99 lines
2.9 KiB
JavaScript
99 lines
2.9 KiB
JavaScript
import {
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isBlockScopedDeclaration,
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isFunctionScopedDeclaration,
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isNonTopLevelDeclaration,
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} from "./parser/tokenizer";
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import {TokenType as tt} from "./parser/tokenizer/types";
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/**
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* Traverse the given tokens and modify them if necessary to indicate that some names shadow global
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* variables.
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*/
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export default function identifyShadowedGlobals(
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tokens,
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scopes,
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globalNames,
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) {
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if (!hasShadowedGlobals(tokens, globalNames)) {
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return;
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}
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markShadowedGlobals(tokens, scopes, globalNames);
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}
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/**
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* We can do a fast up-front check to see if there are any declarations to global names. If not,
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* then there's no point in computing scope assignments.
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*/
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// Exported for testing.
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export function hasShadowedGlobals(tokens, globalNames) {
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for (const token of tokens.tokens) {
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if (
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token.type === tt.name &&
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!token.isType &&
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isNonTopLevelDeclaration(token) &&
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globalNames.has(tokens.identifierNameForToken(token))
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) {
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return true;
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}
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}
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return false;
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}
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function markShadowedGlobals(
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tokens,
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scopes,
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globalNames,
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) {
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const scopeStack = [];
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let scopeIndex = scopes.length - 1;
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// Scopes were generated at completion time, so they're sorted by end index, so we can maintain a
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// good stack by going backwards through them.
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for (let i = tokens.tokens.length - 1; ; i--) {
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while (scopeStack.length > 0 && scopeStack[scopeStack.length - 1].startTokenIndex === i + 1) {
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scopeStack.pop();
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}
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while (scopeIndex >= 0 && scopes[scopeIndex].endTokenIndex === i + 1) {
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scopeStack.push(scopes[scopeIndex]);
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scopeIndex--;
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}
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// Process scopes after the last iteration so we can make sure we pop all of them.
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if (i < 0) {
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break;
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}
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const token = tokens.tokens[i];
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const name = tokens.identifierNameForToken(token);
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if (scopeStack.length > 1 && !token.isType && token.type === tt.name && globalNames.has(name)) {
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if (isBlockScopedDeclaration(token)) {
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markShadowedForScope(scopeStack[scopeStack.length - 1], tokens, name);
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} else if (isFunctionScopedDeclaration(token)) {
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let stackIndex = scopeStack.length - 1;
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while (stackIndex > 0 && !scopeStack[stackIndex].isFunctionScope) {
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stackIndex--;
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}
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if (stackIndex < 0) {
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throw new Error("Did not find parent function scope.");
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}
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markShadowedForScope(scopeStack[stackIndex], tokens, name);
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}
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}
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}
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if (scopeStack.length > 0) {
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throw new Error("Expected empty scope stack after processing file.");
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}
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}
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function markShadowedForScope(scope, tokens, name) {
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for (let i = scope.startTokenIndex; i < scope.endTokenIndex; i++) {
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const token = tokens.tokens[i];
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if (
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(token.type === tt.name || token.type === tt.jsxName) &&
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tokens.identifierNameForToken(token) === name
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) {
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token.shadowsGlobal = true;
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}
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}
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}
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