feat: Type of constants in `core` `Term`s. #2411

zrho · 2025-07-04T10:31:45Z

This PR adds a Term::Const variant, representing the type of constants for a given runtime type. This corresponds to the core.const type in hugr-model.

Closes #2304.

codecov · 2025-07-04T10:34:27Z

Codecov Report

❌ Patch coverage is 71.42857% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.66%. Comparing base (06bc080) to head (3b9d156).
⚠️ Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
hugr-core/src/types/type_param.rs	42.85%	4 Missing ⚠️
hugr-core/src/import.rs	60.00%	0 Missing and 2 partials ⚠️
hugr-core/src/types/serialize.rs	0.00%	2 Missing ⚠️
hugr-core/src/extension/resolution/types.rs	0.00%	1 Missing ⚠️
hugr-core/src/extension/resolution/types_mut.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2411   +/-   ##
=======================================
  Coverage   82.66%   82.66%           
=======================================
  Files         251      251           
  Lines       46599    46644   +45     
  Branches    42160    42190   +30     
=======================================
+ Hits        38521    38559   +38     
- Misses       6028     6034    +6     
- Partials     2050     2051    +1

Flag	Coverage Δ
python	`91.35% <100.00%> (+0.02%)`	⬆️
rust	`81.74% <50.00%> (-0.01%)`	⬇️

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acl-cqc

Generally fine, a couple of suggestions - naming?

And, it's a bit of a shocker to have only 35% coverage! Obviously one cannot get very far without any terms of type Term::Const(....) but I think at the least you could add some roundtrip serialization tests and things like that?

acl-cqc · 2025-07-09T09:08:27Z

hugr-core/src/types/type_param.rs

    #[display("{_0}")]
    Variable(TermVar),
+
+    /// The type of constants for a runtime type.


Suggested change

/// The type of constants for a runtime type.

/// The type of constants, i.e. terms that can be turned into runtime values of a given (runtime) type.

Noting your example of qubit, I think we definitely want to say something stronger here - these are not static representations of the runtime values; they can (effectively) be arbitrary recipes or factories, procedures for production of.

(I think it's ok to continue to call them ConstType given "constants" are the common usage so long as we doc that really this is a more general concept than a constant)

(For example, there would not necessarily even be a guarantee that two runtime values produced by the same recipe would be equal, would there? I mean, there is not necessarily a notion of equality...but if there was!)

acl-cqc · 2025-07-09T09:10:23Z

hugr-core/src/types/type_param.rs

    Variable(TermVar),
+
+    /// The type of constants for a runtime type.
+    Const(Box<Type>),


I reckon this should be called ConstType, paralleling BytesType or RuntimeType. (In hindsight, using a Param suffix, rather than ...Type, would have been more similar to the python!).

There may never be a Const constructor (i.e. in the family of TypeArgs, a term that is/produces a runtime value) - rather, there will likely be a number of different ones, but I think we can still try to be consistent wrt. naming.

acl-cqc · 2025-07-09T09:11:53Z

hugr-core/src/types/type_param.rs

        (Term::TupleType(_), Term::StaticType) => Ok(()),
        (Term::RuntimeType(_), Term::StaticType) => Ok(()),
+        (Term::Const(_), Term::StaticType) => Ok(()),



I guess we do not want to say that e.g. Term::BoundedNat is a const (e.g. of Runtime type usize) but rather wait for a different term that does that?

Indeed! A Term::BoundedNat is a compile time value. It can be used as a parameter to a custom term that describes how to produce a particular type of runtime integer from it.

acl-cqc · 2025-07-09T09:13:43Z

hugr-py/tests/test_tys.py

            "(Linear, Nat(3))",
        ),
        (ListParam(StringParam()), "[String]"),
+        (ConstParam(Qubit), "Const(Qubit)"),


I'm sure this is valid** but it's a bit misleading, we are never going to have a Term that produces a Qubit "constant" are we?

** this is why we said constants have to be Copyable in hugr-core; I still feel it is a shame not to be able to here

Glad that I randomly picked that example then! Constants are descriptions on how to produce runtime values, so we can certainly have constants that produce qubits. Loading such a constant would mean preparing a qubit in a particular state.

