Report error only on local declaration with additional related information (#49746)

* Add test where the errors are reported in different file
Test for #49739

* Report error only on local declaration with additional related information
Fixes #49739

* Handle existing tests

tests/cases/compiler/indexSignatureInOtherFile.ts

@@ -0,0 +1,39 @@
+// @target: es2015
+// @Filename: index.ts
+class Test extends Array1 {
+  [key: symbol]: string
+}
+
+// @Filename: other.ts
+interface Array1<T> {
+  length: number;
+  [n: number]: T;
+}
+
+interface ArrayConstructor1 {
+  new(arrayLength?: number): Array1<any>;
+}
+
+declare var Array1: ArrayConstructor1;
+
+// iterable.d.ts
+interface Array1<T> {
+  [Symbol.iterator](): IterableIterator<T>;
+}
+
+// symbol.wellknown.d.ts
+interface Array1<T> {
+  /**
+   * Returns an object whose properties have the value 'true'
+   * when they will be absent when used in a 'with' statement.
+   */
+  [Symbol.unscopables](): {
+      copyWithin: boolean;
+      entries: boolean;
+      fill: boolean;
+      find: boolean;
+      findIndex: boolean;
+      keys: boolean;
+      values: boolean;
+  };
+}

tests/cases/compiler/indexSignatureInOtherFile1.ts

@@ -0,0 +1,39 @@
+// @target: es2015
+// @Filename: other.ts
+interface Array1<T> {
+  length: number;
+  [n: number]: T;
+}
+
+interface ArrayConstructor1 {
+  new(arrayLength?: number): Array1<any>;
+}
+
+declare var Array1: ArrayConstructor1;
+
+// iterable.d.ts
+interface Array1<T> {
+  [Symbol.iterator](): IterableIterator<T>;
+}
+
+// symbol.wellknown.d.ts
+interface Array1<T> {
+  /**
+   * Returns an object whose properties have the value 'true'
+   * when they will be absent when used in a 'with' statement.
+   */
+  [Symbol.unscopables](): {
+      copyWithin: boolean;
+      entries: boolean;
+      fill: boolean;
+      find: boolean;
+      findIndex: boolean;
+      keys: boolean;
+      values: boolean;
+  };
+}
+
+// @Filename: index.ts
+class Test extends Array1 {
+  [key: symbol]: string
+}