fix an edge constructor bug in LinearIndices (#37928)

Author: johnnychen94

base/indices.jl

@@ -451,11 +451,13 @@ end
 LinearIndices(::Tuple{}) = LinearIndices{0,typeof(())}(())
 LinearIndices(inds::NTuple{N,AbstractUnitRange{<:Integer}}) where {N} =
     LinearIndices(map(r->convert(AbstractUnitRange{Int}, r), inds))
-LinearIndices(sz::NTuple{N,<:Integer}) where {N} = LinearIndices(map(Base.OneTo, sz))
 LinearIndices(inds::NTuple{N,Union{<:Integer,AbstractUnitRange{<:Integer}}}) where {N} =
-    LinearIndices(map(i->first(i):last(i), inds))
+    LinearIndices(map(_convert2ind, inds))
 LinearIndices(A::Union{AbstractArray,SimpleVector}) = LinearIndices(axes(A))
 
+_convert2ind(i::Integer) = Base.OneTo(i)
+_convert2ind(ind::AbstractUnitRange) = first(ind):last(ind)
+
 promote_rule(::Type{LinearIndices{N,R1}}, ::Type{LinearIndices{N,R2}}) where {N,R1,R2} =
     LinearIndices{N,indices_promote_type(R1,R2)}
 

test/abstractarray.jl

@@ -225,6 +225,58 @@ end
     end
 end
 
+@testset "LinearIndices" begin
+    @testset "constructors" begin
+        for oinds in [
+            (2, 3),
+            (UInt8(2), 3),
+            (2, UInt8(3)),
+            (2, 1:3),
+            (Base.OneTo(2), 1:3)
+        ]
+            R = LinearIndices(oinds)
+            @test size(R) == (2, 3)
+            @test axes(R) == (Base.OneTo(2), Base.OneTo(3))
+            @test R[begin] == 1
+            @test R[end] == 6
+        end
+
+        for oinds in [(2, ), (2, 3), (2, 3, 4)]
+            R = CartesianIndices(oinds)
+            @test size(R) == oinds
+        end
+    end
+
+    @testset "IdentityUnitRange" begin
+        function _collect(A)
+            rst = eltype(A)[]
+            for i in A
+                push!(rst, i)
+            end
+            rst
+        end
+        function _simd_collect(A)
+            rst = eltype(A)[]
+            @simd for i in A
+                push!(rst, i)
+            end
+            rst
+        end
+
+        for oinds in [
+            (Base.IdentityUnitRange(0:1),),
+            (Base.IdentityUnitRange(0:1), Base.IdentityUnitRange(0:2)),
+            (Base.IdentityUnitRange(0:1), Base.OneTo(3)),
+        ]
+            R = LinearIndices(oinds)
+            @test axes(R) === oinds
+            @test _collect(R) == _simd_collect(R) == vec(collect(R))
+        end
+        R = LinearIndices((Base.IdentityUnitRange(0:1), 0:1))
+        @test axes(R) == (Base.IdentityUnitRange(0:1), Base.OneTo(2))
+    end
+end
+
 # token type on which to dispatch testing methods in order to avoid potential
 # name conflicts elsewhere in the base test suite
 mutable struct TestAbstractArray end