[Sema] Emit a duplicate inheritance error for duplicate 'Any' conformances

Previously, for the following:

    struct S : Any, Any {}

we would just emit two warnings. But in the interest of consistency, this commit changes the behaviour such that we instead emit a warning and an error for the duplicate conformance.

Author: hamishknight

lib/Sema/TypeCheckDecl.cpp

@@ -409,25 +409,6 @@ void TypeChecker::checkInheritanceClause(Decl *decl,
     auto isConstraint =
         isa<AbstractTypeParamDecl>(decl) || isa<ProtocolDecl>(decl);
 
-    // Check for a stated conformance to Any, which is redundant.
-    // Ignore cases of ': Any' *constraints* that are parsed as inheritance
-    // clauses, such as with protocol and placeholder decls e.g <T : Any>, as
-    // these are handled by the generic signature builder along with redundant
-    // constraints that appear in 'where' clauses.
-    if (inheritedCanTy == Context.TheAnyType) {
-      if (!isConstraint) {
-        auto diagLoc = inherited.getSourceRange().Start;
-        auto diag = diagnose(diagLoc, diag::redundant_conformance_warning,
-                             declInterfaceTy, inheritedTy);
-        diag.highlight(inherited.getSourceRange());
-        tryAddRemovalFixIt(diag, i);
-        diag.flush();
-
-        diagnose(diagLoc, diag::all_types_implicitly_conform_to, inheritedTy);
-      }
-      continue;
-    }
-
     // Check whether we inherited from the same type twice.
     auto knownType = inheritedTypes.find(inheritedCanTy);
     if (knownType != inheritedTypes.end()) {
@@ -458,6 +439,25 @@ void TypeChecker::checkInheritanceClause(Decl *decl,
     }
     inheritedTypes[inheritedCanTy] = { i, inherited.getSourceRange() };
 
+    // Check for a stated conformance to Any, which is redundant.
+    // Ignore cases of ': Any' *constraints* that are parsed as inheritance
+    // clauses, such as with protocol and placeholder decls e.g <T : Any>, as
+    // these are handled by the generic signature builder along with redundant
+    // constraints that appear in 'where' clauses.
+    if (inheritedCanTy == Context.TheAnyType) {
+      if (!isConstraint) {
+        auto diagLoc = inherited.getSourceRange().Start;
+        auto diag = diagnose(diagLoc, diag::redundant_conformance_warning,
+                             declInterfaceTy, inheritedTy);
+        diag.highlight(inherited.getSourceRange());
+        tryAddRemovalFixIt(diag, i);
+        diag.flush();
+
+        diagnose(diagLoc, diag::all_types_implicitly_conform_to, inheritedTy);
+      }
+      continue;
+    }
+
     if (inheritedTy->isExistentialType()) {
       auto layout = inheritedTy->getExistentialLayout();
 

test/FixCode/fixits-redundant-any.swift.result

@@ -43,12 +43,12 @@ class C7 : Any, AnyObject {}
 // FIX-ME: Implement redundant Any fix-its for requirements parsed as inheritance clauses.
 struct S12<T : Any> {}
 protocol P2 : Any {}
-protocol P3 : Any, Any {}
+protocol P3 : Any {}
 protocol P4 : class, Any, AnyObject {} // Parse will re-arrange 'class' to be first.
 protocol P5 : Any, AnyObject {}
 protocol P6 : AnyObject, Any {}
 
 protocol P7 {
   associatedtype X1 : Any
-  associatedtype X2 : Any, Any
+  associatedtype X2 : Any
 }

test/Generics/redundant_constraints.swift

@@ -75,7 +75,7 @@ protocol P4 {
   // expected-warning@-11 {{redundant conformance constraint 'Self.X3': 'Any'}} {{37-47=}}
   // expected-note@-12 {{all types implicitly conform to 'Any'}}
 
-  associatedtype X1 : Any, Any
+  associatedtype X1 : Any, Any // expected-error {{duplicate inheritance from 'Any'}} {{26-31=}}
   associatedtype X2 where X2 : Any, X2 : Any
   associatedtype X3 where X3 : Any, X3 : Any, X3 : P1
 }
@@ -91,6 +91,7 @@ protocol P7 : Any, Any {}
 // expected-note@-2 {{all types implicitly conform to 'Any'}}
 // expected-warning@-3 {{redundant conformance constraint 'Self': 'Any'}}
 // expected-note@-4 {{all types implicitly conform to 'Any'}}
+// expected-error@-5 {{duplicate inheritance from 'Any'}} {{18-23=}}
 
 func f1<T : Any>(_ x: T) {} // expected-warning {{redundant conformance constraint 'T': 'Any'}}
 // expected-note@-1 {{all types implicitly conform to 'Any'}}

test/decl/protocol/protocols.swift

@@ -110,8 +110,7 @@ class X11 : AnyAnyAlias {} // expected-warning {{redundant conformance of 'X11'
 struct X12 : Any, Any {}
 // expected-warning@-1 {{redundant conformance of 'X12' to 'Any'}} {{14-19=}}
 // expected-note@-2 {{all types implicitly conform to 'Any'}}
-// expected-warning@-3 {{redundant conformance of 'X12' to 'Any'}} // FIX-ME(SR-8102): Add expected fix-it {{17-22=}}
-// expected-note@-4 {{all types implicitly conform to 'Any'}}
+// expected-error@-3 {{duplicate inheritance from 'Any'}} // FIX-ME(SR-8102): Add expected fix-it {{17-22=}}
 
 // Explicit conformance checks (unsuccessful)