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chore: check variable declaration syntax error against tsNode #11778

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chore: check variable declaration syntax error against tsNode #11778

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0603fcb
chore: check `VariableDeclaration` syntax error against tsNode
fisker Nov 23, 2025
ad1341f
Rename `hasExclamationToken`
fisker Nov 23, 2025
50bd39f
Fix `VariableDeclarationList`
fisker Nov 23, 2025
fe1572f
Prepare for VariableStatement
fisker Nov 23, 2025
04fe79a
Fix `VariableStatement`
fisker Nov 23, 2025
0cf79f9
Linting
fisker Nov 26, 2025
ee14ac5
Merge branch 'main' into variable-declare-check
fisker Dec 1, 2025
b98e549
Fix bad merge
fisker Dec 1, 2025
564f521
Reduce diff
fisker Dec 1, 2025
0f67400
Revert
fisker Dec 1, 2025
f28b14a
Another
fisker Dec 1, 2025
a7fdcfc
Merge branch 'main' into variable-declare-check
fisker Dec 1, 2025
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177 changes: 97 additions & 80 deletions packages/typescript-estree/src/convert.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -974,9 +974,9 @@ export class Converter {
}

case SyntaxKind.VariableDeclaration: {
const definite = !!node.exclamationToken;
const hasExclamationToken = !!node.exclamationToken;

if (definite) {
if (hasExclamationToken) {
if (node.initializer) {
this.#throwError(
node,
Expand All @@ -990,6 +990,90 @@ export class Converter {
}
}

if (node.parent.kind === SyntaxKind.VariableDeclarationList) {
const variableDeclarationList = node.parent;
const kind = getDeclarationKind(variableDeclarationList);

if (
(variableDeclarationList.parent.kind ===
SyntaxKind.ForInStatement ||
variableDeclarationList.parent.kind ===
SyntaxKind.ForStatement) &&
(kind === 'using' || kind === 'await using')
) {
if (!node.initializer) {
this.#throwError(
node,
`'${kind}' declarations may not be initialized in for statement.`,
);
}

if (node.name.kind !== SyntaxKind.Identifier) {
this.#throwError(
node.name,
`'${kind}' declarations may not have binding patterns.`,
);
}
}

if (
variableDeclarationList.parent.kind === SyntaxKind.VariableStatement
) {
const variableStatement = variableDeclarationList.parent;

if (kind === 'using' || kind === 'await using') {
if (!node.initializer) {
this.#throwError(
node,
`'${kind}' declarations must be initialized.`,
);
}
if (node.name.kind !== SyntaxKind.Identifier) {
this.#throwError(
node.name,
`'${kind}' declarations may not have binding patterns.`,
);
}
}

const hasDeclareKeyword = hasModifier(
SyntaxKind.DeclareKeyword,
variableStatement,
);

// Definite assignment only allowed for non-declare let and var
if (
(hasDeclareKeyword ||
['await using', 'const', 'using'].includes(kind)) &&
hasExclamationToken
) {
this.#throwError(
node,
`A definite assignment assertion '!' is not permitted in this context.`,
);
}

if (
hasDeclareKeyword &&
node.initializer &&
(['let', 'var'].includes(kind) || node.type)
) {
this.#throwError(
node,
`Initializers are not permitted in ambient contexts.`,
);
}
// Theoretically, only certain initializers are allowed for declare const,
// (TS1254: A 'const' initializer in an ambient context must be a string
// or numeric literal or literal enum reference.) but we just allow
// all expressions

// Note! No-declare does not mean the variable is not ambient, because
// it can be further nested in other declare contexts. Therefore we cannot
// check for const initializers.
}
}

const init = this.convertChild(node.initializer);
const id = this.convertBindingNameWithTypeAnnotation(
node.name,
Expand All @@ -998,77 +1082,28 @@ export class Converter {
);
return this.createNode<TSESTree.VariableDeclarator>(node, {
type: AST_NODE_TYPES.VariableDeclarator,
definite,
definite: hasExclamationToken,
id,
init,
});
}

case SyntaxKind.VariableStatement: {
const result = this.createNode<TSESTree.VariableDeclaration>(node, {
type: AST_NODE_TYPES.VariableDeclaration,
declarations: this.convertChildren(node.declarationList.declarations),
declare: hasModifier(SyntaxKind.DeclareKeyword, node),
kind: getDeclarationKind(node.declarationList),
});
const declarations = node.declarationList.declarations;

if (!result.declarations.length) {
if (!declarations.length) {
this.#throwError(
node,
'A variable declaration list must have at least one variable declarator.',
);
}
if (result.kind === 'using' || result.kind === 'await using') {
node.declarationList.declarations.forEach((declaration, i) => {
if (result.declarations[i].init == null) {
this.#throwError(
declaration,
`'${result.kind}' declarations must be initialized.`,
);
}
if (result.declarations[i].id.type !== AST_NODE_TYPES.Identifier) {
this.#throwError(
declaration.name,
`'${result.kind}' declarations may not have binding patterns.`,
);
}
});
}
// Definite assignment only allowed for non-declare let and var
if (
result.declare ||
['await using', 'const', 'using'].includes(result.kind)
) {
node.declarationList.declarations.forEach((declaration, i) => {
if (result.declarations[i].definite) {
this.#throwError(
declaration,
`A definite assignment assertion '!' is not permitted in this context.`,
);
}
});
}
if (result.declare) {
node.declarationList.declarations.forEach((declaration, i) => {
if (
result.declarations[i].init &&
(['let', 'var'].includes(result.kind) ||
result.declarations[i].id.typeAnnotation)
) {
this.#throwError(
declaration,
`Initializers are not permitted in ambient contexts.`,
);
}
});
// Theoretically, only certain initializers are allowed for declare const,
// (TS1254: A 'const' initializer in an ambient context must be a string
// or numeric literal or literal enum reference.) but we just allow
// all expressions
}
// Note! No-declare does not mean the variable is not ambient, because
// it can be further nested in other declare contexts. Therefore we cannot
// check for const initializers.

const result = this.createNode<TSESTree.VariableDeclaration>(node, {
type: AST_NODE_TYPES.VariableDeclaration,
declarations: this.convertChildren(declarations),
declare: hasModifier(SyntaxKind.DeclareKeyword, node),
kind: getDeclarationKind(node.declarationList),
});

/**
* Semantically, decorators are not allowed on variable declarations,
Expand All @@ -1082,30 +1117,12 @@ export class Converter {

// mostly for for-of, for-in
case SyntaxKind.VariableDeclarationList: {
const result = this.createNode<TSESTree.VariableDeclaration>(node, {
return this.createNode<TSESTree.VariableDeclaration>(node, {
type: AST_NODE_TYPES.VariableDeclaration,
declarations: this.convertChildren(node.declarations),
declare: false,
kind: getDeclarationKind(node),
});

if (result.kind === 'using' || result.kind === 'await using') {
node.declarations.forEach((declaration, i) => {
if (result.declarations[i].init != null) {
this.#throwError(
declaration,
`'${result.kind}' declarations may not be initialized in for statement.`,
);
}
if (result.declarations[i].id.type !== AST_NODE_TYPES.Identifier) {
this.#throwError(
declaration.name,
`'${result.kind}' declarations may not have binding patterns.`,
);
}
});
}
return result;
}

// Expressions
Expand Down