Error if extrapolate-filling with a type, rather than value (fixes #232)

Author: timholy

src/extrapolation/filled.jl

@@ -8,6 +8,11 @@ function FilledExtrapolation(itp::AbstractInterpolation{T,N,IT}, fillvalue) wher
     FilledExtrapolation{Te,N,typeof(itp),IT,typeof(fillvalue)}(itp, fillvalue)
 end
 
+@noinline FilledExtrapolation(itp::AbstractInterpolation{T,N,IT}, ::Type{F}) where {T,N,IT,F} =
+    throw(ArgumentError("cannot create a filled extrapolation with a type $F, use a value of this type instead (e.g., $F(0))"))
+@noinline FilledExtrapolation(itp::AbstractInterpolation{T,N,IT}, ::Type{F}) where {T,N,IT,F<:BoundaryCondition} =
+    throw(ArgumentError("cannot create a filled extrapolation with a type $F, use a value of this type instead (e.g., $F())"))
+
 Base.parent(A::FilledExtrapolation) = A.itp
 etpflag(A::FilledExtrapolation) = A.fillvalue
 itpflag(A::FilledExtrapolation) = itpflag(A.itp)

test/extrapolation/runtests.jl

@@ -91,6 +91,10 @@ using Test
     @test itpe(10.1, 1) ≈ 10.1
     @test_throws BoundsError itpe(9.9, 0)
 
+    # Issue #232
+    targeterr = ArgumentError("cannot create a filled extrapolation with a type Line, use a value of this type instead (e.g., Line())")
+    @test_throws targeterr extrapolate(itp, Line)
+
     include("type-stability.jl")
     include("non1.jl")
 end