Diagnose @objc(selector) access note conflicts

Author: beccadax

include/swift/AST/DiagnosticsSema.def

@@ -5670,6 +5670,10 @@ WARNING(attr_objc_name_changed_by_access_note, none,
 WARNING(fixit_attr_objc_name_changed_by_access_note, none,
         "change '@objc' name in source code explicitly to silence this warning",
         ())
+WARNING(attr_objc_name_conflicts_with_access_note, none,
+        "access note for %0 changes the '@objc' name of this %1 to %2, but "
+        "source code specifies %3; the access note will be ignored",
+        (StringRef, DescriptiveDeclKind, ObjCSelector, ObjCSelector))
 
 #define UNDEFINE_DIAGNOSTIC_MACROS
 #include "DefineDiagnosticMacros.h"

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -1534,9 +1534,10 @@ static void applyAccessNote(ValueDecl *VD, const AccessNote &note,
         note.fixItInsertAfter(attr->getLocation(), newNameString);
     }
     else if (attr->getName() != *note.ObjCName) {
-      // TODO: diagnose conflict between explicit name in code and explicit
-      // name in access note
-      llvm::report_fatal_error("conflict between name in code and name in access note");
+      diagnoseForAccessNote(attr, VD,
+                            diag::attr_objc_name_conflicts_with_access_note,
+                            notes.reason, VD->getDescriptiveKind(),
+                            *note.ObjCName, *attr->getName());
     }
   }
 }

test/SILGen/Inputs/objc_access_notes.accessnotes

@@ -53,3 +53,4 @@ Notes:
   ObjC: true
 - Name: 'Wotsit.plain()'
   ObjC: true
+  ObjCName: 'fancy'

test/SILGen/objc_access_notes.swift

@@ -456,9 +456,9 @@ class Wotsit<T> : Gizmo {
   // CHECK-NEXT: destroy_value [[SELF_COPY]] : $Wotsit<T>
   // CHECK-NEXT: return [[RESULT]] : $()
   // CHECK-NEXT: }
+  @objc(plain)
   func plain() { }
-  // expected-warning@-1 {{access note for fancy test suite adds attribute 'objc' to this instance method}}
-  // expected-note@-2 {{add attribute explicitly to silence this warning}} {{3-3=@objc }}
+  // expected-warning@-2 {{access note for fancy test suite changes the '@objc' name of this instance method to 'fancy', but source code specifies 'plain'; the access note will be ignored}}
 
   func generic<U>(_ x: U) {}