address review comments and more tests

Author: rfourquet

src/Primes.jl

@@ -531,7 +531,7 @@ end
 
 # add: checked add (when makes sense), result of same type as first argument
 
-add(n::BigInt, x::Int) = n+x
+add(n::BigInt, x::Int) = n + x
 add(n::Integer, x::Int) = Base.checked_add(n, oftype(n, x))
 
 # add_! : "may" mutate the Integer argument (only for BigInt currently)
@@ -723,13 +723,14 @@ struct PrevPrimes{T<:Integer}
     start::T
 end
 
-iterate(np::PrevPrimes, state=np.start) =
+function iterate(np::PrevPrimes, state=np.start)
     if isone(state)
         nothing
     else
         p = prevprime(state)
         (p, p-one(p))
     end
+end
 
 IteratorSize(::Type{<:PrevPrimes}) = Base.SizeUnknown()
 IteratorEltype(::Type{<:PrevPrimes}) = Base.HasEltype()

test/runtests.jl

@@ -407,6 +407,9 @@ end
     @test nextprimes(4, 1)[1] == nextprimes(5, 1)[1] == 5
     @test eltype(nextprimes(10)) == Int
     @test eltype(nextprimes(big(10))) == BigInt
+    @test Base.IteratorEltype(nextprimes(10)) == Base.HasEltype()
+    @test Base.IteratorSize(nextprimes(10)) == Base.IsInfinite()
+
 end
 
 
@@ -419,6 +422,7 @@ end
     @test prevprimes(6, 1)[1] == prevprimes(5, 1)[1] == 5
     @test prevprimes(4, 1)[1] == prevprimes(3, 1)[1] == 3
     @test prevprimes(2, 1)[1] == 2
+    @test isempty(prevprimes(1, 1))
     let p8 = collect(prevprimes(typemax(Int8)))
         @test length(p8) == 31
         @test p8[end] == 2
@@ -427,4 +431,6 @@ end
     end
     @test eltype(prevprimes(10)) == Int
     @test eltype(prevprimes(big(10))) == BigInt
+    @test Base.IteratorEltype(prevprimes(10)) == Base.HasEltype()
+    @test Base.IteratorSize(prevprimes(10)) == Base.SizeUnknown()
 end