Changed ArgumentError to DomainError for non-finite stepsize.

REQUIRE

@@ -1,5 +1,6 @@
 julia 0.6
 ArgCheck
+Compat
 DataStructures
 DiffResults
 DocStringExtensions

src/DynamicHMC.jl

@@ -5,6 +5,7 @@ import Base: rand, length, show
 import Base.LinAlg.checksquare
 
 using ArgCheck: @argcheck
+import Compat                   # for DomainError(val, msg) in v0.6
 using DataStructures
 using DiffResults: value, gradient
 using DocStringExtensions: SIGNATURES, FIELDS
@@ -381,7 +382,8 @@ Note that the ratio is not capped by `1`, so it is not a valid probability
 """
 function local_acceptance_ratio(H, z)
     target = neg_energy(H, z)
-    @argcheck isfinite(target) "Starting point has non-finite density."
+    isfinite(target) ||
+        throw(DomainError(z.p, "Starting point has non-finite density."))
     ϵ -> exp(neg_energy(H, leapfrog(H, z, ϵ)) - target)
 end
 

test/test-stepsize.jl

@@ -113,5 +113,5 @@ end
     p = InitialStepsizeSearch()
     H = Hamiltonian((x)->DiffResult(-Inf, ([0.0], )), GaussianKE(1))
     z = DynamicHMC.phasepoint_in(H, [1.0], [1.0])
-    @test_throws ArgumentError find_initial_stepsize(p, H, z)
+    @test_throws DomainError find_initial_stepsize(p, H, z)
 end