From 630081f08d057940386c7519feb52898d9f89d0f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Beno=C3=AEt=20Legat?= <benoit.legat@gmail.com>
Date: Thu, 19 Mar 2026 14:22:20 +0100
Subject: [PATCH 1/3] Rethrow for bounds error when modifying constant vector

---
 src/Utilities/matrix_of_constraints.jl       | 14 +++++++--
 test/Utilities/test_matrix_of_constraints.jl | 32 +++++++++++++++++++-
 2 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/src/Utilities/matrix_of_constraints.jl b/src/Utilities/matrix_of_constraints.jl
index 503b149110..4aca58c866 100644
--- a/src/Utilities/matrix_of_constraints.jl
+++ b/src/Utilities/matrix_of_constraints.jl
@@ -709,8 +709,18 @@ function MOI.modify(
 )
     try
         modify_constants(model.constants, rows(model, ci), change.new_constant)
-    catch
-        throw(MOI.ModifyConstraintNotAllowed(ci, change))
+    catch err
+        if err isa MethodError
+            throw(
+                MOI.ModifyConstraintNotAllowed(
+                    ci,
+                    change,
+                    "`modify_constants` is not implemented for " *
+                    "`$(typeof(model.constants))`",
+                ),
+            )
+        end
+        rethrow(err)
     end
     return
 end
diff --git a/test/Utilities/test_matrix_of_constraints.jl b/test/Utilities/test_matrix_of_constraints.jl
index 256fb2a931..f545c2b3b9 100644
--- a/test/Utilities/test_matrix_of_constraints.jl
+++ b/test/Utilities/test_matrix_of_constraints.jl
@@ -763,6 +763,31 @@ function test_modify_vectorsets()
     return
 end
 
+function test_modify_constants_bounds_error()
+    model = _new_VectorSets()
+    src = MOI.Utilities.Model{Int}()
+    x = MOI.add_variables(src, 2)
+    c = MOI.add_constraint(
+        src,
+        MOI.VectorAffineFunction{Int}(
+            MOI.VectorAffineTerm.(1, MOI.ScalarAffineTerm.(1, x)),
+            [1, 3],
+        ),
+        MOI.SecondOrderCone(2),
+    )
+    index_map = MOI.copy_to(model, src)
+    resize!(model.constraints.constants, 0)
+    @test_throws(
+        BoundsError,
+        MOI.modify(
+            model.constraints,
+            index_map[c],
+            MOI.VectorConstantChange([4, 5]),
+        ),
+    )
+    return
+end
+
 function test_modify_set_constants()
     model = MOI.Utilities.Model{Float64}()
     x = MOI.add_variables(model, 3)
@@ -789,8 +814,13 @@ function test_modify_set_constants()
     index_map = MOI.copy_to(cache, model)
     ci = index_map[p_ref]
     change = MOI.VectorConstantChange([4.0, 5.0, 6.0])
+    constants_type = typeof(cache.constraints.constants)
     @test_throws(
-        MOI.ModifyConstraintNotAllowed(ci, change),
+        MOI.ModifyConstraintNotAllowed(
+            ci,
+            change,
+            "`modify_constants` is not implemented for `$constants_type`",
+        ),
         MOI.modify(cache, ci, change),
     )
     return

From 1c49e73f014be55498e994e35f9418dfc268faaf Mon Sep 17 00:00:00 2001
From: Oscar Dowson <o.dowson@gmail.com>
Date: Fri, 20 Mar 2026 14:22:03 +1300
Subject: [PATCH 2/3] Update

---
 src/Utilities/matrix_of_constraints.jl | 31 ++++++++++++++------------
 1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/src/Utilities/matrix_of_constraints.jl b/src/Utilities/matrix_of_constraints.jl
index 4aca58c866..9b4864274e 100644
--- a/src/Utilities/matrix_of_constraints.jl
+++ b/src/Utilities/matrix_of_constraints.jl
@@ -707,20 +707,14 @@ function MOI.modify(
     ci::MOI.ConstraintIndex,
     change::Union{MOI.ScalarConstantChange,MOI.VectorConstantChange},
 )
-    try
-        modify_constants(model.constants, rows(model, ci), change.new_constant)
-    catch err
-        if err isa MethodError
-            throw(
-                MOI.ModifyConstraintNotAllowed(
-                    ci,
-                    change,
-                    "`modify_constants` is not implemented for " *
-                    "`$(typeof(model.constants))`",
-                ),
-            )
-        end
-        rethrow(err)
+    ret = modify_constants(
+        model.constants,
+        rows(model, ci),
+        change.new_constant,
+    )
+    if ret == _ModifyConstantsNotImplemented()
+        msg = "`modify_constants` is not implemented for `$(typeof(model.constants))`"
+        throw(MOI.ModifyConstraintNotAllowed(ci, change, msg))
     end
     return
 end
@@ -748,6 +742,15 @@ function MOI.modify(
     return
 end
 
+# See https://github.com/jump-dev/MathOptInterface.jl/pull/2976
+# Ideally we would have made it so that `modify_constants` operated like
+# `modify_coefficients` and returned a `Bool` indicating success. But we didn't,
+# so here's a hacky work-around to catch if the method is not implemented
+# without resorting to a try-catch.
+struct _ModifyConstantsNotImplemented end
+
+modify_constants(args...) = _ModifyConstantsNotImplemented()
+
 function modify_constants(
     b::AbstractVector{T},
     row::Integer,

From b76bf57e320287969195294b97840f2fb9a044f9 Mon Sep 17 00:00:00 2001
From: Oscar Dowson <o.dowson@gmail.com>
Date: Fri, 20 Mar 2026 14:50:57 +1300
Subject: [PATCH 3/3] Fix format

---
 src/Utilities/matrix_of_constraints.jl | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/src/Utilities/matrix_of_constraints.jl b/src/Utilities/matrix_of_constraints.jl
index 9b4864274e..43d4f80448 100644
--- a/src/Utilities/matrix_of_constraints.jl
+++ b/src/Utilities/matrix_of_constraints.jl
@@ -707,11 +707,8 @@ function MOI.modify(
     ci::MOI.ConstraintIndex,
     change::Union{MOI.ScalarConstantChange,MOI.VectorConstantChange},
 )
-    ret = modify_constants(
-        model.constants,
-        rows(model, ci),
-        change.new_constant,
-    )
+    ret =
+        modify_constants(model.constants, rows(model, ci), change.new_constant)
     if ret == _ModifyConstantsNotImplemented()
         msg = "`modify_constants` is not implemented for `$(typeof(model.constants))`"
         throw(MOI.ModifyConstraintNotAllowed(ci, change, msg))