Merge pull request #40459 from slavapestov/rqm-disabled-merged-types

RequirementMachine: Add flags to enable and disable merged associated types

Author: slavapestov

include/swift/Basic/LangOptions.h

@@ -468,6 +468,9 @@ namespace swift {
     RequirementMachineMode EnableRequirementMachine =
         RequirementMachineMode::Enabled;
 
+    /// Enables merged associated type support, which might go away.
+    bool RequirementMachineMergedAssociatedTypes = true;
+
     /// Enables dumping rewrite systems from the requirement machine.
     bool DumpRequirementMachine = false;
 

include/swift/Option/FrontendOptions.td

@@ -325,6 +325,14 @@ def requirement_machine_depth_limit : Separate<["-"], "requirement-machine-depth
   Flags<[FrontendOption, HelpHidden, DoesNotAffectIncrementalBuild]>,
   HelpText<"Set the maximum depth before we give up on confluent completion">;
 
+def disable_requirement_machine_merged_associated_types : Flag<["-"], "disable-requirement-machine-merged-associated-types">,
+  Flags<[FrontendOption, HelpHidden, DoesNotAffectIncrementalBuild]>,
+  HelpText<"Disable merged associated types">;
+
+def enable_requirement_machine_merged_associated_types : Flag<["-"], "enable-requirement-machine-merged-associated-types">,
+  Flags<[FrontendOption, HelpHidden, DoesNotAffectIncrementalBuild]>,
+  HelpText<"Enable merged associated types">;
+
 def debug_generic_signatures : Flag<["-"], "debug-generic-signatures">,
   HelpText<"Debug generic signatures">;
 

lib/AST/RequirementMachine/KnuthBendix.cpp

@@ -294,7 +294,8 @@ void RewriteSystem::processMergedAssociatedTypes() {
 /// types in RewriteSystem::processMergedAssociatedTypes().
 void RewriteSystem::checkMergedAssociatedType(Term lhs, Term rhs) {
   // FIXME: Figure out 3-cell representation for merged associated types
-  if (RecordLoops)
+  if (RecordLoops ||
+      !Context.getASTContext().LangOpts.RequirementMachineMergedAssociatedTypes)
     return;
 
   if (lhs.size() == rhs.size() &&

lib/Frontend/CompilerInvocation.cpp

@@ -891,6 +891,12 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
                      A->getAsString(Args), A->getValue());
   }
 
+  if (auto A = Args.getLastArg(OPT_enable_requirement_machine_merged_associated_types,
+                               OPT_disable_requirement_machine_merged_associated_types)) {
+    Opts.RequirementMachineMergedAssociatedTypes
+      = A->getOption().matches(OPT_enable_requirement_machine_merged_associated_types);
+  }
+
   Opts.DumpRequirementMachine = Args.hasArg(
       OPT_dump_requirement_machine);
   Opts.AnalyzeRequirementMachine = Args.hasArg(