Copying notes from parent issue:
unboxedType
spec: IAE when the "given type has no unboxing conversion"
actual: matches spec
expected: fine, but could be more explicit that there will always be an IAE for non-DeclaredTypes.
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getWildcardType
spec: IAE if an input TypeMirror is "not valid"
actual: IAE for PrimitiveType, WildcardType, UnionType, ExecutableType, and NoTypes; no error for ErrorTypes.
expected: behavior is fine, but spec should be more clear -- that is, IAE for all non-ReferenceTypes.