[ConstraintSystem] Rename solveIteratively to solve and start using it

Remove solution filtering from new iterative `solve` method, and
replace all usages of `solveRec` with it.

Author: xedin

lib/Sema/CSSolver.cpp

@@ -686,10 +686,9 @@ bool ConstraintSystem::Candidate::solve(
   {
     SolverState state(E, cs, FreeTypeVariableBinding::Allow);
 
-    // Use solveRec() instead of solve() in here, because solve()
-    // would try to deduce the best solution, which we don't
-    // really want. Instead, we want the reduced set of domain choices.
-    cs.solveRec(solutions);
+    // Use solve which doesn't try to filter solution list.
+    // Because we want the whole set of possible domain choices.
+    cs.solve(solutions);
   }
 
   if (TC.getLangOpts().DebugConstraintSolver) {
@@ -1276,7 +1275,7 @@ bool ConstraintSystem::solve(Expr *const expr,
   SolverState state(expr, *this, allowFreeTypeVariables);
 
   // Solve the system.
-  solveRec(solutions);
+  solve(solutions);
 
   if (TC.getLangOpts().DebugConstraintSolver) {
     auto &log = getASTContext().TypeCheckerDebug->getStream();
@@ -1557,10 +1556,8 @@ bool ConstraintSystem::solveRec(SmallVectorImpl<Solution> &solutions) {
   return !anySolutions;
 }
 
-bool ConstraintSystem::solveIteratively(
-    Expr *expr, SmallVectorImpl<Solution> &solutions,
-    FreeTypeVariableBinding allowFreeTypeVariables) {
-  SolverState state(expr, *this, allowFreeTypeVariables);
+void ConstraintSystem::solve(SmallVectorImpl<Solution> &solutions) {
+  assert(solverState);
 
   SmallVector<SolverStep *, 16> workList;
   // First step is always wraps whole constraint system.
@@ -1640,15 +1637,6 @@ bool ConstraintSystem::solveIteratively(
       result.transfer(workList);
     }
   }
-
-  // Filter deduced solutions, try to figure out if there is
-  // a single best solution to use, if not explicitly disabled
-  // by constraint system options.
-  if (!retainAllSolutions())
-    filterSolutions(solutions, state.ExprWeights);
-
-  // We fail if there is no solution or the expression was too complex.
-  return solutions.empty() || getExpressionTooComplex(solutions);
 }
 
 /// Whether we should short-circuit a disjunction that already has a

lib/Sema/ConstraintSystem.cpp

@@ -2072,7 +2072,7 @@ bool ConstraintSystem::salvage(SmallVectorImpl<Solution> &viable, Expr *expr) {
     state.recordFixes = true;
 
     // Solve the system.
-    solveRec(viable);
+    solve(viable);
 
     // Check whether we have a best solution; this can happen if we found
     // a series of fixes that worked.

lib/Sema/ConstraintSystem.h

@@ -3100,9 +3100,6 @@ class ConstraintSystem {
   /// \returns true if there are no solutions
   bool solveRec(SmallVectorImpl<Solution> &solutions);
 
-  bool solveIteratively(Expr *expr, SmallVectorImpl<Solution> &solutions,
-                        FreeTypeVariableBinding allowFreeTypeVariables);
-
   /// \brief Solve the system of constraints.
   ///
   /// \param allowFreeTypeVariables How to bind free type variables in
@@ -3114,6 +3111,14 @@ class ConstraintSystem {
                                     = FreeTypeVariableBinding::Disallow);
 
 private:
+  /// \brief Solve the system of constraints.
+  ///
+  /// This method responsible for running search/solver algorithm.
+  /// It doesn't filter solutions, that's the job of top-level `solve` methods.
+  ///
+  /// \param solutions The set of solutions to this system of constraints.
+  void solve(SmallVectorImpl<Solution> &solutions);
+
   /// \brief Compare two solutions to the same set of constraints.
   ///
   /// \param cs The constraint system.

test/Constraints/closures.swift

@@ -497,8 +497,8 @@ sr3520_1 { $0 = 1 } // expected-error {{cannot convert value of type '()' to clo
 struct S_3520 {
   var number1: Int
 }
-func sr3520_set_via_closure<S, T>(_ closure: (inout S, T) -> ()) {}
-sr3520_set_via_closure({ $0.number1 = $1 }) // expected-error {{type of expression is ambiguous without more context}}
+func sr3520_set_via_closure<S, T>(_ closure: (inout S, T) -> ()) {} // expected-note {{in call to function 'sr3520_set_via_closure'}}
+sr3520_set_via_closure({ $0.number1 = $1 }) // expected-error {{generic parameter 'S' could not be inferred}}
 
 // SR-3073: UnresolvedDotExpr in single expression closure