Overloading Base.hash is 2x slower than an identical function

General Usage Performance
2

Ah. Interpolating is the cause:

julia> @benchmark Base.hash($b, UInt64(0))
BenchmarkTools.Trial: 
  memory estimate:  0 bytes
  allocs estimate:  0
  --------------
  minimum time:     8.727 ns (0.00% GC)
  median time:      8.989 ns (0.00% GC)
  mean time:        9.292 ns (0.00% GC)
  maximum time:     89.672 ns (0.00% GC)
  --------------
  samples:          10000
  evals/sample:     999

julia> @benchmark Base_hash($b, UInt64(0))
BenchmarkTools.Trial: 
  memory estimate:  0 bytes
  allocs estimate:  0
  --------------
  minimum time:     8.727 ns (0.00% GC)
  median time:      8.778 ns (0.00% GC)
  mean time:        9.336 ns (0.00% GC)
  maximum time:     71.057 ns (0.00% GC)
  --------------
  samples:          10000
  evals/sample:     999