Please do not do this without actually making the per-function timing data a more user-friendly feature. It's hidden behind -Xfrontend because it was meant as a debugging option for us; it is not considered a supported feature of the compiler.

(In particular, there are a number of things that this timing data does not include that it should, including initial value expressions for properties.)

Sounds like a useful feature but we will absolutely need to coordinate this with the compiler (and not just expose what happens to be available there now without coordination).

Comment by Andrew Bennett (JIRA)

@belkadan I couldn't find a ticket for this on the compiler, do you know if there is one? It'd be nice to have a more complete wish-list for this feature 🙂

You mention on one commit:

• Other parts of type-checking not measured by this may also be slow.

• May include first-use penalties (i.e. "this is slow because it's
  the first function that references an imported type, which causes
  many things to be imported")

• Does not report anything whatsoever about other phases of compilation
  (SILGen, optimization, IRGen, assembly emission, whatever).

• Does not catch anything accidentally being type-checked multiple times
  (a known issue for initial value expressions on properties).

In case anyone decides to take a look at it, I've added some notes after a brief look myself:

This function seems to be the guts of the current implementation:
https://github.com/apple/swift/blob/master/lib/Sema/TypeCheckStmt.cpp#L147

Also worth looking at:

-debug-time-function-bodies: dump time spent type-checking each function
apple/swift@8612e24

Add frontend option "-warn-long-function-bodies=<N>".
apple/swift@18c7592