(declare-ctr quantum.const_zero (core.const quantum.qubit)) (declare-ctr quantum.const_one (core.const quantum.qubit)) (declare-ctr quantum.const_plus (core.const quantum.qubit)) (declare-ctr quantum.const_minus (core.const quantum.qubit))

Note that the constant is always copyable since it is only the blueprint. The result of loading the constant need not be copyable. This is one of the advantages that are afforded by this system of constants.

Ok, indeed good you picked that one :). Let's be more explicit in the doc-comments on declaration of ConstType (I've commented there too), then.

zrho · 2025-07-09T10:51:03Z

Yeah, will add some roundtrip tests. I am looking forward to the day when we have custom terms so that PRs like this will become trivial.

acl-cqc

Thanks @zrho, sorry for dropping the ball. Nice! :) Just see comments on the doc for ConstType.

acl-cqc · 2025-07-29T20:15:58Z

hugr-core/src/types/type_param.rs

    #[display("{_0}")]
    Variable(TermVar),
+
+    /// The type of constants for a runtime type.


Noting your example of qubit, I think we definitely want to say something stronger here - these are not static representations of the runtime values; they can (effectively) be arbitrary recipes or factories, procedures for production of.

(I think it's ok to continue to call them ConstType given "constants" are the common usage so long as we doc that really this is a more general concept than a constant)

(For example, there would not necessarily even be a guarantee that two runtime values produced by the same recipe would be equal, would there? I mean, there is not necessarily a notion of equality...but if there was!)

acl-cqc · 2025-07-29T20:19:53Z

hugr-core/src/types/type_param.rs

+
+    /// The type of constants for a runtime type.
+    ///
+    /// A constant is a compile time description of a runtime value. The runtime


So here - it does not describe a runtime value - maybe a population of them (e.g. floats produced according to a distribution, right?) but it's weak and/or presumptive to say that the constant describes an (individual) value coming from it.

(You also can't go backwards, from runtime value to constant, but that's a side-issue)

acl-cqc · 2025-07-29T20:21:09Z

hugr-core/src/types/type_param.rs

        Self::TupleType(Box::new(item_types.into()))
    }

+    /// Creates a new [`Term::ConstType`] from a runtime type.


nit: perhaps

Suggested change

/// Creates a new [`Term::ConstType`] from a runtime type.

/// Creates a new [`Term::ConstType`] for a runtime type.

acl-cqc · 2025-07-29T20:25:43Z

hugr-py/tests/test_hugr_build.py

+
+    mod.declare_function(
+        "const_type",
+        tys.PolyFuncType(


right - nice example - statically parametric over a recipe for qubits, at runtime just produces qubits. Just to be clear - this is not like the one in model__roundtrip_const.snap, where the function's output is the constant (recipe) not the runtime type produced by it.

acl-cqc · 2025-07-29T20:26:43Z

hugr-core/tests/snapshots/model__roundtrip_const.snap

+  public
+  example.const_as_param
+  (param ?0 (core.const arithmetic.float.types.float64))
+  (core.fn [] [?0]))


Just to be clear - not sure if you can have a comment here or in model-const.edn? - the function here returns the constant recipe, not any runtime float....right?

Good catch, this is a type error. It should return the float.

acl-cqc · 2025-07-29T20:27:32Z

hugr-py/tests/test_tys.py

            "(Linear, Nat(3))",
        ),
        (ListParam(StringParam()), "[String]"),
+        (ConstParam(Qubit), "Const(Qubit)"),


Ok, indeed good you picked that one :). Let's be more explicit in the doc-comments on declaration of ConstType (I've commented there too), then.

