Fixup Nemocas#2196

Use `@inferred` correctly and fix return type

Author: joschmitt

src/generic/MPoly.jl

@@ -129,8 +129,12 @@ are given in the order of the variables for the ring, as supplied when the
 ring was created.
 """
 function exponent_vector(a::MPoly{T}, i::Int) where T <: RingElement
-   e = Vector{Int}(undef, nvars(parent(a)))
-   return exponent_vector!(e, a, i)
+  return exponent_vector(Vector{Int}, a, i)
+end
+
+function exponent_vector(::Type{Vector{S}}, a::MPoly{T}, i::Int) where {T <: RingElement, S}
+  e = Vector{S}(undef, nvars(parent(a)))
+  return exponent_vector!(e, a, i)
 end
 
 function exponent_vector!(e::Vector{S}, a::MPoly{T}, i::Int) where {T <: RingElement, S}
@@ -843,10 +847,10 @@ function Base.iterate(x::MPolyCoeffs, state::Union{Nothing, Int} = nothing)
    end
 end
 
-function Base.iterate(x::MPolyExponentVectors, state::Union{Nothing, Int} = nothing)
+function Base.iterate(x::MPolyExponentVectors{T, S}, state::Union{Nothing, Int} = nothing) where {T, S}
    s = isnothing(state) ? 1 : state + 1
    if length(x.poly) >= s
-      v = x.inplace ? exponent_vector!(x.temp, x.poly, s) : exponent_vector(x.poly, s)
+      v = x.inplace ? exponent_vector!(x.temp, x.poly, s) : exponent_vector(S, x.poly, s)
       return v, s
    else
       return nothing

test/generic/MPoly-test.jl

@@ -1882,15 +1882,15 @@ end
   R, (x, y, z) = polynomial_ring(QQ, [:x, :y, :z])
   f = x * y + 2 * x - 3 * z
 
-  @test @inferred collect(exponent_vectors(f)) == [[1, 1, 0], [1, 0, 0], [0, 0, 1]]
-  @test @inferred collect(exponent_vectors(Vector{UInt}, f)) == [UInt[1, 1, 0], UInt[1, 0, 0], UInt[0, 0, 1]]
-  @test @inferred collect(coefficients(f)) == [QQ(1), QQ(2), QQ(-3)]
-  @test @inferred collect(terms(f)) == [x * y, 2 * x, -3 * z]
-  @test @inferred collect(monomials(f)) == [x * y, x, z]
-
-  @test @inferred first(exponent_vectors(f, inplace = true)) == [1, 1, 0]
-  @test @inferred first(exponent_vectors(Vector{UInt}, f, inplace = true)) == UInt[1, 1, 0]
-  @test @inferred first(coefficients(f, inplace = true)) == QQ(1)
-  @test @inferred first(monomials(f, inplace = true)) == x * y
-  @test @inferred first(terms(f, inplace = true)) == x * y
+  @test (@inferred collect(exponent_vectors(f))) == [[1, 1, 0], [1, 0, 0], [0, 0, 1]]
+  @test (@inferred collect(exponent_vectors(Vector{UInt}, f))) == [UInt[1, 1, 0], UInt[1, 0, 0], UInt[0, 0, 1]]
+  @test (@inferred collect(coefficients(f))) == [QQ(1), QQ(2), QQ(-3)]
+  @test (@inferred collect(terms(f))) == [x * y, 2 * x, -3 * z]
+  @test (@inferred collect(monomials(f))) == [x * y, x, z]
+
+  @test (@inferred first(exponent_vectors(f, inplace = true))) == [1, 1, 0]
+  @test (@inferred first(exponent_vectors(Vector{UInt}, f, inplace = true))) == UInt[1, 1, 0]
+  @test (@inferred first(coefficients(f, inplace = true))) == QQ(1)
+  @test (@inferred first(monomials(f, inplace = true))) == x * y
+  @test (@inferred first(terms(f, inplace = true))) == x * y
 end