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fix(eslint-plugin): [no-use-before-define] correctly handle typeof type references #2623

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merged 3 commits into from Oct 11, 2020
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fix(eslint-plugin): [no-use-before-define] correctly handle typeof type references #2623

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88c43f5
fix(eslint-plugin): Added typeof keyword check
Drakota Oct 2, 2020
7ac122a
fix(eslint-plugin): checking for typeQuery on any depth
Drakota Oct 4, 2020
2650582
fix(eslint-plugin): constraining referenceContainsTypeQuery
Drakota Oct 10, 2020
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12 changes: 11 additions & 1 deletion packages/eslint-plugin/src/rules/no-use-before-define.ts
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Expand Up @@ -92,6 +92,16 @@ function isOuterVariable(
);
}

/**
* Checks whether or not a given reference is a type reference.
*/
function isTypeReference(reference: TSESLint.Scope.Reference): boolean {
return (
reference.isTypeReference ||
reference.identifier.parent?.parent?.type === AST_NODE_TYPES.TSTypeQuery
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almost! but this will only match one case.

We need to match all of these cases, and more:

  • typeof a
  • typeof a.b
  • typeof a.b.c

Instead an easier way to do this would be with a loop.
Based on the defined types for TSTypeQuery, we know that the exprName will either be an Identifier or a TSQualifiedName.

typescript-eslint/packages/types/src/ts-estree.ts

Lines 1669 to 1672 in d7dc108

export interface TSTypeQuery extends BaseNode {
type: AST_NODE_TYPES.TSTypeQuery;
exprName: EntityName;
}

Based on the defined types for TSQualifiedName, we know the left will always be an Identifier or a TSQualifiedName.

typescript-eslint/packages/types/src/ts-estree.ts

Lines 1572 to 1576 in d7dc108

export interface TSQualifiedName extends BaseNode {
type: AST_NODE_TYPES.TSQualifiedName;
left: EntityName;
right: Identifier;
}

This means we can simply loop and look at the parents
The reason I gave you the above is it'll help you constrain the loop so it won't iterate forever

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Fixed!

);
}

/**
* Checks whether or not a given location is inside of the range of a given node.
*/
Expand Down Expand Up @@ -219,7 +229,7 @@ export default util.createRule<Options, MessageIds>({
variable: TSESLint.Scope.Variable,
reference: TSESLint.Scope.Reference,
): boolean {
if (reference.isTypeReference && options.ignoreTypeReferences) {
if (isTypeReference(reference) && options.ignoreTypeReferences) {
return false;
}
if (isFunction(variable)) {
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22 changes: 22 additions & 0 deletions packages/eslint-plugin/tests/rules/no-use-before-define.test.ts
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Expand Up @@ -219,7 +219,29 @@ type Foo = string | number;
`,
options: [{ typedefs: false }],
},
// https://github.com/typescript-eslint/typescript-eslint/issues/2572
{
code: `
interface Bar {
type: typeof Foo.FOO;
}

class Foo {
public static readonly FOO = '';
}
`,
options: [{ ignoreTypeReferences: true }],
},
{
code: `
const foo = 2;

interface Bar {
type: typeof foo;
}
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`,
options: [{ ignoreTypeReferences: true }],
},
// https://github.com/bradzacher/eslint-plugin-typescript/issues/141
{
code: `
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