swiftlang · swift-ci · Mar 21, 2017 · Mar 21, 2017
diff --git a/include/swift/AST/DiagnosticsSema.def b/include/swift/AST/DiagnosticsSema.def
@@ -1591,11 +1591,15 @@ NOTE(superclass_redundancy_here,none,
      "superclass constraint %1 : %2 %select{written here|implied here}0",
      (bool, Type, Type))
 
-ERROR(mutiple_layout_constraints,none,
-      "multiple layout constraints cannot be used at the same time: %0 and %1",
-      (LayoutConstraint, LayoutConstraint))
+ERROR(conflicting_layout_constraints,none,
+      "%select{generic parameter |protocol |}0%1 has conflicting layout "
+      "constraints %2 and %3",
+      (unsigned, Type, LayoutConstraint, LayoutConstraint))
+WARNING(redundant_layout_constraint,none,
+        "redundant layout constraint %0 : %1", (Type, LayoutConstraint))
 NOTE(previous_layout_constraint, none,
-    "previous layout constraint declaration %0 was here", (LayoutConstraint))
+     "layout constraint constraint %1 : %2 %select{written here|implied here}0",
+     (bool, Type, LayoutConstraint))
 
 ERROR(generic_param_access,none,
       "%0 %select{must be declared %select{"

diff --git a/include/swift/AST/GenericSignatureBuilder.h b/include/swift/AST/GenericSignatureBuilder.h
@@ -128,6 +128,12 @@ class GenericSignatureBuilder {
     /// Superclass constraints written within this equivalence class.
     std::vector<ConcreteConstraint> superclassConstraints;
 
+    /// \The layout constraint for this equivalence class.
+    LayoutConstraint layout;
+
+    /// Layout constraints written within this equivalence class.
+    std::vector<Constraint<LayoutConstraint>> layoutConstraints;
+
     /// The members of the equivalence class.
     TinyPtrVector<PotentialArchetype *> members;
 
@@ -474,6 +480,11 @@ class GenericSignatureBuilder {
                             ArrayRef<GenericTypeParamType *> genericParams,
                             PotentialArchetype *pa);
 
+  /// Check layout constraints within the equivalence class of the given
+  /// potential archetype.
+  void checkLayoutConstraints(ArrayRef<GenericTypeParamType *> genericParams,
+                              PotentialArchetype *pa);
+
   /// Check same-type constraints within the equivalence class of the
   /// given potential archetype.
   void checkSameTypeConstraints(
@@ -1029,12 +1040,6 @@ class GenericSignatureBuilder::PotentialArchetype {
   mutable llvm::PointerUnion<PotentialArchetype *, EquivalenceClass *>
     representativeOrEquivClass;
 
-  /// \brief The layout constraint of this archetype, if specified.
-  LayoutConstraint Layout;
-
-  /// The source of the layout constraint requirement.
-  const RequirementSource *LayoutSource = nullptr;
-
   /// A stored nested type.
   struct StoredNestedType {
     /// The potential archetypes describing this nested type, all of which
@@ -1254,11 +1259,11 @@ class GenericSignatureBuilder::PotentialArchetype {
   }
 
   /// Retrieve the layout constraint of this archetype.
-  LayoutConstraint getLayout() const { return Layout; }
+  LayoutConstraint getLayout() const {
+    if (auto equivClass = getEquivalenceClassIfPresent())
+      return equivClass->layout;
 
-  /// Retrieve the requirement source for the layout constraint requirement.
-  const RequirementSource *getLayoutSource() const {
-    return LayoutSource;
+    return LayoutConstraint();
   }
 
   /// Retrieve the set of nested types.

diff --git a/lib/AST/GenericSignatureBuilder.cpp b/lib/AST/GenericSignatureBuilder.cpp
@@ -2069,30 +2069,19 @@ bool GenericSignatureBuilder::addConformanceRequirement(PotentialArchetype *PAT,
   return false;
 }
 
-bool GenericSignatureBuilder::addLayoutRequirement(PotentialArchetype *PAT,
-                                            LayoutConstraint Layout,
-                                            const RequirementSource *Source) {
-  // Add the requirement to the representative.
-  auto T = PAT->getRepresentative();
+bool GenericSignatureBuilder::addLayoutRequirement(
+                                             PotentialArchetype *PAT,
+                                             LayoutConstraint Layout,
+                                             const RequirementSource *Source) {
+  auto equivClass = PAT->getOrCreateEquivalenceClass();
 
-  if (T->Layout) {
-    if (T->Layout == Layout) {
-      // Update the source.
-      T->LayoutSource = Source;
-      return false;
-    }
-    // There is an existing layout constraint for this archetype.
-    Diags.diagnose(Source->getLoc(), diag::mutiple_layout_constraints,
-                   Layout, T->Layout);
-    Diags.diagnose(T->LayoutSource->getLoc(),
-                   diag::previous_layout_constraint, T->Layout);
-    T->setInvalid();
+  // Record this layout constraint.
+  equivClass->layoutConstraints.push_back({PAT, Layout, Source});
 
