fix!: Replace LoadFunction::signature with LoadFunction::instantiation (#1756)

Closes #1755

This change breaks serialisation. We will already break serialisation
with the next release, so we judge this to be acceptable.

BREAKING CHANGE: The `LoadFunction::signature` field is removed. Replace
uses with `DataflowOpTrait::signature()`.

Author: doug-q

hugr-core/src/extension/resolution/types.rs

@@ -58,7 +58,7 @@ pub(crate) fn collect_op_types_extensions(
         OpType::LoadConstant(lc) => collect_type_exts(&lc.datatype, &mut used, &mut missing),
         OpType::LoadFunction(lf) => {
             collect_signature_exts(lf.func_sig.body(), &mut used, &mut missing);
-            collect_signature_exts(&lf.signature, &mut used, &mut missing);
+            collect_signature_exts(&lf.instantiation, &mut used, &mut missing);
         }
         OpType::DFG(dfg) => collect_signature_exts(&dfg.signature, &mut used, &mut missing),
         OpType::OpaqueOp(op) => {

hugr-core/src/extension/resolution/types_mut.rs

@@ -69,7 +69,7 @@ pub fn resolve_op_types_extensions(
         }
         OpType::LoadFunction(lf) => {
             resolve_signature_exts(node, lf.func_sig.body_mut(), extensions, used_extensions)?;
-            resolve_signature_exts(node, &mut lf.signature, extensions, used_extensions)?;
+            resolve_signature_exts(node, &mut lf.instantiation, extensions, used_extensions)?;
         }
         OpType::DFG(dfg) => {
             resolve_signature_exts(node, &mut dfg.signature, extensions, used_extensions)?

hugr-core/src/ops/dataflow.rs

@@ -7,10 +7,10 @@ use super::{impl_op_name, OpTag, OpTrait};
 use crate::extension::{ExtensionRegistry, ExtensionSet, SignatureError};
 use crate::ops::StaticTag;
 use crate::types::{EdgeKind, PolyFuncType, Signature, Type, TypeArg, TypeRow};
-use crate::IncomingPort;
+use crate::{type_row, IncomingPort};
 
 #[cfg(test)]
-use ::proptest_derive::Arbitrary;
+use proptest_derive::Arbitrary;
 
 /// Trait implemented by all dataflow operations.
 pub trait DataflowOpTrait {
@@ -347,7 +347,7 @@ pub struct LoadFunction {
     /// The type arguments that instantiate `func_sig`.
     pub type_args: Vec<TypeArg>,
     /// The instantiation of `func_sig`.
-    pub signature: Signature, // Cache, so we can fail in try_new() not in signature()
+    pub instantiation: Signature, // Cache, so we can fail in try_new() not in signature()
 }
 impl_op_name!(LoadFunction);
 impl DataflowOpTrait for LoadFunction {
@@ -358,7 +358,10 @@ impl DataflowOpTrait for LoadFunction {
     }
 
     fn signature(&self) -> Cow<'_, Signature> {
-        Cow::Borrowed(&self.signature)
+        Cow::Owned(Signature::new(
+            type_row![],
+            Type::new_function(self.instantiation.clone()),
+        ))
     }
 
     fn static_input(&self) -> Option<EdgeKind> {
@@ -377,11 +380,10 @@ impl LoadFunction {
     ) -> Result<Self, SignatureError> {
         let type_args: Vec<_> = type_args.into();
         let instantiation = func_sig.instantiate(&type_args, exts)?;
-        let signature = Signature::new(TypeRow::new(), vec![Type::new_function(instantiation)]);
         Ok(Self {
             func_sig,
             type_args,
-            signature,
+            instantiation,
         })
     }
 
@@ -410,12 +412,12 @@ impl LoadFunction {
             self.type_args.clone(),
             extension_registry,
         )?;
-        if other.signature == self.signature {
+        if other.instantiation == self.instantiation {
             Ok(())
         } else {
             Err(SignatureError::LoadFunctionIncorrectlyAppliesType {
-                cached: self.signature.clone(),
-                expected: other.signature.clone(),
+                cached: self.instantiation.clone(),
+                expected: other.instantiation.clone(),
             })
         }
     }

hugr-py/src/hugr/_serialization/ops.py

@@ -367,18 +367,12 @@ class LoadFunction(DataflowOp):
     op: Literal["LoadFunction"] = "LoadFunction"
     func_sig: PolyFuncType
     type_args: list[stys.TypeArg]
-    signature: FunctionType
+    instantiation: FunctionType
 
     def deserialize(self) -> ops.LoadFunc:
-        signature = self.signature.deserialize()
-        assert len(signature.input) == 0
-        (f_ty,) = signature.output
-        assert isinstance(
-            f_ty, tys.FunctionType
-        ), "Expected single function type output"
         return ops.LoadFunc(
             self.func_sig.deserialize(),
-            f_ty,
+            self.instantiation.deserialize(),
             deser_it(self.type_args),
         )
 

hugr-py/src/hugr/ops.py

@@ -1237,7 +1237,7 @@ def _to_serial(self, parent: Node) -> sops.LoadFunction:
             parent=parent.idx,
             func_sig=self.signature._to_serial(),
             type_args=ser_it(self.type_args),
-            signature=self.outer_signature()._to_serial(),
+            instantiation=self.instantiation._to_serial(),
         )
 
     def outer_signature(self) -> tys.FunctionType:

specification/schema/hugr_schema_live.json

@@ -1054,15 +1054,15 @@
                     "title": "Type Args",
                     "type": "array"
                 },
-                "signature": {
+                "instantiation": {
                     "$ref": "#/$defs/FunctionType"
                 }
             },
             "required": [
                 "parent",
                 "func_sig",
                 "type_args",
-                "signature"
+                "instantiation"
             ],
             "title": "LoadFunction",
             "type": "object"

specification/schema/hugr_schema_strict_live.json

@@ -1054,15 +1054,15 @@
                     "title": "Type Args",
                     "type": "array"
                 },
-                "signature": {
+                "instantiation": {
                     "$ref": "#/$defs/FunctionType"
                 }
             },
             "required": [
                 "parent",
                 "func_sig",
                 "type_args",
-                "signature"
+                "instantiation"
             ],
             "title": "LoadFunction",
             "type": "object"

specification/schema/testing_hugr_schema_live.json

@@ -1054,15 +1054,15 @@
                     "title": "Type Args",
                     "type": "array"
                 },
-                "signature": {
+                "instantiation": {
                     "$ref": "#/$defs/FunctionType"
                 }
             },
             "required": [
                 "parent",
                 "func_sig",
                 "type_args",
-                "signature"
+                "instantiation"
             ],
             "title": "LoadFunction",
             "type": "object"

specification/schema/testing_hugr_schema_strict_live.json

@@ -1054,15 +1054,15 @@
                     "title": "Type Args",
                     "type": "array"
                 },
-                "signature": {
+                "instantiation": {
                     "$ref": "#/$defs/FunctionType"
                 }
             },
             "required": [
                 "parent",
                 "func_sig",
                 "type_args",
-                "signature"
+                "instantiation"
             ],
             "title": "LoadFunction",
             "type": "object"