RequirementMachine: Correctly handle importing of protocols in inferConditionalRequirements()

This fixes a regression from the rule sharing implementation; I forgot
to handle the imported rules in builder.ImportedRules here.

This makes the usage of RuleBuilder in conditional requirement
inference look like the other usages of RuleBuilder, except
that the results are passed to RewriteSystem::addRules() instead
of RewriteSystem::initialize().

Author: slavapestov

lib/AST/RequirementMachine/ConcreteTypeWitness.cpp

@@ -531,8 +531,8 @@ void PropertyMap::inferConditionalRequirements(
     return;
 
   SmallVector<Requirement, 2> desugaredRequirements;
-  // FIXME: Store errors in the rewrite system to be diagnosed
-  // from the top-level generic signature requests.
+
+  // FIXME: Do we need to diagnose these errors?
   SmallVector<RequirementError, 2> errors;
 
   // First, desugar all conditional requirements.
@@ -547,47 +547,17 @@ void PropertyMap::inferConditionalRequirements(
   }
 
   // Now, convert desugared conditional requirements to rules.
-  for (auto req : desugaredRequirements) {
-    if (Debug.contains(DebugFlags::ConditionalRequirements)) {
-      llvm::dbgs() << "@@@ Desugared requirement: ";
-      req.dump(llvm::dbgs());
-      llvm::dbgs() << "\n";
-    }
 
-    if (req.getKind() == RequirementKind::Conformance) {
-      auto *proto = req.getProtocolDecl();
+  // This will update System.getReferencedProtocols() with any new
+  // protocols that were imported.
+  RuleBuilder builder(Context, System.getReferencedProtocols());
+  builder.initWithConditionalRequirements(desugaredRequirements,
+                                          substitutions);
 
-      // If we haven't seen this protocol before, add rules for its
-      // requirements.
-      if (!System.isKnownProtocol(proto)) {
-        if (Debug.contains(DebugFlags::ConditionalRequirements)) {
-          llvm::dbgs() << "@@@ Unknown protocol: "<< proto->getName() << "\n";
-        }
-
-        RuleBuilder builder(Context, System.getReferencedProtocols());
-        builder.addReferencedProtocol(proto);
-        builder.collectRulesFromReferencedProtocols();
+  assert(builder.PermanentRules.empty());
+  assert(builder.WrittenRequirements.empty());
 
-        for (const auto &rule : builder.PermanentRules)
-          System.addPermanentRule(rule.first, rule.second);
-
-        for (const auto &rule : builder.RequirementRules) {
-          auto lhs = std::get<0>(rule);
-          auto rhs = std::get<1>(rule);
-          System.addExplicitRule(lhs, rhs, /*requirementID=*/None);
-        }
-      }
-    }
-
-    auto pair = getRuleForRequirement(req.getCanonical(), /*proto=*/nullptr,
-                                      substitutions, Context);
-
-    if (Debug.contains(DebugFlags::ConditionalRequirements)) {
-      llvm::dbgs() << "@@@ Induced rule from conditional requirement: "
-                   << pair.first << " => " << pair.second << "\n";
-    }
-
-    // FIXME: Do we need a rewrite path here?
-    (void) System.addRule(pair.first, pair.second);
-  }
+  System.addRules(std::move(builder.ImportedRules),
+                  std::move(builder.PermanentRules),
+                  std::move(builder.RequirementRules));
 }

test/Generics/conditional_requirement_inference.swift

@@ -16,11 +16,21 @@ struct EquatableBox<T : Equatable> {
 // A conditional requirement with a protocol we haven't seen before.
 protocol First {}
 
-protocol Second {}
+protocol Second {
+  associatedtype X
+  associatedtype Y where X == Y
+}
 
 extension Array : First where Element : Second {}
 
+func sameType<T>(_: T.Type, _: T.Type) {}
+
 struct SillyBox<T : First> {
-  // CHECK: Generic signature: <T, U where T == Array<U>, U : Second>
-  func withArray<U>(_: U) where T == Array<U> {}
+  // Make sure we pick up the same-type requirement from 'Second' -- U.Y should
+  // minimize down to U.X.
+
+  // CHECK: Generic signature: <T, U, V where T == Array<U>, U : Second, V == U.[Second]X>
+  func withArray<U, V>(_: U) where T == Array<U>, V == U.Y {
+    sameType(U.X.self, U.Y.self)
+  }
 }