-    return true;
-  }
-
-  T->Layout = Layout;
-  T->LayoutSource = Source;
+  // Update the layout in the equivalence class, if we didn't have one already.
+  // FIXME: Layouts can probably be merged sensibly.
+  if (!equivClass->layout)
+    equivClass->layout = Layout;
 
   return false;
 }
@@ -3052,6 +3041,7 @@ GenericSignatureBuilder::finalize(SourceLoc loc,
     }
 
     checkConformanceConstraints(genericParams, archetype);
+    checkLayoutConstraints(genericParams, archetype);
     checkSameTypeConstraints(genericParams, archetype);
   });
 
@@ -3457,6 +3447,28 @@ void GenericSignatureBuilder::checkSuperclassConstraints(
   }
 }
 
+void GenericSignatureBuilder::checkLayoutConstraints(
+                                ArrayRef<GenericTypeParamType *> genericParams,
+                                PotentialArchetype *pa) {
+  auto equivClass = pa->getEquivalenceClassIfPresent();
+  if (!equivClass || !equivClass->layout) return;
+
+  checkConstraintList<LayoutConstraint>(
+    genericParams, equivClass->layoutConstraints,
+    [&](const Constraint<LayoutConstraint> &constraint) {
+      return constraint.value == equivClass->layout;
+    },
+    [&](LayoutConstraint layout) {
+      if (layout == equivClass->layout)
+        return ConstraintRelation::Redundant;
+
+      return ConstraintRelation::Conflicting;
+    },
+    diag::conflicting_layout_constraints,
+    diag::redundant_layout_constraint,
+    diag::previous_layout_constraint);
+}
+
 template<typename F>
 void GenericSignatureBuilder::visitPotentialArchetypes(F f) {
   // Stack containing all of the potential archetypes to visit.
@@ -3748,16 +3760,24 @@ void GenericSignatureBuilder::enumerateRequirements(llvm::function_ref<
     if (archetype != archetype->getArchetypeAnchor(*this))
       continue;
 
+    auto equivClass = rep->getEquivalenceClassIfPresent();
+
     // If we have a layout constraint, produce a layout requirement.
-    if (LayoutConstraint Layout = archetype->getLayout()) {
-      f(RequirementKind::Layout, archetype, Layout,
-        archetype->getLayoutSource());
+    if (equivClass && equivClass->layout) {
+      // Find the best source among the constraints that describe the layout
+      // of this type.
+      auto bestSource = equivClass->layoutConstraints.front().source;
+      for (const auto &constraint : equivClass->layoutConstraints) {
+        if (constraint.source->compare(bestSource) < 0)
+          bestSource = constraint.source;
+      }
+
+      f(RequirementKind::Layout, archetype, equivClass->layout, bestSource);
     }
 
     // Enumerate conformance requirements.
     SmallVector<ProtocolDecl *, 4> protocols;
     DenseMap<ProtocolDecl *, const RequirementSource *> protocolSources;
-    auto equivClass = rep->getEquivalenceClassIfPresent();
     if (equivClass) {
       for (const auto &conforms : equivClass->conformsTo) {
         protocols.push_back(conforms.first);

diff --git a/test/attr/attr_specialize.swift b/test/attr/attr_specialize.swift
@@ -157,7 +157,11 @@ public func anotherFuncWithTwoGenericParameters<X: P, Y>(x: X, y: Y) {
 func funcWithForbiddenSpecializeRequirement<T>(_ t: T) {
 }
 
-@_specialize(where T: _Trivial(32), T: _Trivial(64), T: _Trivial, T: _RefCountedObject) // expected-error{{multiple layout constraints cannot be used at the same time: '_Trivial(64)' and '_Trivial(32)'}} expected-note{{previous layout constraint declaration '_Trivial(32)' was here}} expected-error{{multiple layout constraints cannot be used at the same time: '_Trivial' and '_Trivial(32)'}} expected-note{{previous layout constraint declaration '_Trivial(32)' was here}} expected-error{{multiple layout constraints cannot be used at the same time: '_RefCountedObject' and '_Trivial(32)'}} expected-note{{previous layout constraint declaration '_Trivial(32)' was here}}
+@_specialize(where T: _Trivial(32), T: _Trivial(64), T: _Trivial, T: _RefCountedObject)
+// expected-error@-1{{generic parameter 'T' has conflicting layout constraints '_Trivial(64)' and '_Trivial(32)'}}
+// expected-error@-2{{generic parameter 'T' has conflicting layout constraints '_RefCountedObject' and '_Trivial(32)'}}
+// expected-error@-3{{generic parameter 'T' has conflicting layout constraints '_Trivial' and '_Trivial(32)'}}
+// expected-note@-4 3{{layout constraint constraint 'T' : '_Trivial(32)' written here}}
 @_specialize(where Array<T> == Int) // expected-error{{Only requirements on generic parameters are supported by '_specialize' attribute}}
 // expected-error@-1{{generic signature requires types 'Array<T>' and 'Int' to be the same}}
 @_specialize(where T.Element == Int) // expected-error{{Only requirements on generic parameters are supported by '_specialize' attribute}}