declarations of abstract methods must be consecutive

src/compiler/checker.ts

@@ -9191,9 +9191,6 @@ namespace ts {
                     return;
                 }
 
-                // Abstract methods can't have an implementation -- in particular, they don't need one.
-                if (node.flags & NodeFlags.Abstract) { return; }
-
                 let seen = false;
                 let subsequentNode = forEachChild(node.parent, c => {
                     if (seen) {
@@ -9226,7 +9223,13 @@ namespace ts {
                     error(errorNode, Diagnostics.Constructor_implementation_is_missing);
                 }
                 else {
-                    error(errorNode, Diagnostics.Function_implementation_is_missing_or_not_immediately_following_the_declaration);
+                    // Report different errors regarding non-consecutive blocks of declarations depending on whether
+                    // the node in question is abstract.
+                    if (node.flags & NodeFlags.Abstract) {
+                        error(errorNode, Diagnostics.All_declarations_of_an_abstract_member_function_must_be_consecutive);
+                    } else {
+                        error(errorNode, Diagnostics.Function_implementation_is_missing_or_not_immediately_following_the_declaration);
+                    }
                 }
             }
 
@@ -9303,7 +9306,8 @@ namespace ts {
                 });
             }
 
-            if (!isExportSymbolInsideModule && lastSeenNonAmbientDeclaration && !lastSeenNonAmbientDeclaration.body) {
+            // Abstract methods can't have an implementation -- in particular, they don't need one.
+            if (!isExportSymbolInsideModule && lastSeenNonAmbientDeclaration && !lastSeenNonAmbientDeclaration.body && !(lastSeenNonAmbientDeclaration.flags & NodeFlags.Abstract) ) {
                 reportImplementationExpectedError(lastSeenNonAmbientDeclaration);
             }
 

src/compiler/diagnosticInformationMap.generated.ts

@@ -398,6 +398,7 @@ namespace ts {
         Abstract_member_function_0_on_type_1_cannot_be_called_via_super_expression: { code: 2513, category: DiagnosticCategory.Error, key: "Abstract member function '{0}' on type '{1}' cannot be called via super expression." },
         Classes_containing_abstract_functions_must_be_marked_abstract: { code: 2514, category: DiagnosticCategory.Error, key: "Classes containing abstract functions must be marked abstract." },
         Non_abstract_class_0_does_not_implement_inherited_abstract_member_1_2: { code: 2515, category: DiagnosticCategory.Error, key: "Non-abstract class '{0}' does not implement inherited abstract member '{1}.{2}'." },
+        All_declarations_of_an_abstract_member_function_must_be_consecutive: { code: 2516, category: DiagnosticCategory.Error, key: "All declarations of an abstract member function must be consecutive." },
         Import_declaration_0_is_using_private_name_1: { code: 4000, category: DiagnosticCategory.Error, key: "Import declaration '{0}' is using private name '{1}'." },
         Type_parameter_0_of_exported_class_has_or_is_using_private_name_1: { code: 4002, category: DiagnosticCategory.Error, key: "Type parameter '{0}' of exported class has or is using private name '{1}'." },
         Type_parameter_0_of_exported_interface_has_or_is_using_private_name_1: { code: 4004, category: DiagnosticCategory.Error, key: "Type parameter '{0}' of exported interface has or is using private name '{1}'." },

src/compiler/diagnosticMessages.json

@@ -1579,6 +1579,10 @@
         "category": "Error",
         "code": 2515
     },
+    "All declarations of an abstract member function must be consecutive.": {
+        "category": "Error",
+        "code": 2516
+    },
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
         "code": 4000