map(a -> zip(a...), itr) inference imprecision

[tpapp]

julia> versioninfo()
Julia Version 1.3.0-rc4.1
Commit 8c4656b97a (2019-10-15 14:08 UTC)
Platform Info:
  OS: Linux (x86_64-linux-gnu)
  CPU: Intel(R) Core(TM) i5-8250U CPU @ 1.60GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.1 (ORCJIT, skylake)
Environment:
  JULIA_CMDSTAN_HOME = /home/tamas/src/cmdstan/

MWE condensed from discussion:

using Test

# wrapper is pretty much irrelevant for the problem, just to make an MWE
@inline wrapper(itrs) = sum(prod(first.(i)) for i in Iterators.product(itrs...))

zipped1(pairs) = wrapper(map(pair -> zip(pair...), pairs))

zipped2(pairs) = wrapper(map(pair -> zip(pair[1], pair[2]), pairs))

pairs = (1:5 => 1:5, 2:3 => 2:3)

@inferred zipped1(pairs) # ERROR: return type Int64 does not match inferred return type Any
@inferred zipped2(pairs) # inferred correctly

I found some similar-looking issues, but this did not look like a duplicate of any of them.

[vtjnash]

Duplicate of #29114

[Keno]

This wasn't quite a duplicate of #29114 (which was mostly about inlining not inference). But in any case, it got fixed by the recent inference precision enhancements.

[tpapp]

Indeed, it is fixed now. Thanks for the clarification.