Relax AbstractOptimizer requirement in instantiate

src/Utilities/cachingoptimizer.jl

@@ -90,10 +90,7 @@ mutable struct CachingOptimizer{O,M<:MOI.ModelLike} <: MOI.AbstractOptimizer
         )
     end
 
-    function CachingOptimizer(
-        cache::MOI.ModelLike,
-        optimizer::MOI.AbstractOptimizer,
-    )
+    function CachingOptimizer(cache::MOI.ModelLike, optimizer::MOI.ModelLike)
         @assert MOI.is_empty(optimizer)
         model = new{typeof(optimizer),typeof(cache)}(
             optimizer,

src/instantiate.jl

@@ -55,18 +55,18 @@ const _INSTANTIATE_NOT_CALLABLE_MESSAGE =
     _instantiate_and_check(optimizer_constructor)
 
 Create an instance of optimizer by calling `optimizer_constructor`.
-Then check that the type returned is an empty [`AbstractOptimizer`](@ref).
+Then check that the type returned is an empty [`ModelLike`](@ref).
 """
 function _instantiate_and_check(optimizer_constructor)
     if !applicable(optimizer_constructor)
         error(_INSTANTIATE_NOT_CALLABLE_MESSAGE)
     end
     optimizer = optimizer_constructor()
-    if !isa(optimizer, AbstractOptimizer)
+    if !isa(optimizer, ModelLike)
         error(
             "The provided `optimizer_constructor` returned an object of type " *
             "$(typeof(optimizer)). Expected a " *
-            "MathOptInterface.AbstractOptimizer.",
+            "MathOptInterface.ModelLike.",
         )
     end
     if !is_empty(optimizer)

test/FileFormats/FileFormats.jl

@@ -49,6 +49,23 @@ function test_copying()
     end
 end
 
+function test_instantiate()
+    models = [
+        MOI.FileFormats.CBF.Model,
+        MOI.FileFormats.LP.Model,
+        MOI.FileFormats.MOF.Model,
+        MOI.FileFormats.MPS.Model,
+        MOI.FileFormats.SDPA.Model,
+    ]
+    for src in models
+        model = MOI.instantiate(src)
+        @test model isa src
+        bridged = MOI.instantiate(src; with_bridge_type = Float64)
+        @test bridged isa MOI.Bridges.LazyBridgeOptimizer
+    end
+    return
+end
+
 function test_compressed_open()
     for cs in [MOI.FileFormats.Bzip2(), MOI.FileFormats.Gzip()]
         for open_type in ["a", "r+", "w+", "a+"]

test/instantiate.jl

@@ -67,7 +67,7 @@ function _test_instantiate(T)
 
     err = ErrorException(
         "The provided `optimizer_constructor` returned an object of type " *
-        "$Int. Expected a MathOptInterface.AbstractOptimizer.",
+        "$Int. Expected a MathOptInterface.ModelLike.",
     )
     h() = 1
     @test_throws err MOI.instantiate(h)