fix: handle undefined typeParameters (#1495)

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## PR Checklist

- [x] Addresses an existing open issue: fixes #1427 
- [x] That issue was marked as [`status: accepting
prs`](https://github.com/JoshuaKGoldberg/TypeStat/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/JoshuaKGoldberg/TypeStat/blob/main/.github/CONTRIBUTING.md)
were taken 🐙

## Overview

<!-- Description of what is changed and how the code change does that.
-->

`templatedDeclaration.typeParameters` was undefined in some situations,
which threw an error. Added new regression test category as this is not
really test about how the fixes work otherwise. Probably the test case
could be simplified, but I'm going with mindset that fixed bug is better
than none.

---------

Co-authored-by: rubiesonthesky <rubiesonthesky>
Co-authored-by: Josh Goldberg ✨ <[email protected]>

src/mutators/builtIn/fixIncompleteTypes/fixIncompleteInterfaceOrTypeLiteralGenerics/collectGenericNodeReferences.ts

@@ -4,8 +4,8 @@ import { FileMutationsRequest } from "../../../../shared/fileMutator.js";
 import {
 	getIdentifyingTypeLiteralParent,
 	isNodeWithDefinedTypeArguments,
-	isNodeWithDefinedTypeParameters,
 	isNodeWithIdentifierName,
+	isNodeWithTypeParameters,
 } from "../../../../shared/nodeTypes.js";
 import { isTypeArgumentsType } from "../../../../shared/typeNodes.js";
 import { getTypeAtLocationIfNotError } from "../../../../shared/types.js";
@@ -84,8 +84,9 @@ export const expandReferencesForGenericTypes = (
 		const templatedDeclaration = templatedDeclarationSymbol.valueDeclaration;
 		if (
 			templatedDeclaration === undefined ||
-			!isNodeWithDefinedTypeParameters(templatedDeclaration) ||
-			templatedParentInstantiation.typeArguments === undefined
+			!isNodeWithTypeParameters(templatedDeclaration) ||
+			templatedParentInstantiation.typeArguments === undefined ||
+			templatedDeclaration.typeParameters === undefined
 		) {
 			continue;
 		}

src/shared/nodeTypes.ts

@@ -64,8 +64,8 @@ export type NodeWithDefinedTypeArguments = ts.Node & {
 
 // TODO: make this a more specific type
 // Will have to deal with instantiations (new Container<T>() { ... }) and declarations (class Container<T>() { ... }))
-export type NodeWithDefinedTypeParameters = ts.Node & {
-	typeParameters: ts.NodeArray<ts.TypeNode>;
+export type NodeWithTypeParameters = ts.Node & {
+	typeParameters: ts.NodeArray<ts.TypeNode> | undefined;
 };
 
 export const isNodeWithType = (
@@ -84,9 +84,9 @@ export const isNodeWithDefinedTypeArguments = (
 	return "typeArguments" in node;
 };
 
-export const isNodeWithDefinedTypeParameters = (
+export const isNodeWithTypeParameters = (
 	node: ts.Node,
-): node is NodeWithDefinedTypeParameters => {
+): node is NodeWithTypeParameters => {
 	return "typeParameters" in node;
 };
 

test/cases/fixes/incompleteTypes/nonGenericInterfaceAsTypeArgument/expected.ts

@@ -0,0 +1,7 @@
+(function () {
+	interface Shape {
+		value?: unknown;
+	}
+
+	[].reduce<Shape>(() => ({}), {});
+})();

test/cases/fixes/incompleteTypes/nonGenericInterfaceAsTypeArgument/original.ts

@@ -0,0 +1,7 @@
+(function () {
+	interface Shape {
+		value?: unknown;
+	}
+
+	[].reduce<Shape>(() => ({}), {});
+})();

test/cases/fixes/incompleteTypes/nonGenericInterfaceAsTypeArgument/tsconfig.json

@@ -0,0 +1,3 @@
+{
+	"files": ["actual.ts"]
+}

test/cases/fixes/incompleteTypes/nonGenericInterfaceAsTypeArgument/typestat.json

@@ -0,0 +1,5 @@
+{
+	"fixes": {
+		"incompleteTypes": true
+	}
+}