RUST_LOG matches prefix

[sanxiyn]

This seems to be by design, but this doesn't seem to allow enabling logging only for rustc::middle::ty without enabling it for rustc::middle::typeck. Or is this possible?

[graydon]

It is not presently possible. The current behavior is intentional but we should probably revisit it. relative of #2038 and a sub-bug of #3309

[huonw]

Triage: nothing to add. Similar to #6032.

[alexcrichton]

Closing in favor of #6032. The outcome of that issue will dicate whether this behavior is valid or not.