packages/babel-traverse/src/path/inference/inferers.js
import * as t from "@babel/types";
export { default as Identifier } from "./inferer-reference";
export function VariableDeclarator() {
const id = this.get("id");
if (!id.isIdentifier()) return;
const init = this.get("init");
let type = init.getTypeAnnotation();
if (type?.type === "AnyTypeAnnotation") {
// Detect "var foo = Array()" calls so we can optimize for arrays vs iterables.
if (
init.isCallExpression() &&
init.get("callee").isIdentifier({ name: "Array" }) &&
!init.scope.hasBinding("Array", true /* noGlobals */)
) {
type = ArrayExpression();
}
}
return type;
}
export function TypeCastExpression(node) {
return node.typeAnnotation;
}
TypeCastExpression.validParent = true;
export function NewExpression(node) {
if (this.get("callee").isIdentifier()) {
// only resolve identifier callee
return t.genericTypeAnnotation(node.callee);
}
}
export function TemplateLiteral() {
return t.stringTypeAnnotation();
}
export function UnaryExpression(node) {
const operator = node.operator;
if (operator === "void") {
return t.voidTypeAnnotation();
} else if (t.NUMBER_UNARY_OPERATORS.indexOf(operator) >= 0) {
return t.numberTypeAnnotation();
} else if (t.STRING_UNARY_OPERATORS.indexOf(operator) >= 0) {
return t.stringTypeAnnotation();
} else if (t.BOOLEAN_UNARY_OPERATORS.indexOf(operator) >= 0) {
return t.booleanTypeAnnotation();
}
}
export function BinaryExpression(node) {
const operator = node.operator;
if (t.NUMBER_BINARY_OPERATORS.indexOf(operator) >= 0) {
return t.numberTypeAnnotation();
} else if (t.BOOLEAN_BINARY_OPERATORS.indexOf(operator) >= 0) {
return t.booleanTypeAnnotation();
} else if (operator === "+") {
const right = this.get("right");
const left = this.get("left");
if (left.isBaseType("number") && right.isBaseType("number")) {
// both numbers so this will be a number
return t.numberTypeAnnotation();
} else if (left.isBaseType("string") || right.isBaseType("string")) {
// one is a string so the result will be a string
return t.stringTypeAnnotation();
}
// unsure if left and right are strings or numbers so stay on the safe side
return t.unionTypeAnnotation([
t.stringTypeAnnotation(),
t.numberTypeAnnotation(),
]);
}
}
export function LogicalExpression() {
const argumentTypes = [
this.get("left").getTypeAnnotation(),
this.get("right").getTypeAnnotation(),
];
if (t.isTSTypeAnnotation(argumentTypes[0]) && t.createTSUnionType) {
return t.createTSUnionType(argumentTypes);
}
if (t.createFlowUnionType) {
return t.createFlowUnionType(argumentTypes);
}
return t.createUnionTypeAnnotation(argumentTypes);
}
export function ConditionalExpression() {
const argumentTypes = [
this.get("consequent").getTypeAnnotation(),
this.get("alternate").getTypeAnnotation(),
];
if (t.isTSTypeAnnotation(argumentTypes[0]) && t.createTSUnionType) {
return t.createTSUnionType(argumentTypes);
}
if (t.createFlowUnionType) {
return t.createFlowUnionType(argumentTypes);
}
return t.createUnionTypeAnnotation(argumentTypes);
}
export function SequenceExpression() {
return this.get("expressions").pop().getTypeAnnotation();
}
export function ParenthesizedExpression() {
return this.get("expression").getTypeAnnotation();
}
export function AssignmentExpression() {
return this.get("right").getTypeAnnotation();
}
export function UpdateExpression(node) {
const operator = node.operator;
if (operator === "++" || operator === "--") {
return t.numberTypeAnnotation();
}
}
export function StringLiteral() {
return t.stringTypeAnnotation();
}
export function NumericLiteral() {
return t.numberTypeAnnotation();
}
export function BooleanLiteral() {
return t.booleanTypeAnnotation();
}
export function NullLiteral() {
return t.nullLiteralTypeAnnotation();
}
export function RegExpLiteral() {
return t.genericTypeAnnotation(t.identifier("RegExp"));
}
export function ObjectExpression() {
return t.genericTypeAnnotation(t.identifier("Object"));
}
export function ArrayExpression() {
return t.genericTypeAnnotation(t.identifier("Array"));
}
export function RestElement() {
return ArrayExpression();
}
RestElement.validParent = true;
function Func() {
return t.genericTypeAnnotation(t.identifier("Function"));
}
export {
Func as FunctionExpression,
Func as ArrowFunctionExpression,
Func as FunctionDeclaration,
Func as ClassExpression,
Func as ClassDeclaration,
};
const isArrayFrom = t.buildMatchMemberExpression("Array.from");
const isObjectKeys = t.buildMatchMemberExpression("Object.keys");
const isObjectValues = t.buildMatchMemberExpression("Object.values");
const isObjectEntries = t.buildMatchMemberExpression("Object.entries");
export function CallExpression() {
const { callee } = this.node;
if (isObjectKeys(callee)) {
return t.arrayTypeAnnotation(t.stringTypeAnnotation());
} else if (isArrayFrom(callee) || isObjectValues(callee)) {
return t.arrayTypeAnnotation(t.anyTypeAnnotation());
} else if (isObjectEntries(callee)) {
return t.arrayTypeAnnotation(
t.tupleTypeAnnotation([t.stringTypeAnnotation(), t.anyTypeAnnotation()]),
);
}
return resolveCall(this.get("callee"));
}
export function TaggedTemplateExpression() {
return resolveCall(this.get("tag"));
}
function resolveCall(callee) {
callee = callee.resolve();
if (callee.isFunction()) {
if (callee.is("async")) {
if (callee.is("generator")) {
return t.genericTypeAnnotation(t.identifier("AsyncIterator"));
} else {
return t.genericTypeAnnotation(t.identifier("Promise"));
}
} else {
if (callee.node.returnType) {
return callee.node.returnType;
} else {
// todo: get union type of all return arguments
}
}
}
}