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Fix case where getParameterTypeAtPosition didn't return undefined for out of bounds

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This commit is contained in:
Anders Hejlsberg
2019-03-09 06:55:14 -08:00
parent 97fbc87e98
commit fcc2d22cf5
1 changed files with 7 additions and 2 deletions
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9
src/compiler/checker.ts
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@@ -21770,9 +21770,14 @@ namespace ts {
return getTypeOfParameter(signature.parameters[pos]);
}
if (signature.hasRestParameter) {
// We want to return the value undefined for an out of bounds parameter position,
// so we need to check bounds here before calling getIndexedAccessType (which
// otherwise would return the type 'undefined').
const restType = getTypeOfSymbol(signature.parameters[paramCount]);
const indexType = getLiteralType(pos - paramCount);
return getIndexedAccessType(restType, indexType);
const index = pos - paramCount;
if (!isTupleType(restType) || restType.target.hasRestElement || index < (restType.typeArguments || emptyArray).length) {
return getIndexedAccessType(restType, getLiteralType(index));
}
}
return undefined;
}