), solverState->depth * 2 + 2);
+      } else if (isSingle && !bindings.Bindings.empty()) {
+        bindings.dump(typeVar, llvm::errs(), solverState->depth * 2 + 4);
+      }
     }
 
     // If these are the first bindings, or they are better than what

lib/Sema/CSStep.cpp

@@ -342,7 +342,7 @@ StepResult ComponentStep::take(bool prevFailed) {
 
   /// Try to figure out what this step is going to be,
   /// after the scope has been established.
-  auto bestBindings = CS.determineBestBindings();
+  auto bestBindings = CS.determineBestBindings(IsSingle);
   auto *disjunction = CS.selectDisjunction();
   auto *conjunction = CS.selectConjunction();