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scope.js
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scope.js
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// @flow
import {
SCOPE_ARROW,
SCOPE_ASYNC,
SCOPE_DIRECT_SUPER,
SCOPE_FUNCTION,
SCOPE_GENERATOR,
SCOPE_SIMPLE_CATCH,
SCOPE_SUPER,
SCOPE_PROGRAM,
SCOPE_VAR,
SCOPE_CLASS,
BIND_SCOPE_FUNCTION,
BIND_SCOPE_VAR,
BIND_SCOPE_LEXICAL,
BIND_KIND_VALUE,
type ScopeFlags,
type BindingTypes,
} from "./scopeflags";
import * as N from "../types";
// Start an AST node, attaching a start offset.
export class Scope {
flags: ScopeFlags;
// A list of var-declared names in the current lexical scope
var: string[] = [];
// A list of lexically-declared names in the current lexical scope
lexical: string[] = [];
// A list of lexically-declared FunctionDeclaration names in the current lexical scope
functions: string[] = [];
constructor(flags: ScopeFlags) {
this.flags = flags;
}
}
type raiseFunction = (number, string) => void;
// The functions in this module keep track of declared variables in the
// current scope in order to detect duplicate variable names.
export default class ScopeHandler<IScope: Scope = Scope> {
scopeStack: Array<IScope> = [];
raise: raiseFunction;
inModule: boolean;
undefinedExports: Map<string, number> = new Map();
undefinedPrivateNames: Map<string, number> = new Map();
constructor(raise: raiseFunction, inModule: boolean) {
this.raise = raise;
this.inModule = inModule;
}
get inFunction() {
return (this.currentVarScope().flags & SCOPE_FUNCTION) > 0;
}
get inGenerator() {
return (this.currentVarScope().flags & SCOPE_GENERATOR) > 0;
}
// the following loop always exit because SCOPE_PROGRAM is SCOPE_VAR
// $FlowIgnore
get inAsync() {
for (let i = this.scopeStack.length - 1; ; i--) {
const scope = this.scopeStack[i];
const isVarScope = scope.flags & SCOPE_VAR;
const isClassScope = scope.flags & SCOPE_CLASS;
if (isClassScope && !isVarScope) {
// If it meets a class scope before a var scope, it means it is a class property initializer
// which does not have an [Await] parameter in its grammar
return false;
} else if (isVarScope) {
return (scope.flags & SCOPE_ASYNC) > 0;
}
}
}
get allowSuper() {
return (this.currentThisScope().flags & SCOPE_SUPER) > 0;
}
get allowDirectSuper() {
return (this.currentThisScope().flags & SCOPE_DIRECT_SUPER) > 0;
}
get inClass() {
return (this.currentThisScope().flags & SCOPE_CLASS) > 0;
}
get inNonArrowFunction() {
return (this.currentThisScope().flags & SCOPE_FUNCTION) > 0;
}
get treatFunctionsAsVar() {
return this.treatFunctionsAsVarInScope(this.currentScope());
}
createScope(flags: ScopeFlags): Scope {
return new Scope(flags);
}
// This method will be overwritten by subclasses
/*:: +createScope: (flags: ScopeFlags) => IScope; */
enter(flags: ScopeFlags) {
this.scopeStack.push(this.createScope(flags));
}
exit() {
this.scopeStack.pop();
}
// The spec says:
// > At the top level of a function, or script, function declarations are
// > treated like var declarations rather than like lexical declarations.
treatFunctionsAsVarInScope(scope: IScope): boolean {
return !!(
scope.flags & SCOPE_FUNCTION ||
(!this.inModule && scope.flags & SCOPE_PROGRAM)
);
}
declareName(name: string, bindingType: BindingTypes, pos: number) {
let scope = this.currentScope();
if (bindingType & BIND_SCOPE_LEXICAL || bindingType & BIND_SCOPE_FUNCTION) {
this.checkRedeclarationInScope(scope, name, bindingType, pos);
if (bindingType & BIND_SCOPE_FUNCTION) {
scope.functions.push(name);
} else {
scope.lexical.push(name);
}
if (bindingType & BIND_SCOPE_LEXICAL) {
this.maybeExportDefined(scope, name);
}
} else if (bindingType & BIND_SCOPE_VAR) {
for (let i = this.scopeStack.length - 1; i >= 0; --i) {
scope = this.scopeStack[i];
this.checkRedeclarationInScope(scope, name, bindingType, pos);
scope.var.push(name);
this.maybeExportDefined(scope, name);
if (scope.flags & SCOPE_VAR) break;
}
}
if (this.inModule && scope.flags & SCOPE_PROGRAM) {
this.undefinedExports.delete(name);
}
}
maybeExportDefined(scope: IScope, name: string) {
if (this.inModule && scope.flags & SCOPE_PROGRAM) {
this.undefinedExports.delete(name);
}
}
checkRedeclarationInScope(
scope: IScope,
name: string,
bindingType: BindingTypes,
pos: number,
) {
if (this.isRedeclaredInScope(scope, name, bindingType)) {
this.raise(pos, `Identifier '${name}' has already been declared`);
}
}
isRedeclaredInScope(
scope: IScope,
name: string,
bindingType: BindingTypes,
): boolean {
if (!(bindingType & BIND_KIND_VALUE)) return false;
if (bindingType & BIND_SCOPE_LEXICAL) {
return (
scope.lexical.indexOf(name) > -1 ||
scope.functions.indexOf(name) > -1 ||
scope.var.indexOf(name) > -1
);
}
if (bindingType & BIND_SCOPE_FUNCTION) {
return (
scope.lexical.indexOf(name) > -1 ||
(!this.treatFunctionsAsVarInScope(scope) &&
scope.var.indexOf(name) > -1)
);
}
return (
(scope.lexical.indexOf(name) > -1 &&
!(scope.flags & SCOPE_SIMPLE_CATCH && scope.lexical[0] === name)) ||
(!this.treatFunctionsAsVarInScope(scope) &&
scope.functions.indexOf(name) > -1)
);
}
checkLocalExport(id: N.Identifier) {
if (
this.scopeStack[0].lexical.indexOf(id.name) === -1 &&
this.scopeStack[0].var.indexOf(id.name) === -1 &&
// In strict mode, scope.functions will always be empty.
// Modules are strict by default, but the `scriptMode` option
// can overwrite this behavior.
this.scopeStack[0].functions.indexOf(id.name) === -1
) {
this.undefinedExports.set(id.name, id.start);
}
}
currentScope(): IScope {
return this.scopeStack[this.scopeStack.length - 1];
}
// $FlowIgnore
currentVarScope(): IScope {
for (let i = this.scopeStack.length - 1; ; i--) {
const scope = this.scopeStack[i];
if (scope.flags & SCOPE_VAR) {
return scope;
}
}
}
// Could be useful for `arguments`, `this`, `new.target`, `super()`, `super.property`, and `super[property]`.
// $FlowIgnore
currentThisScope(): IScope {
for (let i = this.scopeStack.length - 1; ; i--) {
const scope = this.scopeStack[i];
if (
(scope.flags & SCOPE_VAR || scope.flags & SCOPE_CLASS) &&
!(scope.flags & SCOPE_ARROW)
) {
return scope;
}
}
}
}