GSB: Diagnose redundant layout requirements using the redundant requirement graph

Author: slavapestov

include/swift/AST/DiagnosticsSema.def

@@ -2425,15 +2425,17 @@ NOTE(superclass_redundancy_here,none,
      (unsigned, Type, Type))
 
 ERROR(conflicting_layout_constraints,none,
-      "%select{generic parameter |protocol |}0%1 has conflicting "
-      "constraints %2 and %3",
-      (unsigned, Type, LayoutConstraint, LayoutConstraint))
+      "type %0 has conflicting constraints %1 and %2",
+      (Type, LayoutConstraint, LayoutConstraint))
+NOTE(conflicting_layout_constraint, none,
+     "constraint conflicts with %0 : %1",
+     (Type, LayoutConstraint))
 WARNING(redundant_layout_constraint,none,
-        "redundant constraint %0 : %1", (Type, LayoutConstraint))
+        "redundant constraint %0 : %1",
+        (Type, LayoutConstraint))
 NOTE(previous_layout_constraint, none,
-     "constraint %1 : %2 %select{written here|implied here|"
-     "inferred from type here}0",
-     (unsigned, Type, LayoutConstraint))
+     "constraint %0 : %1 implied here",
+     (Type, LayoutConstraint))
 
 WARNING(redundant_same_type_constraint,none,
         "redundant same-type constraint %0 == %1", (Type, Type))

lib/AST/GenericSignatureBuilder.cpp

@@ -7113,8 +7113,45 @@ void GenericSignatureBuilder::diagnoseRedundantRequirements() const {
       break;
     }
 
+    case RequirementKind::Layout: {
+      auto layout = req.getRHS().get<LayoutConstraint>();
+
+      auto conflict = Impl->ConflictingRequirements.find(req);
+      if (conflict != Impl->ConflictingRequirements.end()) {
+        Impl->HadAnyError = true;
+
+        auto otherLayout = conflict->second.get<LayoutConstraint>();
+        Context.Diags.diagnose(loc, diag::conflicting_layout_constraints,
+                               subjectType, layout, otherLayout);
+
+        for (auto otherReq : found->second) {
+          auto *otherSource = otherReq.getSource();
+          auto otherLoc = otherSource->getLoc();
+          if (otherLoc.isInvalid())
+            continue;
+
+          Context.Diags.diagnose(otherLoc, diag::conflicting_layout_constraint,
+                                 subjectType, otherLayout);
+        }
+      } else {
+        Context.Diags.diagnose(loc, diag::redundant_layout_constraint,
+                               subjectType, layout);
+
+        for (auto otherReq : found->second) {
+          auto *otherSource = otherReq.getSource();
+          auto otherLoc = otherSource->getLoc();
+          if (otherLoc.isInvalid())
+            continue;
+
+          Context.Diags.diagnose(otherLoc, diag::previous_layout_constraint,
+                                 subjectType, layout);
+        }
+      }
+
+      break;
+    }
+
     case RequirementKind::Superclass:
-    case RequirementKind::Layout:
     case RequirementKind::SameType:
       // TODO
       break;
@@ -8023,24 +8060,7 @@ void GenericSignatureBuilder::checkLayoutConstraints(
                               EquivalenceClass *equivClass) {
   if (!equivClass->layout) return;
 
-  checkConstraintList<LayoutConstraint>(
-    genericParams, equivClass->layoutConstraints, RequirementKind::Layout,
-    [&](const Constraint<LayoutConstraint> &constraint) {
-      return constraint.value == equivClass->layout;
-    },
-    [&](const Constraint<LayoutConstraint> &constraint) {
-      auto layout = constraint.value;
-
-      // If the layout constraints are mergable, i.e. compatible,
-      // it is a redundancy.
-      if (layout.merge(equivClass->layout)->isKnownLayout())
-        return ConstraintRelation::Redundant;
-
-      return ConstraintRelation::Conflicting;
-    },
-    diag::conflicting_layout_constraints,
-    diag::redundant_layout_constraint,
-    diag::previous_layout_constraint);
+  removeSelfDerived(*this, equivClass->layoutConstraints, /*proto=*/nullptr);
 }
 
 bool GenericSignatureBuilder::isRedundantExplicitRequirement(

test/Compatibility/anyobject_class.swift

@@ -3,4 +3,4 @@
 
 protocol P : class, AnyObject { } // expected-warning{{redundant inheritance from 'AnyObject' and Swift 3 'class' keyword}}{{14-21=}}
 // expected-warning@-1{{redundant constraint 'Self' : 'AnyObject'}}
-// expected-note@-2{{constraint 'Self' : 'AnyObject' written here}}
+// expected-note@-2{{constraint 'Self' : 'AnyObject' implied here}}

test/attr/attr_specialize.swift

@@ -171,16 +171,17 @@ func funcWithForbiddenSpecializeRequirement<T>(_ t: T) {
 }
 
