| Some environment variables affect rustc's behavior not because they are major compiler interfaces | |
| but rather because rustc is, ultimately, a Rust program, with debug logging, stack control, etc. | |
| Prefer to group tests that use environment variables to control something about rustc's core UX, | |
| like "can we parse this number of parens if we raise RUST_MIN_STACK?" with related code for that | |
| compiler feature. |