[CSStep] Allocate component scopes only if siblings didn't fail

If sibling components failed, there is no reason to establish new
scope since remaining containers are not really going to be taken
but fail fast instead.

Author: xedin

lib/Sema/CSStep.cpp

@@ -253,6 +253,9 @@ StepResult ComponentStep::take(bool prevFailed) {
   if (prevFailed || CS.getExpressionTooComplex(Solutions))
     return done(/*isSuccess=*/false);
 
+  // Setup active scope, only if previous component didn't fail.
+  setupScope();
+
   /// Try to figure out what this step is going to be,
   /// after the scope has been established.
   auto *disjunction = CS.selectDisjunction();

lib/Sema/CSStep.h

@@ -373,7 +373,18 @@ class ComponentStep final : public SolverStep {
     OrphanedConstraint = constraint;
   }
 
-  void setup() override {
+  StepResult take(bool prevFailed) override;
+  StepResult resume(bool prevFailed) override;
+
+  // The number of disjunction constraints associated with this component.
+  unsigned disjunctionCount() const { return NumDisjunctions; }
+
+  void print(llvm::raw_ostream &Out) override {
+    Out << "ComponentStep with at #" << Index << '\n';
+  }
+
+private:
+  void setupScope() {
     // If this is a single component, there is no need
     // to preliminary modify constraint system or log anything.
     if (IsSingle)
@@ -387,16 +398,6 @@ class ComponentStep final : public SolverStep {
     // let's return it ot the graph.
     CS.CG.setOrphanedConstraint(OrphanedConstraint);
   }
-
-  StepResult take(bool prevFailed) override;
-  StepResult resume(bool prevFailed) override;
-
-  // The number of disjunction constraints associated with this component.
-  unsigned disjunctionCount() const { return NumDisjunctions; }
-
-  void print(llvm::raw_ostream &Out) override {
-    Out << "ComponentStep with at #" << Index << '\n';
-  }
 };
 
 template <typename P> class BindingStep : public SolverStep {