From c666e91316591d4908d4696fdf2a8d4bb16ce1a2 Mon Sep 17 00:00:00 2001
From: Matthew Preble <mpreble@indeed.com>
Date: Thu, 8 Oct 2020 17:22:57 -0500
Subject: [PATCH 1/3] fix(eslint-plugin): [no-unused-vars] fix false positives
 for duplicated names #2595

---
 .../eslint-plugin/src/rules/no-unused-vars.ts | 32 +++++++++++--------
 .../tests/rules/no-unused-vars.test.ts        | 14 ++++++++
 2 files changed, 32 insertions(+), 14 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/no-unused-vars.ts b/packages/eslint-plugin/src/rules/no-unused-vars.ts
index 7239982c9356..8753452dd097 100644
--- a/packages/eslint-plugin/src/rules/no-unused-vars.ts
+++ b/packages/eslint-plugin/src/rules/no-unused-vars.ts
@@ -1,7 +1,7 @@
 import {
-  TSESTree,
-  TSESLint,
   AST_NODE_TYPES,
+  TSESLint,
+  TSESTree,
 } from '@typescript-eslint/experimental-utils';
 import { PatternVisitor } from '@typescript-eslint/scope-manager';
 import baseRule from 'eslint/lib/rules/no-unused-vars';
@@ -327,18 +327,22 @@ export default util.createRule<Options, MessageIds>({
           break;
       }
 
-      const scope = context.getScope();
-      const { variableScope } = scope;
-      if (variableScope !== scope) {
-        for (const id of identifiers) {
-          const superVar = variableScope.set.get(id.name);
-          if (superVar) {
-            superVar.eslintUsed = true;
-          }
-        }
-      } else {
-        for (const id of identifiers) {
-          context.markVariableAsUsed(id.name);
+      let scope = context.getScope();
+      const shouldUseUpperScope = [
+        AST_NODE_TYPES.TSModuleDeclaration,
+        AST_NODE_TYPES.TSDeclareFunction,
+      ].includes(node.type);
+
+      if (scope.variableScope !== scope) {
+        scope = scope.variableScope;
+      } else if (shouldUseUpperScope && scope.upper) {
+        scope = scope.upper;
+      }
+
+      for (const id of identifiers) {
+        const superVar = scope.set.get(id.name);
+        if (superVar) {
+          superVar.eslintUsed = true;
         }
       }
     }
diff --git a/packages/eslint-plugin/tests/rules/no-unused-vars.test.ts b/packages/eslint-plugin/tests/rules/no-unused-vars.test.ts
index e22f9eb2ba7c..2a4de1d15a0d 100644
--- a/packages/eslint-plugin/tests/rules/no-unused-vars.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unused-vars.test.ts
@@ -886,6 +886,20 @@ export declare namespace Foo {
   }
 }
     `,
+    {
+      code: `
+declare namespace A {
+  export interface A {};
+}
+            `,
+      filename: 'foo.d.ts',
+    },
+    {
+      code: `
+declare function A(A: string) {}
+            `,
+      filename: 'foo.d.ts',
+    },
   ],
 
   invalid: [

From 53a2e061893e1ed4503c8e85afd311a2c95a26a8 Mon Sep 17 00:00:00 2001
From: Matthew Preble <mpreble@indeed.com>
Date: Fri, 9 Oct 2020 14:00:13 -0500
Subject: [PATCH 2/3] fix(eslint-plugin): [no-unused-vars] lint fixes

---
 .../eslint-plugin/tests/rules/no-unused-vars.test.ts     | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/packages/eslint-plugin/tests/rules/no-unused-vars.test.ts b/packages/eslint-plugin/tests/rules/no-unused-vars.test.ts
index 2a4de1d15a0d..dafb44875a20 100644
--- a/packages/eslint-plugin/tests/rules/no-unused-vars.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unused-vars.test.ts
@@ -889,15 +889,16 @@ export declare namespace Foo {
     {
       code: `
 declare namespace A {
-  export interface A {};
+  export interface A {}
 }
-            `,
+      `,
       filename: 'foo.d.ts',
     },
     {
       code: `
-declare function A(A: string) {}
-            `,
+declare function A(A: string) {
+};
+      `,
       filename: 'foo.d.ts',
     },
   ],

From eb33403c2178202f909b0c3d62db4a31d62390bd Mon Sep 17 00:00:00 2001
From: Matthew Preble <mpreble@indeed.com>
Date: Fri, 9 Oct 2020 16:03:07 -0500
Subject: [PATCH 3/3] fix(eslint-plugin): [no-unused-vars] use valid syntax in
 test case

---
 packages/eslint-plugin/tests/rules/no-unused-vars.test.ts | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/packages/eslint-plugin/tests/rules/no-unused-vars.test.ts b/packages/eslint-plugin/tests/rules/no-unused-vars.test.ts
index dafb44875a20..b3d9c92491d2 100644
--- a/packages/eslint-plugin/tests/rules/no-unused-vars.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unused-vars.test.ts
@@ -896,8 +896,7 @@ declare namespace A {
     },
     {
       code: `
-declare function A(A: string) {
-};
+declare function A(A: string): string;
       `,
       filename: 'foo.d.ts',
     },