Merge pull request swiftlang#14581 from rudkx/remove-constraint-propagation

[ConstraintSystem] Remove constraint propagation.

Author: rudkx

include/swift/Basic/LangOptions.h

@@ -157,10 +157,6 @@ namespace swift {
     /// solver should be debugged.
     unsigned DebugConstraintSolverAttempt = 0;
 
-    /// \brief Enable the experimental constraint propagation in the
-    /// type checker.
-    bool EnableConstraintPropagation = false;
-
     /// \brief Enable the iterative type checker.
     bool IterativeTypeChecker = false;
 

include/swift/Option/FrontendOptions.td

@@ -151,9 +151,6 @@ def debug_constraints : Flag<["-"], "debug-constraints">,
 def debug_constraints_attempt : Separate<["-"], "debug-constraints-attempt">,
   HelpText<"Debug the constraint solver at a given attempt">;
 
-def propagate_constraints : Flag<["-"], "propagate-constraints">,
-  HelpText<"Enable constraint propagation in the type checker">;
-
 def iterative_type_checker : Flag<["-"], "iterative-type-checker">,
   HelpText<"Enable the iterative type checker">;
 

lib/Frontend/CompilerInvocation.cpp

@@ -208,7 +208,6 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
 
   Opts.EnableASTScopeLookup |= Args.hasArg(OPT_enable_astscope_lookup);
   Opts.DebugConstraintSolver |= Args.hasArg(OPT_debug_constraints);
-  Opts.EnableConstraintPropagation |= Args.hasArg(OPT_propagate_constraints);
   Opts.IterativeTypeChecker |= Args.hasArg(OPT_iterative_type_checker);
   Opts.NamedLazyMemberLoading &= !Args.hasArg(OPT_disable_named_lazy_member_loading);
   Opts.DebugGenericSignatures |= Args.hasArg(OPT_debug_generic_signatures);

lib/Sema/CMakeLists.txt

@@ -8,7 +8,6 @@ add_swift_library(swiftSema STATIC
   CSBindings.cpp
   CSDiag.cpp
   CSGen.cpp
-  CSPropagate.cpp
   CSRanking.cpp
   CSSimplify.cpp
   CSSolver.cpp

lib/Sema/CSPropagate.cpp

@@ -984,12 +984,6 @@ 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,
@@ -1421,11 +1415,6 @@ bool ConstraintSystem::solve(Expr *const expr,
   if (failedConstraint || 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);