Tool to detect/display function dependencies in Rust crates

[pcwalton]

This would be useful for many things:

• Figuring out which functions are dead and can be removed.
• Visualize function dependencies (with dot).
• Be the basis for a Rust ccache workalike.
• On-demand, lazy unit tests.

[pcwalton]

I have call graph generation working in a branch.

[catamorphism]

@pcwalton did you ever integrate this?

[pcwalton]

No, it's assuredly bitrotted by now.

[catamorphism]

I'll take this on as a first step towards #2369

[catamorphism]

Bumping to 0.7.

[catamorphism]

Not critical for 0.7. Nominating for milestone 3, feature-complete.

[graydon]

just a bug, removing milestone/nomination.

[emberian]

Such a tool also needs to be able to tell me everywhere a type is used, for maximum utility. Since we have inference, it's near impossible to grep for a type or function returning that type to see where it's used.

[emberian]

Visiting for triage; nothing to add.