Function rustc_query_impl::make_query::param_env

pub fn param_env<'tcx>(
    tcx: QueryCtxt<'tcx>, 
    key: param_env<'tcx>
) -> QueryStackFrame

Gets the ParameterEnvironment for a given item; this environment will be in “user-facing” mode, meaning that it is suitable for type-checking etc, and it does not normalize specializable associated types. This is almost always what you want, unless you are doing MIR optimizations, in which case you might want to use reveal_all() method to change modes.