Try   HackMD

Inject doctests into host crate

Idea by @Urgau.
Tracking issue: #141083.

Motivation

  • Have doctest work in binary crate
  • Have better warnings and errors reporting by having correct spans
  • Handle doctests with different editions in the same compilation unit
  • Simplify cross-compilation (deprecating all the doctest-cross-arg )

Implementation

  • Have a hook in the AST->HIR lowering that is only implemented by rustdoc:
    • It would parse the doctests, create the AST nodes (by calling rustc_parse maybe?) and give back to rustc the AST nodes corresponding to #[test] fn doctest_1234 { ... } with the doctest body inside
  • Rustdoc would give spans corresponding to the original doctest code in the doc comment. This could include a different edition for doctests that override that
    • Problem: how would we get the spans to be correct given the presence of /// in the original code but not the new code given to rustc_parse? would it just work or does it need more invasive changes?
  • These AST nodes would then be injected into the crate and lowered into HIR and go through the rest of the compilation
  • Then we run them using the libtest harness.
  • We need to run all rustc passes to make it work