From c80efa2c2ab116108dd55ae861052971982189c2 Mon Sep 17 00:00:00 2001
From: odow <o.dowson@gmail.com>
Date: Mon, 30 Oct 2023 11:05:54 +1300
Subject: [PATCH 1/3] Add SkipModelConvertScalarSetWrapper

---
 docs/src/developers/extensions.md |  3 +++
 src/constraints.jl                | 39 +++++++++++++++++++++++++++----
 test/test_constraint.jl           |  9 +++++++
 3 files changed, 47 insertions(+), 4 deletions(-)

diff --git a/docs/src/developers/extensions.md b/docs/src/developers/extensions.md
index e2fbcd3fc26..9fe5f64be86 100644
--- a/docs/src/developers/extensions.md
+++ b/docs/src/developers/extensions.md
@@ -253,6 +253,9 @@ Rewriting my_equal_to to ==
     When parsing a constraint you can recurse into sub-constraint (for example, the
     `{expr}` in `z => {x <= 1}`) by calling [`parse_constraint`](@ref).
 
+To prevent JuMP from promoting the set to the same value type as the model, use
+[`SkipModelConvertScalarSetWrapper`](@ref).
+
 ### Build
 
 To extend the [`@constraint`](@ref) macro at build time, implement a new
diff --git a/src/constraints.jl b/src/constraints.jl
index dcb76d0d1c1..64c6e74655d 100644
--- a/src/constraints.jl
+++ b/src/constraints.jl
@@ -1543,16 +1543,47 @@ function relax_with_penalty!(
     return relax_with_penalty!(model, Dict(); default = default)
 end
 
-struct _DoNotConvertSet{S} <: MOI.AbstractScalarSet
+"""
+    SkipModelConvertScalarSetWrapper(set::MOI.AbstractScalarSet)
+
+JuMP uses [`model_convert`](@ref) to automatically promote [`MOI.AbstractScalarSet`](@ref)
+sets to the same [`value_type`](@ref) as the model.
+
+In cases there this is undesirable, wrap the set in `SkipModelConvertScalarSetWrapper`
+to pass the set un-changed to the solver.
+
+## Examples
+
+```jldoctest
+julia> model = Model();
+
+julia> @variable(model, x);
+
+julia> @constraint(model, x in MOI.EqualTo(1 // 2))
+x = 0.5
+
+julia> @constraint(model, x in SkipModelConvertScalarSetWrapper(MOI.EqualTo(1 // 2)))
+x = 1//2
+```
+"""
+struct SkipModelConvertScalarSetWrapper{S<:MOI.AbstractScalarSet} <:
+       MOI.AbstractScalarSet
     set::S
 end
 
-model_convert(::AbstractModel, set::_DoNotConvertSet) = set
+model_convert(::AbstractModel, set::SkipModelConvertScalarSetWrapper) = set
 
-moi_set(c::ScalarConstraint{F,<:_DoNotConvertSet}) where {F} = c.set.set
+function moi_set(
+    c::ScalarConstraint{F,<:SkipModelConvertScalarSetWrapper},
+) where {F}
+    return c.set.set
+end
 
 function _build_boolean_equal_to(::Function, lhs::AbstractJuMPScalar, rhs::Bool)
-    return ScalarConstraint(lhs, _DoNotConvertSet(MOI.EqualTo(rhs)))
+    return ScalarConstraint(
+        lhs,
+        SkipModelConvertScalarSetWrapper(MOI.EqualTo(rhs)),
+    )
 end
 
 function _build_boolean_equal_to(error_fn::Function, ::AbstractJuMPScalar, rhs)
diff --git a/test/test_constraint.jl b/test/test_constraint.jl
index de98fd8b331..318bc64de56 100644
--- a/test/test_constraint.jl
+++ b/test/test_constraint.jl
@@ -1763,4 +1763,13 @@ function test_def_equal_to_operator_bool()
     return
 end
 
+function test_SkipModelConvertScalarSetWrapper()
+    model = Model()
+    @variable(model, x)
+    set = MOI.EqualTo(1 // 2)
+    c1 = @constraint(model, x in set)
+    c2 = @constraint(model, x in SkipModelConvertScalarSetWrapper(set))
+    @test constraint_object(c1).set === MOI.EqualTo(0.5)
+    @test constraint_object(c2).set === MOI.EqualTo(1 // 2)
+    return
 end

From 106bccb7387a76d1681a6de36c344c5074be4706 Mon Sep 17 00:00:00 2001
From: Oscar Dowson <odow@users.noreply.github.com>
Date: Mon, 30 Oct 2023 11:57:50 +1300
Subject: [PATCH 2/3] Update test_constraint.jl

---
 test/test_constraint.jl | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/test/test_constraint.jl b/test/test_constraint.jl
index 318bc64de56..de30fc97c54 100644
--- a/test/test_constraint.jl
+++ b/test/test_constraint.jl
@@ -1773,3 +1773,6 @@ function test_SkipModelConvertScalarSetWrapper()
     @test constraint_object(c2).set === MOI.EqualTo(1 // 2)
     return
 end
+
+end  # module
+

From 60865dc111aee2f1356aa43bb343da9a58ad75d2 Mon Sep 17 00:00:00 2001
From: Oscar Dowson <odow@users.noreply.github.com>
Date: Mon, 30 Oct 2023 11:58:15 +1300
Subject: [PATCH 3/3] Update test_constraint.jl

---
 test/test_constraint.jl | 1 -
 1 file changed, 1 deletion(-)

diff --git a/test/test_constraint.jl b/test/test_constraint.jl
index de30fc97c54..59c734d4865 100644
--- a/test/test_constraint.jl
+++ b/test/test_constraint.jl
@@ -1775,4 +1775,3 @@ function test_SkipModelConvertScalarSetWrapper()
 end
 
 end  # module
-