## 🤖 New release * `hugr-model`: 0.22.1 -> 0.23.0 (✓ API compatible changes) * `hugr-core`: 0.22.1 -> 0.23.0 (⚠ API breaking changes) * `hugr-llvm`: 0.22.1 -> 0.23.0 (✓ API compatible changes) * `hugr-passes`: 0.22.1 -> 0.23.0 (✓ API compatible changes) * `hugr-persistent`: 0.2.1 -> 0.2.2 (✓ API compatible changes) * `hugr`: 0.22.1 -> 0.23.0 (✓ API compatible changes) * `hugr-cli`: 0.22.1 -> 0.23.0 (✓ API compatible changes) ### ⚠ `hugr-core` breaking changes ```text --- failure struct_missing: pub struct removed or renamed --- Description: A publicly-visible struct cannot be imported by its prior path. A `pub use` may have been removed, or the struct itself may have been renamed or removed entirely. ref: https://doc.rust-lang.org/cargo/reference/semver.html#item-remove impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.41.0/src/lints/struct_missing.ron Failed in: struct hugr_core::hugr::views::sibling_subgraph::TopoConvexChecker, previously in file /tmp/.tmpA42bjc/hugr-core/src/hugr/views/sibling_subgraph.rs:601 ``` <details><summary>Changelog</summary> ## `hugr-model` <blockquote> ## [0.23.0](hugr-model-v0.22.1...hugr-model-v0.23.0) - 2025-08-06 ### New Features - Type of constants in `core` `Term`s. ([#2411](#2411)) </blockquote> ## `hugr-core` <blockquote> ## [0.23.0](hugr-core-v0.22.1...hugr-core-v0.23.0) - 2025-08-06 ### New Features - Type of constants in `core` `Term`s. ([#2411](#2411)) - Support LineConvexChecker ([#2487](#2487)) </blockquote> ## `hugr-llvm` <blockquote> ## [0.23.0](hugr-llvm-v0.22.1...hugr-llvm-v0.23.0) - 2025-08-06 ### Bug Fixes - added public func getter for EmitFuncContext ([#2482](#2482)) - *(hugr-llvm)* Set llvm function linkage based on Visibility hugr node field ([#2502](#2502)) </blockquote> ## `hugr-passes` <blockquote> ## [0.22.1](hugr-passes-v0.22.0...hugr-passes-v0.22.1) - 2025-07-28 ### New Features - Include copy_discard_array in DelegatingLinearizer::default ([#2479](#2479)) - Inline calls to functions not on cycles in the call graph ([#2450](#2450)) </blockquote> ## `hugr-persistent` <blockquote> ## [0.2.0](hugr-persistent-v0.1.0...hugr-persistent-v0.2.0) - 2025-07-24 ### New Features - [**breaking**] Update portgraph dependency to 0.15 ([#2455](#2455)) </blockquote> ## `hugr` <blockquote> ## [0.23.0](hugr-v0.22.1...hugr-v0.23.0) - 2025-08-06 ### New Features - Type of constants in `core` `Term`s. ([#2411](#2411)) - Support LineConvexChecker ([#2487](#2487)) </blockquote> ## `hugr-cli` <blockquote> ## [0.23.0](hugr-cli-v0.22.1...hugr-cli-v0.23.0) - 2025-08-06 ### New Features - *(cli)* Deprecate HugrInputArgs::get_hugr ([#2506](#2506)) </blockquote> </details> --- This PR was generated with [release-plz](https://github.com/release-plz/release-plz/). --------- Co-authored-by: Luca Mondada <[email protected]>

🤖 I have created a release *beep* *boop* --- ## [0.13.1](hugr-py-v0.13.0...hugr-py-v0.13.1) (2025-08-18) ### Features * Add option to render a subgraph of a hugr. ([#2497](#2497)) ([c3370fe](c3370fe)) * **py:** implement `Sequence` protocol for qsys results/shots ([#2524](#2524)) ([b42e9df](b42e9df)) * Type of constants in `core` `Term`s. ([#2411](#2411)) ([2ba5764](2ba5764)) --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).

