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Fix: Respect allowSyntheticDefaultImports for export specifiers from declaration files #62758

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Fix: Respect allowSyntheticDefaultImports for export specifiers from declaration files #62758

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Copilot Nov 14, 2025
7f69f3c
Fix: Respect allowSyntheticDefaultImports for export specifiers
Copilot Nov 14, 2025
d85f072
Fix: Only allow synthetic defaults for declaration files in export sp…
Copilot Nov 14, 2025
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8 changes: 7 additions & 1 deletion src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -3869,7 +3869,13 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
return exportDefaultSymbol;
}
const hasDefaultOnly = isOnlyImportableAsDefault(specifier, moduleSymbol);
const hasSyntheticDefault = canHaveSyntheticDefault(file, moduleSymbol, dontResolveAlias, specifier);
let hasSyntheticDefault = canHaveSyntheticDefault(file, moduleSymbol, dontResolveAlias, specifier);
// For export specifiers re-exporting 'default' from declaration files, when allowSyntheticDefaultImports
// is enabled, allow synthetic default. Declaration files may correspond to CommonJS modules at runtime,
// where a default import is allowed to reference the whole module.exports symbol.
if (!hasSyntheticDefault && isExportSpecifier(node) && allowSyntheticDefaultImports && (!file || file.isDeclarationFile)) {
hasSyntheticDefault = true;
}
if (!exportDefaultSymbol && !hasSyntheticDefault && !hasDefaultOnly) {
if (hasExportAssignmentSymbol(moduleSymbol) && !allowSyntheticDefaultImports) {
const compilerOptionName = moduleKind >= ModuleKind.ES2015 ? "allowSyntheticDefaultImports" : "esModuleInterop";
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