RequirementMachine: Add a mode allowing unresolved name symbols in rewrite rules

Author: slavapestov

lib/AST/RequirementMachine/RequirementMachine.cpp

@@ -371,7 +371,7 @@ void RequirementMachine::addGenericSignature(CanGenericSignature sig) {
                     std::move(builder.RequirementRules),
                     std::move(builder.Protocols));
 
-  computeCompletion();
+  computeCompletion(RewriteSystem::DisallowInvalidRequirements);
 
   if (Dump) {
     llvm::dbgs() << "}\n";
@@ -380,7 +380,7 @@ void RequirementMachine::addGenericSignature(CanGenericSignature sig) {
 
 /// Attempt to obtain a confluent rewrite system using the completion
 /// procedure.
-void RequirementMachine::computeCompletion() {
+void RequirementMachine::computeCompletion(RewriteSystem::ValidityPolicy policy) {
   while (true) {
     // First, run the Knuth-Bendix algorithm to resolve overlapping rules.
     auto result = System.computeConfluentCompletion(
@@ -415,7 +415,7 @@ void RequirementMachine::computeCompletion() {
     checkCompletionResult();
 
     // Check invariants.
-    System.verifyRewriteRules();
+    System.verifyRewriteRules(policy);
     System.verifyHomotopyGenerators();
 
     // Build the property map, which also performs concrete term

lib/AST/RequirementMachine/RequirementMachine.h

@@ -80,7 +80,8 @@ class RequirementMachine final {
   void addGenericSignature(CanGenericSignature sig);
 
   bool isComplete() const;
-  void computeCompletion();
+
+  void computeCompletion(RewriteSystem::ValidityPolicy policy);
 
   MutableTerm getLongestValidPrefix(const MutableTerm &term) const;
 

lib/AST/RequirementMachine/RewriteSystem.cpp

@@ -358,7 +358,7 @@ void RewriteSystem::simplifyRewriteSystem() {
   }
 }
 
-void RewriteSystem::verifyRewriteRules() const {
+void RewriteSystem::verifyRewriteRules(ValidityPolicy policy) const {
 #ifndef NDEBUG
 
 #define ASSERT_RULE(expr) \
@@ -396,10 +396,12 @@ void RewriteSystem::verifyRewriteRules() const {
     for (unsigned index : indices(rhs)) {
       auto symbol = rhs[index];
 
-      // FIXME: This is only true if the input requirements were valid.
-      // On invalid code, we'll need to skip this assertion (and instead
-      // assert that we diagnosed an error!)
-      ASSERT_RULE(symbol.getKind() != Symbol::Kind::Name);
+      // This is only true if the input requirements were valid.
+      if (policy == DisallowInvalidRequirements) {
+        ASSERT_RULE(symbol.getKind() != Symbol::Kind::Name);
+      } else {
+        // FIXME: Assert that we diagnosed an error
+      }
 
       ASSERT_RULE(symbol.getKind() != Symbol::Kind::Layout);
       ASSERT_RULE(!symbol.isSuperclassOrConcreteType());

lib/AST/RequirementMachine/RewriteSystem.h

@@ -406,7 +406,12 @@ class RewriteSystem final {
 
   void minimizeRewriteSystem();
 
-  void verifyRewriteRules() const;
+  enum ValidityPolicy {
+    AllowInvalidRequirements,
+    DisallowInvalidRequirements
+  };
+
+  void verifyRewriteRules(ValidityPolicy policy) const;
 
   void verifyHomotopyGenerators() const;