Merge pull request swiftlang#19898 from xedin/initial-cs-after-solving

[ConstraintSystem] Make sure that system is returned into its original

Author: xedin

lib/Sema/CSSolver.cpp

@@ -406,6 +406,10 @@ ConstraintSystem::SolverState::SolverState(
   ++NumSolutionAttempts;
   SolutionAttempt = NumSolutionAttempts;
 
+  // Record active constraints for re-activation at the end of lifetime.
+  for (auto &constraint : cs.ActiveConstraints)
+    activeConstraints.push_back(&constraint);
+
   // If we're supposed to debug a specific constraint solver attempt,
   // turn on debugging now.
   ASTContext &ctx = CS.getTypeChecker().Context;
@@ -425,6 +429,34 @@ ConstraintSystem::SolverState::~SolverState() {
          "Expected constraint system to have this solver state!");
   CS.solverState = nullptr;
 
+  // Make sure that all of the retired constraints have been returned
+  // to constraint system.
+  assert(!hasRetiredConstraints());
+
+  // Make sure that all of the generated constraints have been handled.
+  assert(generatedConstraints.empty());
+
+  // Re-activate constraints which were initially marked as "active"
+  // to restore original state of the constraint system.
+  for (auto *constraint : activeConstraints) {
+    // If the constraint is already active we can just move on.
+    if (constraint->isActive())
+      continue;
+
+    // Make sure that constraint is present in the "inactive" set
+    // before transferring it to "active".
+    auto existing = llvm::find_if(CS.InactiveConstraints,
+                                  [&constraint](const Constraint &inactive) {
+                                    return &inactive == constraint;
+                                  });
+    assert(existing != CS.InactiveConstraints.end());
+
+    // Transfer the constraint to "active" set.
+    CS.InactiveConstraints.erase(existing);
+    CS.ActiveConstraints.push_back(constraint);
+    constraint->setActive(true);
+  }
+
   // Restore debugging state.
   LangOptions &langOpts = CS.getTypeChecker().Context.LangOpts;
   langOpts.DebugConstraintSolver = OldDebugConstraintSolver;
@@ -1230,6 +1262,17 @@ bool ConstraintSystem::solve(Expr *const expr,
 void ConstraintSystem::solve(SmallVectorImpl<Solution> &solutions) {
   assert(solverState);
 
+  // If constraint system failed while trying to
+  // genenerate constraints, let's stop right here.
+  if (failedConstraint)
+    return;
+
+  // Allocate new solver scope, so constraint system
+  // could be restored to its original state afterwards.
+  // Otherwise there is a risk that some of the constraints
+  // are not going to be re-introduced to the system.
+  SolverScope scope(*this);
+
   SmallVector<std::unique_ptr<SolverStep>, 16> workList;
   // First step is always wraps whole constraint system.
   workList.push_back(llvm::make_unique<SplitterStep>(*this, solutions));

lib/Sema/ConstraintSystem.cpp

@@ -2045,15 +2045,6 @@ bool ConstraintSystem::salvage(SmallVectorImpl<Solution> &viable, Expr *expr) {
     SolverState state(expr, *this, FreeTypeVariableBinding::Disallow);
     state.recordFixes = true;
 
-    // Retry all inactive and failed constraints
-    if (failedConstraint) {
-      addUnsolvedConstraint(failedConstraint);
-      failedConstraint = nullptr;
-    }
-    ActiveConstraints.splice(ActiveConstraints.end(), InactiveConstraints);
-    for (auto &constraint : ActiveConstraints)
-      constraint.setActive(true);
-
     // Solve the system.
     solve(viable);
 

lib/Sema/ConstraintSystem.h

@@ -1308,6 +1308,10 @@ class ConstraintSystem {
     /// are added back to the circulation.
     ConstraintList retiredConstraints;
 
+    /// The set of constraints which were active at the time of this state
+    /// creating, it's used to re-activate them on destruction.
+    SmallVector<Constraint *, 4> activeConstraints;
+
     /// The current set of generated constraints.
     SmallVector<Constraint *, 4> generatedConstraints;
 

validation-test/Sema/type_checker_perf/fast/more_specialized_generic_func.swift.gyb

@@ -1,4 +1,4 @@
-// RUN: %scale-test --begin 1 --end 10 --step 1 --select incrementScopeCounter %s --expected-exit-code 0
+// RUN: %scale-test --begin 8 --end 40 --step 2 --select incrementScopeCounter %s --expected-exit-code 0
 // REQUIRES: OS=macosx
 // REQUIRES: asserts