From d294b0eff07f80641dec4b8b478f9862d09ac297 Mon Sep 17 00:00:00 2001
From: Aayush Sabharwal <aayush.sabharwal@gmail.com>
Date: Mon, 20 Jan 2025 17:54:31 +0530
Subject: [PATCH] fix: handle unsized array symbolics in `linear_expansion`

---
 src/linear_algebra.jl | 1 +
 test/linear_solver.jl | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/src/linear_algebra.jl b/src/linear_algebra.jl
index bcaaaeaff..8f30fb095 100644
--- a/src/linear_algebra.jl
+++ b/src/linear_algebra.jl
@@ -328,6 +328,7 @@ function _linear_expansion(t, x)
     elseif op === getindex
         arrt, idxst... = arguments(t)
         isequal(arrt, arrx) && return (0, t, true)
+        shape(arrt) == Unknown() && return (0, t, true)
 
         indexed_t = OffsetArrays.Origin(map(first, axes(arrt)))(Symbolics.scalarize(arrt))[idxst...]
         # when indexing a registered function/callable symbolic
diff --git a/test/linear_solver.jl b/test/linear_solver.jl
index 8881f3b00..e3f038af8 100644
--- a/test/linear_solver.jl
+++ b/test/linear_solver.jl
@@ -77,4 +77,8 @@ a, b, islinear = Symbolics.linear_expansion(D(x) - x, x)
     @variables x[0:2]
     a, b, islin = Symbolics.linear_expansion(x[0] - z(x[1]), z(x[1]))
     @test islin && isequal(a, -1) && isequal(b, x[0])
+
+    @variables x::Vector{Real}
+    a, b, islin = Symbolics.linear_expansion(x[0] - z(x[1]), z(x[1]))
+    @test islin && isequal(a, -1) && isequal(b, x[0])
 end