From 1f5d851cb77fd9f794b34596a0ccad7de56e185e Mon Sep 17 00:00:00 2001
From: mtfishman <mfishman@flatironinstitute.org>
Date: Wed, 25 Jun 2025 12:41:31 -0400
Subject: [PATCH 1/2] Preserve blocking of indices when slicing a unit range
 with a blocked unit range

---
 Project.toml              |  2 +-
 src/blockaxis.jl          | 20 ++++++++++++++++++++
 test/test_blockindices.jl | 34 ++++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/Project.toml b/Project.toml
index edf66627..e455ea42 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,6 +1,6 @@
 name = "BlockArrays"
 uuid = "8e7c35d0-a365-5155-bbbb-fb81a777f24e"
-version = "1.6.3"
+version = "1.6.4"
 
 [deps]
 ArrayLayouts = "4c555306-a7a7-4459-81d9-ec55ddd5c99a"
diff --git a/src/blockaxis.jl b/src/blockaxis.jl
index 57e14ce8..d8333202 100644
--- a/src/blockaxis.jl
+++ b/src/blockaxis.jl
@@ -105,6 +105,16 @@ function Base.AbstractUnitRange{T}(r::BlockedUnitRange) where {T}
     return _BlockedUnitRange(convert(T,first(r)), convert.(T,blocklasts(r)))
 end
 
+# See: https://github.com/JuliaLang/julia/blob/b06d26075bf7b3f4e7f1b64b120f5665d8ed76f9/base/range.jl#L991-L1004
+function Base.getindex(r::AbstractUnitRange, s::AbstractBlockedUnitRange{T}) where {T<:Integer}
+    @boundscheck checkbounds(r, s)
+
+    f = first(r)
+    start = oftype(f, f + first(s) - firstindex(r))
+    lens = map(Base.Fix1(oftype, f), blocklengths(s))
+    return blockedrange(start, lens)
+end
+
 """
     BlockedOneTo{T, <:Union{AbstractVector{T}, NTuple{<:Any,T}}} where {T}
 
@@ -164,6 +174,16 @@ function Base.AbstractUnitRange{T}(r::BlockedOneTo) where {T}
     return BlockedOneTo(convert.(T,blocklasts(r)))
 end
 
+# See: https://github.com/JuliaLang/julia/blob/b06d26075bf7b3f4e7f1b64b120f5665d8ed76f9/base/range.jl#L1006-L1010
+function getindex(r::Base.OneTo{T}, s::BlockedOneTo) where T
+    @inline
+    @boundscheck checkbounds(r, s)
+    return BlockedOneTo(T.(blocklasts(s)))
+end
+function getindex(r::BlockedOneTo{T}, s::BlockedOneTo) where T
+    return Base.OneTo(r)[s]
+end
+
 """
     blockedrange(blocklengths::Union{Tuple, AbstractVector})
     blockedrange(first::Integer, blocklengths::Union{Tuple, AbstractVector})
diff --git a/test/test_blockindices.jl b/test/test_blockindices.jl
index b57512be..975b655e 100644
--- a/test/test_blockindices.jl
+++ b/test/test_blockindices.jl
@@ -323,6 +323,40 @@ end
         end
     end
 
+    @testset "BlockedUnitRange indexing" begin
+        a = 2:10
+        b = blockedrange(2, [1,2,3])
+        @test a[b] == blockedrange(3, [1,2,3])
+        @test a[b] isa BlockedUnitRange
+        @test first(a[b]) == 3
+        @test blocklengths(a[b]) == [1,2,3]
+        @test_throws BoundsError a[blockedrange(5, [1,2,3])]
+
+        a = blockedrange(2, [4,5])
+        b = blockedrange(2, [1,2,3])
+        @test a[b] == blockedrange(3, [1,2,3])
+        @test a[b] isa BlockedUnitRange
+        @test first(a[b]) == 3
+        @test blocklengths(a[b]) == [1,2,3]
+        @test_throws BoundsError a[blockedrange(5, [1,2,3])]
+
+        a = Base.OneTo(9)
+        b = blockedrange([1,2,3])
+        @test a[b] == blockedrange([1,2,3])
+        @test a[b] isa BlockedOneTo
+        @test first(a[b]) == 1
+        @test blocklengths(a[b]) == [1,2,3]
+        @test_throws BoundsError a[blockedrange([1,2,3,4])]
+
+        a = blockedrange([4,5])
+        b = blockedrange([1,2,3])
+        @test a[b] == blockedrange([1,2,3])
+        @test a[b] isa BlockedOneTo
+        @test first(a[b]) == 1
+        @test blocklengths(a[b]) == [1,2,3]
+        @test_throws BoundsError a[blockedrange([1,2,3,4])]
+    end
+
     @testset "misc" begin
         b = blockedrange(1, [1,2,3])
         @test axes(b) == Base.unsafe_indices(b) == (b,)

From 8a33d14e9104ed845d4f70a621669d931c3a121c Mon Sep 17 00:00:00 2001
From: Matt Fishman <mtfishman@users.noreply.github.com>
Date: Tue, 1 Jul 2025 10:40:33 -0400
Subject: [PATCH 2/2] Apply suggestions from code review

Co-authored-by: Sheehan Olver <solver@mac.com>
---
 src/blockaxis.jl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/blockaxis.jl b/src/blockaxis.jl
index d8333202..3a3542f6 100644
--- a/src/blockaxis.jl
+++ b/src/blockaxis.jl
@@ -178,10 +178,10 @@ end
 function getindex(r::Base.OneTo{T}, s::BlockedOneTo) where T
     @inline
     @boundscheck checkbounds(r, s)
-    return BlockedOneTo(T.(blocklasts(s)))
+    return BlockedOneTo(convert(AbstractVector{T}, blocklasts(s)))
 end
 function getindex(r::BlockedOneTo{T}, s::BlockedOneTo) where T
-    return Base.OneTo(r)[s]
+    return Base.oneto(r)[s]
 end
 
 """