Allow inference of recursion on a decreasing integer type parameter (#…

…26172)
JuliaLang · Feb 26, 2018 · 79c7bdd · 79c7bdd
1 parent d6edb86
commit 79c7bdd
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Showing 2 changed files with 6 additions and 1 deletion.
diff --git a/base/compiler/typelimits.jl b/base/compiler/typelimits.jl
@@ -256,7 +256,7 @@ function type_more_complex(@nospecialize(t), @nospecialize(c), sources::SimpleVe
         return type_more_complex(t, c.a, sources, depth, tupledepth, allowed_tuplelen) &&
                type_more_complex(t, c.b, sources, depth, tupledepth, allowed_tuplelen)
     elseif isa(t, Int) && isa(c, Int)
-        return t !== 1 # alternatively, could use !(0 <= t < c)
+        return t !== 1 && !(0 <= t < c) # alternatively, could use !(abs(t) <= abs(c) || abs(t) < n) for some n
     end
     # base case for data types
     if isa(t, DataType)

diff --git a/test/compiler/compiler.jl b/test/compiler/compiler.jl
@@ -1418,3 +1418,8 @@ function h25579(g)
 end
 @test Base.return_types(h25579, (Base.RefValue{Union{Nothing, Int}},)) ==
         Any[Union{Type{Float64}, Type{Int}, Type{Nothing}}]
+
+f26172(v) = Val{length(Base.tail(ntuple(identity, v)))}() # Val(M-1)
+g26172(::Val{0}) = ()
+g26172(v) = (nothing, g26172(f26172(v))...)
+@test @inferred(g26172(Val(10))) === ntuple(_ -> nothing, 10)