Avoid matching polyfilled global symbols.

Fix #22.

PiperOrigin-RevId: 352611340
Change-Id: I45ac167ee6f4fbea25feba0c91bcf940190e0aed

src/third_party/tsetse/util/absolute_matcher.ts

@@ -110,18 +110,27 @@ export class AbsoluteMatcher {
 
  debugLog(() => `start matching ${n.getText()} in ${p?.getText()}`);
 
- // Check if the node is being declared. Declaration may be imported without
- // programmer being aware of. We should not alert them about that.
- // Since import statments are also declarations, this have two notable
- // consequences.
- // - Match is negative for imports without renaming
- // - Match is positive for imports with renaming, when the imported name
- // is the target. Since Tsetse is flow insensitive and we don't track
- // symbol aliases, the import statement is the only place we can match
- // bad symbols if they get renamed.
- if (p && isAllowlistedNamedDeclaration(p) && p.name === n) {
- debugLog(() => `We don't flag symbol declarations`);
- return false;
+ if (p !== undefined) {
+ // Do not match global symbols appearing on the LHS of an assignment
+ // expression. This avoids false positives in polyfill code.
+ if (this.filePath === GLOBAL && ts.isBinaryExpression(p) &&
+ p.left === n && p.operatorToken.kind === ts.SyntaxKind.EqualsToken) {
+ return false;
+ }
+
+ // Check if the node is being declared. Declaration may be imported
+ // without programmer being aware of. We should not alert them about that.
+ // Since import statments are also declarations, this have two notable
+ // consequences.
+ // - Match is negative for imports without renaming
+ // - Match is positive for imports with renaming, when the imported name
+ // is the target. Since Tsetse is flow insensitive and we don't track
+ // symbol aliases, the import statement is the only place we can match
+ // bad symbols if they get renamed.
+ if (isAllowlistedNamedDeclaration(p) && p.name === n) {
+ debugLog(() => `We don't flag symbol declarations`);
+ return false;
+ }
  }
 
  // Get the symbol (or the one at the other end of this alias) that we're