From 88740928a3cef626feacf0417366323ae3026890 Mon Sep 17 00:00:00 2001
From: odow <o.dowson@gmail.com>
Date: Mon, 30 Oct 2023 13:08:01 +1300
Subject: [PATCH] Fix docs

---
 docs/src/manual/variables.md | 19 -------------------
 src/aff_expr.jl              |  6 ++++--
 2 files changed, 4 insertions(+), 21 deletions(-)

diff --git a/docs/src/manual/variables.md b/docs/src/manual/variables.md
index aa69b829841..ce8d6cf11a5 100644
--- a/docs/src/manual/variables.md
+++ b/docs/src/manual/variables.md
@@ -1214,25 +1214,6 @@ julia> @variable(model, x[1:2, 1:2] in SkewSymmetricMatrixSpace())
     `model`; the remaining elements in `x` are linear transformations of the
     single variable.
 
-Because the returned matrix `x` is `Matrix{AffExpr}`, you cannot use
-variable-related functions on its elements:
-```jldoctest skewsymmetric
-julia> set_lower_bound(x[1, 2], 0.0)
-ERROR: MethodError: no method matching set_lower_bound(::AffExpr, ::Float64)
-[...]
-```
-
-Instead, you can convert an upper-triangular elements to a variable as follows:
-```jldoctest skewsymmetric
-julia> to_variable(x::AffExpr) = first(keys(x.terms))
-to_variable (generic function with 1 method)
-
-julia> to_variable(x[1, 2])
-x[1,2]
-
-julia> set_lower_bound(to_variable(x[1, 2]), 0.0)
-```
-
 ### Example: Hermitian positive semidefinite variables
 
 Declare a matrix of JuMP variables to be Hermitian positive semidefinite using
diff --git a/src/aff_expr.jl b/src/aff_expr.jl
index cfb54aaef51..faa7a5c0f15 100644
--- a/src/aff_expr.jl
+++ b/src/aff_expr.jl
@@ -824,13 +824,15 @@ function _eval_as_variable(f::F, x::GenericAffExpr, args...) where {F}
             "Cannot call $f with $x because it is not a real-valued affine " *
             "expression of one variable.",
         )
-    elseif !isone(first(values(x.terms)))
+    end
+    variable, coefficient = first(x.terms)
+    if !isone(coefficient)
         error(
             "Cannot call $f with $x because it is not a real-valued affine " *
             "expression of one variable with a coefficient of `+1`.",
         )
     end
-    return f(first(keys(x.terms)), args...)
+    return f(variable, args...)
 end
 
 function _eval_as_variable(