From d3964b600a5e596bd47cf04b3da4a1e78d4aecaf Mon Sep 17 00:00:00 2001
From: Neven Sajko <4944410+nsajko@users.noreply.github.com>
Date: Fri, 10 Jan 2025 10:00:22 +0100
Subject: [PATCH] broadcast: align `ndims` implementation with intent behind
 code (#56999)

The `N<:Integer` constraint was nonsensical, given that `(N === Any) ||
(N isa Int)`. N5N3 noticed this back in 2022:
https://github.com/JuliaLang/julia/pull/44061#discussion_r883261337

Follow up on #44061. Also xref #45477.
---
 base/broadcast.jl | 9 +++++++--
 test/broadcast.jl | 2 ++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/base/broadcast.jl b/base/broadcast.jl
index 7f278fc1ca66f..512b397352040 100644
--- a/base/broadcast.jl
+++ b/base/broadcast.jl
@@ -280,9 +280,14 @@ Base.@propagate_inbounds function Base.iterate(bc::Broadcasted, s)
 end
 
 Base.IteratorSize(::Type{T}) where {T<:Broadcasted} = Base.HasShape{ndims(T)}()
-Base.ndims(BC::Type{<:Broadcasted{<:Any,Nothing}}) = _maxndims(fieldtype(BC, :args))
-Base.ndims(::Type{<:Broadcasted{<:AbstractArrayStyle{N},Nothing}}) where {N<:Integer} = N
+Base.ndims(BC::Type{<:Broadcasted{<:Any,Nothing}}) = _maxndims_broadcasted(BC)
+# the `AbstractArrayStyle` type parameter is required to be either equal to `Any` or be an `Int` value
+Base.ndims(BC::Type{<:Broadcasted{<:AbstractArrayStyle{Any},Nothing}}) = _maxndims_broadcasted(BC)
+Base.ndims(::Type{<:Broadcasted{<:AbstractArrayStyle{N},Nothing}}) where {N} = N::Int
 
+function _maxndims_broadcasted(BC::Type{<:Broadcasted})
+    _maxndims(fieldtype(BC, :args))
+end
 _maxndims(::Type{T}) where {T<:Tuple} = reduce(max, ntuple(n -> (F = fieldtype(T, n); F <: Tuple ? 1 : ndims(F)), Base._counttuple(T)))
 _maxndims(::Type{<:Tuple{T}}) where {T} = T <: Tuple ? 1 : ndims(T)
 function _maxndims(::Type{<:Tuple{T, S}}) where {T, S}
diff --git a/test/broadcast.jl b/test/broadcast.jl
index 57441de67c0ce..0f5bdf7a40bb1 100644
--- a/test/broadcast.jl
+++ b/test/broadcast.jl
@@ -930,6 +930,8 @@ let
 
     @test @inferred(Base.IteratorSize(Broadcast.broadcasted(+, (1,2,3), a1, zeros(3,3,3)))) === Base.HasShape{3}()
 
+    @test @inferred(Base.IteratorSize(Base.broadcasted(randn))) === Base.HasShape{0}()
+
     # inference on nested
     bc = Base.broadcasted(+, AD1(randn(3)), AD1(randn(3)))
     bc_nest = Base.broadcasted(+, bc , bc)