doh

packages/svelte/src/compiler/phases/2-analyze/visitors/ClassBody.js

@@ -76,7 +76,7 @@ export function ClassBody(node, context) {
 				fields.set(key, ['prop']);
 				continue;
 			}
-			field.push('prop');
+			e.duplicate_class_field(child, key);
 		}
 
 		if (child.type === 'MethodDefinition') {
@@ -89,6 +89,9 @@ export function ClassBody(node, context) {
 					fields.set(key, [child.kind]);
 					continue;
 				}
+				if (field.includes(child.kind) || field.includes('prop')) {
+					e.duplicate_class_field(child, key);
+				}
 				if (child.kind === 'get') {
 					if (field.length === 1 && field[0] === 'set') {
 						field.push('get');