RequirementMachine: Tri-state enable flag, and move queries to GenericSignatureQueries.cpp

The -enable-requirement-machine and -disable-requirement-machine flags are now
replaced by a new flag -requirement-machine={on,off,verify}.

Author: slavapestov

include/swift/Basic/LangOptions.h

@@ -78,6 +78,18 @@ namespace swift {
     ErrorOnFailureRemarkOnSuccess
   };
 
+  /// Value for LangOptions::EnableRequirementMachine.
+  enum class RequirementMachineMode {
+    /// Use the GenericSignatureBuilder for all queries.
+    Disabled = 0,
+
+    /// Use the RequirementMachine for all queries.
+    Enabled = 1,
+
+    /// Use both and assert if the results do not match.
+    Verify = 2
+  };
+
   /// A collection of options that affect the language dialect and
   /// provide compiler debugging facilities.
   class LangOptions final {
@@ -446,7 +458,8 @@ namespace swift {
         ASTVerifierOverrideKind::NoOverride;
 
     /// Whether the new experimental generics implementation is enabled.
-    bool EnableRequirementMachine = false;
+    RequirementMachineMode EnableRequirementMachine =
+        RequirementMachineMode::Disabled;
 
     /// Enables debugging output from the requirement machine.
     bool DebugRequirementMachine = false;

include/swift/Option/FrontendOptions.td

@@ -277,11 +277,8 @@ def debug_constraints_on_line_EQ : Joined<["-"], "debug-constraints-on-line=">,
 def disable_named_lazy_member_loading : Flag<["-"], "disable-named-lazy-member-loading">,
   HelpText<"Disable per-name lazy member loading">;
 
-def enable_requirement_machine : Flag<["-"], "enable-requirement-machine">,
-  HelpText<"Enable experimental generics implementation">;
-
-def disable_requirement_machine : Flag<["-"], "disable-requirement-machine">,
-  HelpText<"Disable experimental generics implementation">;
+def requirement_machine_EQ : Joined<["-"], "requirement-machine=">,
+  HelpText<"Control usage of experimental generics implementation: 'on', 'off', or 'verify'">;
 
 def debug_requirement_machine : Flag<["-"], "debug-requirement-machine">,
   HelpText<"Enables debugging output from the generics implementation">;

lib/AST/CMakeLists.txt

@@ -74,6 +74,7 @@ add_swift_host_library(swiftAST STATIC
   RawComment.cpp
   RequirementEnvironment.cpp
   RequirementMachine/EquivalenceClassMap.cpp
+  RequirementMachine/GenericSignatureQueries.cpp
   RequirementMachine/ProtocolGraph.cpp
   RequirementMachine/RequirementMachine.cpp
   RequirementMachine/RewriteContext.cpp