fix(eslint-plugin): [unified-signatures] type comparison and exported nodes

packages/eslint-plugin/src/rules/unified-signatures.ts

@@ -35,6 +35,9 @@ type ScopeNode =
   | TSESTree.TSTypeLiteral;
 
 type OverloadNode = MethodDefinition | SignatureDefinition;
+type ContainingNode =
+  | TSESTree.ExportNamedDeclaration
+  | TSESTree.ExportDefaultDeclaration;
 
 type SignatureDefinition =
   | TSESTree.FunctionExpression
@@ -495,9 +498,17 @@ export default util.createRule({
       currentScope = scopes.pop()!;
     }
 
-    function addOverload(signature: OverloadNode, key?: string): void {
+    function addOverload(
+      signature: OverloadNode,
+      key?: string,
+      containingNode?: ContainingNode,
+    ): void {
       key = key || getOverloadKey(signature);
-      if (currentScope && signature.parent === currentScope.parent && key) {
+      if (
+        currentScope &&
+        (containingNode || signature).parent === currentScope.parent &&
+        key
+      ) {
         const overloads = currentScope.overloads.get(key);
         if (overloads !== undefined) {
           overloads.push(signature);
@@ -521,11 +532,10 @@ export default util.createRule({
         createScope(node.body, node.typeParameters);
       },
       TSTypeLiteral: createScope,
+
       // collect overloads
       TSDeclareFunction(node): void {
-        if (node.id && !node.body) {
-          addOverload(node, node.id.name);
-        }
+        addOverload(node, node.id!.name, getExportingNode(node));
       },
       TSCallSignatureDeclaration: addOverload,
       TSConstructSignatureDeclaration: addOverload,
@@ -540,6 +550,7 @@ export default util.createRule({
           addOverload(node);
         }
       },
+
       // validate scopes
       'Program:exit': checkScope,
       'TSModuleBlock:exit': checkScope,
@@ -550,6 +561,14 @@ export default util.createRule({
   },
 });
 
+function getExportingNode(node: TSESTree.TSDeclareFunction) {
+  return node.parent &&
+    (node.parent.type === AST_NODE_TYPES.ExportNamedDeclaration ||
+      node.parent.type === AST_NODE_TYPES.ExportDefaultDeclaration)
+    ? node.parent
+    : undefined;
+}
+
 function getOverloadKey(node: OverloadNode): string | undefined {
   const info = getOverloadInfo(node);
 

packages/eslint-plugin/tests/rules/unified-signatures.test.ts

@@ -591,5 +591,39 @@ class Foo {
         },
       ],
     },
+    {
+      code: `
+export function foo(line: number): number;
+export function foo(line: number, character?: number): number;
+`,
+      errors: [
+        {
+          messageId: 'omittingSingleParameter',
+          data: {
+            failureStringStart:
+              'These overloads can be combined into one signature',
+          },
+          line: 3,
+          column: 35,
+        },
+      ],
+    },
+    {
+      code: `
+declare function foo(line: number): number;
+export function foo(line: number, character?: number): number;
+`,
+      errors: [
+        {
+          messageId: 'omittingSingleParameter',
+          data: {
+            failureStringStart:
+              'These overloads can be combined into one signature',
+          },
+          line: 3,
+          column: 35,
+        },
+      ],
+    },
   ],
 });