close issue #395; allow symbol to be passed as Val(:x) (#398)

* close issue #395; allow symbol to be passed as Val(:x)

* varsymbol approach

* take II

* keep bad formatting, fix later

Project.toml

@@ -2,7 +2,7 @@ name = "Polynomials"
 uuid = "f27b6e38-b328-58d1-80ce-0feddd5e7a45"
 license = "MIT"
 author = "JuliaMath"
-version = "2.0.24"
+version = "2.0.25"
 
 [deps]
 Intervals = "d8418881-c3e1-53bb-8760-2df7ec849ed5"

src/abstract.jl

@@ -1,8 +1,12 @@
 export AbstractPolynomial
 
 
+# *internal* means to pass variable symbol to constructor through 2nd position and keep type stability
+struct Var{T} end
+Var(x::Symbol) = Var{x}()
+Symbol(::Var{T}) where {T} = T
 
-const SymbolLike = Union{AbstractString,Char,Symbol}
+const SymbolLike = Union{AbstractString,Char,Symbol, Var{T} where T}
 
 """
     AbstractPolynomial{T,X}
@@ -51,7 +55,7 @@ abstract type AbstractPolynomial{T,X} end
 
 # convert `as` into polynomial of type P based on instance, inheriting variable
 # (and for LaurentPolynomial the offset)
-_convert(p::P, as) where {T,X,P <: AbstractPolynomial{T,X}} = ⟒(P)(as, X)
+_convert(p::P, as) where {T,X,P <: AbstractPolynomial{T,X}} = ⟒(P)(as, Var(X))
 
 
 """
@@ -122,7 +126,7 @@ macro registerN(name, params...)
             $poly{$(αs...),promote_type(T,S),X}
 
         function $poly{$(αs...),T}(x::AbstractVector{S}, var::SymbolLike = :x) where {$(αs...),T,S}
-            $poly{$(αs...),T, Symbol(var)}(T.(x))
+            $poly{$(αs...),T,Symbol(var)}(T.(x))
         end
         $poly{$(αs...)}(coeffs::AbstractVector{T}, var::SymbolLike=:x) where {$(αs...),T} =
             $poly{$(αs...),T,Symbol(var)}(coeffs)

src/polynomials/Poly.jl

@@ -3,6 +3,7 @@ module PolyCompat
 using ..Polynomials
 indeterminate = Polynomials.indeterminate
 
+
 #=
 Compat support for old code. This will be opt-in by v1.0, through "using Polynomials.PolyCompat"
 =#

test/StandardBasis.jl

@@ -57,6 +57,10 @@ isimmutable(::Type{<:ImmutablePolynomial}) = true
         @test_throws InexactError P{Int}([1+im, 1], :x)
         @test_throws InexactError P{Int,:x}(1+im)
         @test_throws InexactError P{Int}(1+im)
+
+        ## issue #395
+        v = [1,2,3]
+        @test P(v) == P(v,:x) == P(v,'x') == P(v,"x") == P(v, Polynomials.Var(:x))
     end
 
 end
@@ -393,9 +397,10 @@ end
         pN = P([276,3,87,15,24,0])
         pR = P([3 // 4, -2 // 1, 1 // 1])
 
-        # type stability of the default constructor without variable name
+        # type stability of the default constructor with/without variable name
         if P !== ImmutablePolynomial
             @inferred P([1, 2, 3])
+            @inferred P([1,2,3], Polynomials.Var(:x))
         end
 
         @test p3 == P([1,2,1])
@@ -450,6 +455,11 @@ end
     x = variable(LaurentPolynomial)
     @test Polynomials.isconstant(x * inv(x))
     @test_throws ArgumentError inv(x + x^2)
+
+    # issue #395
+    p = Polynomial([2,1], :s)
+    @inferred -p # issue #395
+
 end
 
 @testset "Divrem" begin