Merge pull request #8262 from rudkx/propagate-constraints

Author: swift-ci

lib/Sema/CSGen.cpp

@@ -3064,10 +3064,6 @@ Expr *ConstraintSystem::generateConstraints(Expr *expr) {
   if (result)
     this->optimizeConstraints(result);
 
-  // If the experimental constraint propagation pass is enabled, run it.
-  if (TC.Context.LangOpts.EnableConstraintPropagation)
-    propagateConstraints();
-
   return result;
 }
 

lib/Sema/CSPropagate.cpp

@@ -16,10 +16,12 @@
 #include "ConstraintGraph.h"
 #include "ConstraintSystem.h"
 #include "llvm/ADT/DenseSet.h"
-#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 using namespace swift;
 using namespace constraints;
 
-void ConstraintSystem::propagateConstraints() {
+bool ConstraintSystem::propagateConstraints() {
+  assert(getActiveConstraints().empty() && "Expected no active constraints!");
+
+  return false;
 }

lib/Sema/CSSimplify.cpp

@@ -745,10 +745,8 @@ matchCallArguments(ConstraintSystem &cs, ConstraintKind kind,
       if (!haveOneNonUserConversion) {
         subflags |= ConstraintSystem::TMF_ApplyingOperatorParameter;
       }
-      
-      switch (cs.matchTypes(argTy,paramTy,
-                            subKind, subflags,
-                            loc)) {
+
+      switch (cs.matchTypes(argTy, paramTy, subKind, subflags, loc)) {
       case ConstraintSystem::SolutionKind::Error:
         return ConstraintSystem::SolutionKind::Error;
 

lib/Sema/CSSolver.cpp

@@ -1579,6 +1579,12 @@ void ConstraintSystem::Candidate::applySolutions(
 }
 
 void ConstraintSystem::shrink(Expr *expr) {
+  // Disable the shrink pass when constraint propagation is
+  // enabled. They achieve similar effects, and the shrink pass is
+  // known to have bad behavior in some cases.
+  if (TC.Context.LangOpts.EnableConstraintPropagation)
+    return;
+
   typedef llvm::SmallDenseMap<Expr *, ArrayRef<ValueDecl *>> DomainMap;
 
   // A collection of original domains of all of the expressions,
@@ -1977,6 +1983,17 @@ bool ConstraintSystem::solve(SmallVectorImpl<Solution> &solutions,
   // Set up solver state.
   SolverState state(*this);
 
+  // Simplify any constraints left active after constraint generation
+  // and optimization. Return if the resulting system has no
+  // solutions.
+  if (simplify())
+    return true;
+
+  // If the experimental constraint propagation pass is enabled, run it.
+  if (TC.Context.LangOpts.EnableConstraintPropagation)
+    if (propagateConstraints())
+      return true;
+
   // Solve the system.
   solveRec(solutions, allowFreeTypeVariables);
 
@@ -2322,7 +2339,7 @@ void ConstraintSystem::collectDisjunctions(
   }
 }
 
-std::pair<PotentialBindings, TypeVariableType *>
+static std::pair<PotentialBindings, TypeVariableType *>
 determineBestBindings(ConstraintSystem &CS) {
   // Look for potential type variable bindings.
   TypeVariableType *bestTypeVar = nullptr;

lib/Sema/ConstraintSystem.h

@@ -2054,7 +2054,10 @@ class ConstraintSystem {
 
   /// \brief Propagate constraints in an effort to enforce local
   /// consistency to reduce the time to solve the system.
-  void propagateConstraints();
+  ///
+  /// \returns true if the system is known to be inconsistent (have no
+  /// solutions).
+  bool propagateConstraints();
 
   /// \brief The result of attempting to resolve a constraint or set of
   /// constraints.