Mostly to avoid listing every internal package in kotlin-stdlib/kotlin-reflect, as in https://github.com/JetBrains/kotlin/blob/acd5b62148d797ffd24c4811d1d663f0c1ae7885/compiler/testData/diagnostics/testsWithUnsignedTypes/conversions/conversionOfSignedToUnsigned.txt#L144
Look into QUALIFIER for left-most "unrolled" qualified expression in CallExpressionResolver#getQualifiedExpressionTypeInfo. Drop some unused functions.