make ntuple(f, Val{-1}) throw ArgumentError

otherwise Julia would stuck in an endless type inference loop (cherry picked from commit 2b4bb1a) ref #21697
JuliaLang · May 15, 2017 · 91d0f09 · 91d0f09
1 parent d13f3e9
commit 91d0f09
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diff --git a/base/tuple.jl b/base/tuple.jl
@@ -142,6 +142,7 @@ ntuple(f, ::Type{Val{15}}) = (@_inline_meta; (f(1), f(2), f(3), f(4), f(5), f(6)
 
 function ntuple(f::F, ::Type{Val{N}}) where {F,N}
     Core.typeassert(N, Int)
+    (N >= 0) || throw(ArgumentError(string("tuple length should be ≥0, got ", N)))
     _ntuple((), f, Val{N})
 end
 

diff --git a/test/tuple.jl b/test/tuple.jl
@@ -168,6 +168,8 @@ end
 @test @inferred(ntuple(abs2, Val{4})) == (1, 4, 9, 16)
 @test @inferred(ntuple(abs2, Val{5})) == (1, 4, 9, 16, 25)
 @test @inferred(ntuple(abs2, Val{6})) == (1, 4, 9, 16, 25, 36)
+# issue #21697
+@test_throws ArgumentError ntuple(abs2, Val{-1})
 
 # issue #12854
 @test_throws TypeError ntuple(identity, Val{1:2})