Bad documentation for --emit-llvm and --save-temps compiler flags

[catamorphism]

Today I learned:

• --emit-llvm silently does nothing if you're compiling to an executable, and requires that you provide a -o filename that ends in .bc. Perhaps there should be errors instead.
• --save-temps and --emit-llvm only do anything if they come before the crate file name.

These things should probably be documented. I'm not sure where such documentation belongs (seems a bit verbose for the command-line usage notes).

[catamorphism]

Not critical for 0.6, de-milestoning.

[metajack]

Nominating for well covered.

[graydon]

accepted for production-ready milestone

[brson]

cc #7791

[pnkfelix]

probably subsumed by #7791. But tagging 1.0 to ensure it gets fixed one way or another. P-high.

[lucab]

I believe this has been closed in the above bug/PR:

$ rustc -v
 rustc 0.10-pre (0cc8ba0 2014-02-19 21:56:51 -0800)
 host: x86_64-unknown-linux-gnu
$ rustc --emit=ir mainpage.rs
$ ls
 mainpage.ll  mainpage.rs
$ rustc -C save-temps mainpage.rs 
$ ls
 mainpage  mainpage.bc  mainpage.metadata.o  mainpage.no-opt.bc  mainpage.o  mainpage.rs

Can anybody close it?

[alexcrichton]

Indeed, closed by 6e7968b (we even have dox in the manpage!)