Sema: Remove ConstraintSystemPhase::{Diagnostics,Finalization}

Author: slavapestov

include/swift/Sema/ConstraintSystem.h

@@ -2131,9 +2131,7 @@ class SyntacticElementTargetRewriter {
 
 enum class ConstraintSystemPhase {
   ConstraintGeneration,
-  Solving,
-  Diagnostics,
-  Finalization
+  Solving
 };
 
 /// Retrieve the closure type from the constraint system.
@@ -2693,18 +2691,7 @@ class ConstraintSystem {
     case ConstraintSystemPhase::Solving:
       // We can come back to constraint generation phase while
       // processing result builder body.
-      assert(newPhase == ConstraintSystemPhase::ConstraintGeneration ||
-             newPhase == ConstraintSystemPhase::Diagnostics ||
-             newPhase == ConstraintSystemPhase::Finalization);
-      break;
-
-    case ConstraintSystemPhase::Diagnostics:
-      assert(newPhase == ConstraintSystemPhase::Solving ||
-             newPhase == ConstraintSystemPhase::Finalization);
-      break;
-
-    case ConstraintSystemPhase::Finalization:
-      assert(newPhase == ConstraintSystemPhase::Diagnostics);
+      assert(newPhase == ConstraintSystemPhase::ConstraintGeneration);
       break;
     }
 #endif

lib/Sema/CSSolver.cpp

@@ -1579,8 +1579,6 @@ void ConstraintSystem::solveImpl(SmallVectorImpl<Solution> &solutions) {
 
   setPhase(ConstraintSystemPhase::Solving);
 
-  SWIFT_DEFER { setPhase(ConstraintSystemPhase::Finalization); };
-
   // If constraint system failed while trying to
   // genenerate constraints, let's stop right here.
   if (failedConstraint)

lib/Sema/ConstraintSystem.cpp

@@ -2098,8 +2098,6 @@ SolutionResult ConstraintSystem::salvage() {
     llvm::errs() << "---Attempting to salvage and emit diagnostics---\n";
   }
 
-  setPhase(ConstraintSystemPhase::Diagnostics);
-
   // Attempt to solve again, capturing all states that come from our attempts to
   // select overloads or bind type variables.
   //
@@ -4797,10 +4795,6 @@ void SyntacticElementTargetKey::dump(raw_ostream &OS) const {
 /// This is guaranteed to always emit an error message.
 ///
 void ConstraintSystem::diagnoseFailureFor(SyntacticElementTarget target) {
-  setPhase(ConstraintSystemPhase::Diagnostics);
-
-  SWIFT_DEFER { setPhase(ConstraintSystemPhase::Finalization); };
-
   auto &DE = getASTContext().Diags;
 
   // If constraint system is in invalid state always produce