ReadonlyArray-type is not properly recognized

[Etienne-Buschong]

Describe the bug

Given a node of type ReadonlyArray<...>, the corresponding type is any.

Version: 15.1.0

To Reproduce

import { Project } from "ts-morph";

const project = new Project();
project.createSourceFile('test.ts', 'const x: ReadonlyArray<string> = [];');
const child: Node | undefined = project.getSourceFile('test.ts')?.getFirstChild();

console.log("Is array:", child?.getType().isArray()); // outputs "false"
console.log("Type text:", child?.getType().getText()); // outputs "any"
console.log("Type parameters: ", child?.getType().getTypeArguments()) // outputs "[]"

Expected behavior

The code above outputs false (for isArray()), any (for getText()) and [] (for getTypeArguments()).
The expected behaviour is that:

• isArray() outputs true. If not, how is an readonlyarray properly identified?
• getText() outputs ReadonlyArray<string>
• getTypeArguments() outputs an array of length 1

[dsherret]

Part of the reason this is occuring is because calling getFirstChild() on a source file will return its SyntaxList.

See and select Options (in top right corner) > Tree mode > getChildren():

https://ts-ast-viewer.com/#code/MYewdgzgLgBAHgLhgJQKYEMAm4A2BPAQQCcj08AeaIgSzAHMA+GAXhgG0BdAbiA

In this case, you want to get the variable declaration:

const project = new Project();
const sourceFile = project.createSourceFile('test.ts', 'const x: ReadonlyArray<string> = [];');
const varDecl = sourceFile.getVariableDeclarationOrThrow("x");

varDecl.getType().getText(); // "readonly string[]"
varDecl.getType().getTypeArguments().map(t => t.getText()); // [ "string" ]
varDecl.getType().getSymbolOrThrow().getName(); // "ReadonlyArray"

All this said, it does look like .isArray() returns false because the symbol doesn't have the name Array, but it should return it for this as well I think. Overall, it looks like the implementation of that method should be improved to be a bit more robust. I opened #1306 for that.

[Etienne-Buschong]

Regarding #1306: Would it make sense to add a distinct function isReadonlyArray() on types? Because ReadonlyArray is commonly used in many projects and it may makes sense to have a differentiation for them.