 @_specialize(where T: _Trivial(32), T: _Trivial(64), T: _Trivial, T: _RefCountedObject)
-// expected-error@-1{{generic parameter 'T' has conflicting constraints '_Trivial(64)' and '_Trivial(32)'}}
-// expected-error@-2{{generic parameter 'T' has conflicting constraints '_RefCountedObject' and '_Trivial(32)'}}
+// expected-error@-1{{type 'T' has conflicting constraints '_Trivial(64)' and '_Trivial(32)'}}
+// expected-error@-2{{type 'T' has conflicting constraints '_RefCountedObject' and '_Trivial(32)'}}
 // expected-warning@-3{{redundant constraint 'T' : '_Trivial'}}
-// expected-note@-4 3{{constraint 'T' : '_Trivial(32)' written here}}
+// expected-note@-4 {{constraint 'T' : '_Trivial' implied here}}
+// expected-note@-5 2{{constraint conflicts with 'T' : '_Trivial(32)'}}
 @_specialize(where T: _Trivial, T: _Trivial(64))
 // expected-warning@-1{{redundant constraint 'T' : '_Trivial'}}
-// expected-note@-2 1{{constraint 'T' : '_Trivial(64)' written here}}
+// expected-note@-2 1{{constraint 'T' : '_Trivial' implied here}}
 @_specialize(where T: _RefCountedObject, T: _NativeRefCountedObject)
 // expected-warning@-1{{redundant constraint 'T' : '_RefCountedObject'}}
-// expected-note@-2 1{{constraint 'T' : '_NativeRefCountedObject' written here}}
+// expected-note@-2 1{{constraint 'T' : '_RefCountedObject' implied here}}
 @_specialize(where Array<T> == Int) // expected-error{{generic signature requires types 'Array<T>' and 'Int' to be the same}}
 // expected-error@-1 {{too few generic parameters are specified in '_specialize' attribute (got 0, but expected 1)}}
 // expected-note@-2 {{missing constraint for 'T' in '_specialize' attribute}}
@@ -193,14 +194,15 @@ public protocol Proto: class {
 }
 
 @_specialize(where T: _RefCountedObject)
-// expected-error@-1 {{too few generic parameters are specified in '_specialize' attribute (got 0, but expected 1)}}
-// expected-note@-2 {{missing constraint for 'T' in '_specialize' attribute}}
+// expected-warning@-1 {{redundant constraint 'T' : '_RefCountedObject'}}
+// expected-error@-2 {{too few generic parameters are specified in '_specialize' attribute (got 0, but expected 1)}}
+// expected-note@-3 {{missing constraint for 'T' in '_specialize' attribute}}
 @_specialize(where T: _Trivial)
-// expected-error@-1{{generic parameter 'T' has conflicting constraints '_Trivial' and '_NativeClass'}}
+// expected-error@-1{{type 'T' has conflicting constraints '_Trivial' and '_NativeClass'}}
 // expected-error@-2 {{too few generic parameters are specified in '_specialize' attribute (got 0, but expected 1)}}
 // expected-note@-3 {{missing constraint for 'T' in '_specialize' attribute}}
 @_specialize(where T: _Trivial(64))
-// expected-error@-1{{generic parameter 'T' has conflicting constraints '_Trivial(64)' and '_NativeClass'}}
+// expected-error@-1{{type 'T' has conflicting constraints '_Trivial(64)' and '_NativeClass'}}
 // expected-error@-2 {{too few generic parameters are specified in '_specialize' attribute (got 0, but expected 1)}}
 // expected-note@-3 {{missing constraint for 'T' in '_specialize' attribute}}
 public func funcWithABaseClassRequirement<T>(t: T) -> Int where T: C1 {

test/decl/ext/extensions.swift

@@ -259,7 +259,7 @@ class JustAClass2: ImposeClassReq1 {
   var someProperty = 0
 }
 
-extension ImposeClassReq1 where Self: AnyObject {
+extension ImposeClassReq1 where Self: AnyObject { // expected-warning {{redundant constraint 'Self' : 'AnyObject'}}
   var wrappingProperty1: Int {
     get { return someProperty }
     set { someProperty = newValue }