refactor diagnostics

Author: collin5

src/compiler/checker.ts

@@ -6288,9 +6288,9 @@ namespace ts {
                         // If we have an existing early-bound member, combine its declarations so that we can
                         // report an error at each declaration.
                         const declarations = earlySymbol ? concatenate(earlySymbol.declarations, lateSymbol.declarations) : lateSymbol.declarations;
-                        const name = (<LiteralType>type).value || declarationNameToString(decl.name)
-                        forEach(declarations, declaration => error(getNameOfDeclaration(declaration) || declaration, Diagnostics.Duplicate_declaration_0, name));
-                        error(decl.name || decl, Diagnostics.Duplicate_declaration_0, name);
+                        const name = (<LiteralType>type).value || declarationNameToString(decl.name);
+                        forEach(declarations, declaration => error(getNameOfDeclaration(declaration) || declaration, Diagnostics.Duplicate_property_0, name));
+                        error(decl.name || decl, Diagnostics.Duplicate_property_0, name);
                         lateSymbol = createSymbol(SymbolFlags.None, memberName, CheckFlags.Late);
                     }
                     lateSymbol.nameType = type;

src/compiler/diagnosticMessages.json

@@ -2425,7 +2425,7 @@
         "category": "Error",
         "code": 2717
     },
-    "Duplicate declaration '{0}'.": {
+    "Duplicate property '{0}'.": {
         "category": "Error",
         "code": 2718
     },