In order to only check if a program is well-formed (think cargo check), one would like to call rustc without emitting any files. cargo check uses --emit=metadata -Z no-codegen because the metadata is needed to check dependent crates.

However, it seems like it's impossible to tell the compiler to not write any files in the case of --crate-type=lib. For the default --crate-type=bin it works: rustc -Z no-codegen foo.rs does not emit any files. But again, for rustc -Z no-codegen --crate-type=lib foo.rs it emits an .rlib file.

In case this isn't a bug, would it be possible to add an --emit=nothing or equivalent option?

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