doctests marked with 'no_run' permit ICEs

[frewsxcv]

irc discussion: https://botbot.me/mozilla/rust-docs/2018-03-30/?msg=98430464&page=1

run this example: https://doc.rust-lang.org/nightly/std/fs/fn.read_string.html

at the time of writing it ICEs, but doctests don't catch it because it's marked no_run

[ollie27]

rustdoc stops compilation after analysis for no_run

rust/src/librustdoc/test.rs

Lines 261 to 263 in f1c21b0

	if no_run {
	control.after_analysis.stop = Compilation::Stop;
	}

and that ICE looks like it's happening during trans.

[QuietMisdreavus]

@rust-lang/rustdoc What do y'all think? Should we try to compile no_run doctests to completion, or is this issue moot?

[GuillaumeGomez]

Sounds weird. no_run should check the whole code but I don't see the point to generate any binary.

[jyn514]

I don't see much point in compiling these. The tradeoff "you occasionally discover bugs in the compiler and can't run your tests" doesn't seem worth "your tests always take longer to run".

[jyn514]

@Manishearth suggested adding an attribute that means "compile fully, but don't run" (e.g. build).