## 🤖 New release * `hugr-model`: 0.22.2 -> 0.22.3 (✓ API compatible changes) * `hugr-core`: 0.22.2 -> 0.22.3 (✓ API compatible changes) * `hugr-llvm`: 0.22.2 -> 0.22.3 (✓ API compatible changes) * `hugr-passes`: 0.22.2 -> 0.22.3 (✓ API compatible changes) * `hugr-persistent`: 0.2.2 -> 0.2.3 (✓ API compatible changes) * `hugr`: 0.22.2 -> 0.22.3 (✓ API compatible changes) * `hugr-cli`: 0.22.2 -> 0.22.3 (✓ API compatible changes) <details><summary>Changelog</summary> ## `hugr-model` <blockquote> ## [0.22.2](hugr-model-v0.22.1...hugr-model-v0.22.2) - 2025-08-06 ### New Features - Type of constants in `core` `Term`s. ([#2411](#2411)) </blockquote> ## `hugr-core` <blockquote> ## [0.22.3](hugr-core-v0.22.2...hugr-core-v0.22.3) - 2025-09-11 ### Bug Fixes - SiblingSubgraph::try_from_nodes not including disconnected components ([#2549](#2549)) ### Documentation - Clarify docs for SiblingSubgraph::{inputs, outputs} ([#2508](#2508)) ### New Features - SiblingSubgraph supports function calls ([#2528](#2528)) - Add unchecked constructor for SiblingSubgraph ([#2526](#2526)) - Add HugrMut::insert(_view)_forest ([#2518](#2518)) - Add extend_inputs function for DFGs ([#2536](#2536)) - Loosen bound on Patch trait ([#2545](#2545)) </blockquote> ## `hugr-llvm` <blockquote> ## [0.22.2](hugr-llvm-v0.22.1...hugr-llvm-v0.22.2) - 2025-08-06 ### Bug Fixes - added public func getter for EmitFuncContext ([#2482](#2482)) - *(hugr-llvm)* Set llvm function linkage based on Visibility hugr node field ([#2502](#2502)) </blockquote> ## `hugr-passes` <blockquote> ## [0.22.3](hugr-passes-v0.22.2...hugr-passes-v0.22.3) - 2025-09-11 ### New Features - SiblingSubgraph supports function calls ([#2528](#2528)) </blockquote> ## `hugr-persistent` <blockquote> ## [0.2.3](hugr-persistent-v0.2.2...hugr-persistent-v0.2.3) - 2025-09-11 ### Documentation - Clarify docs for SiblingSubgraph::{inputs, outputs} ([#2508](#2508)) ### New Features - SiblingSubgraph supports function calls ([#2528](#2528)) </blockquote> ## `hugr` <blockquote> ## [0.22.3](hugr-v0.22.2...hugr-v0.22.3) - 2025-09-11 ### Bug Fixes - SiblingSubgraph::try_from_nodes not including disconnected components ([#2549](#2549)) ### Documentation - Clarify docs for SiblingSubgraph::{inputs, outputs} ([#2508](#2508)) ### New Features - SiblingSubgraph supports function calls ([#2528](#2528)) - Add unchecked constructor for SiblingSubgraph ([#2526](#2526)) - Add extend_inputs function for DFGs ([#2536](#2536)) - Loosen bound on Patch trait ([#2545](#2545)) - Add HugrMut::insert(_view)_forest ([#2518](#2518)) </blockquote> ## `hugr-cli` <blockquote> ## [0.22.3](hugr-cli-v0.22.2...hugr-cli-v0.22.3) - 2025-09-11 ### New Features - *(hugr-cli)* CliError::validate helper ([#2507](#2507)) </blockquote> </details> --- This PR was generated with [release-plz](https://github.com/release-plz/release-plz/).

zrho changed the title ~~Type of constants in core Terms.~~ feat: Type of constants in core Terms. Jul 4, 2025

zrho force-pushed the push-kklpqyyxpskx branch 3 times, most recently from 3962e45 to 2c329cd Compare July 8, 2025 11:09

zrho requested a review from acl-cqc July 8, 2025 11:18

zrho marked this pull request as ready for review July 8, 2025 11:18

zrho requested a review from a team as a code owner July 8, 2025 11:18

zrho force-pushed the push-kklpqyyxpskx branch 3 times, most recently from 675c2ca to b9acbff Compare July 9, 2025 08:59

acl-cqc reviewed Jul 9, 2025

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zrho force-pushed the push-kklpqyyxpskx branch 2 times, most recently from 0585551 to 402cc24 Compare July 14, 2025 15:50

zrho self-assigned this Jul 16, 2025

zrho force-pushed the push-kklpqyyxpskx branch from 8965810 to 4af198b Compare July 28, 2025 10:56

zrho added 8 commits July 28, 2025 14:12

Type of constants in core Terms.

423a415

Add Const branch to new match in test.

75f7a9e

Rename Term::Const to Term::ConstType and add more docs.

d1c4699

Test import/export roundtrip of Term::ConstType.

2290eea

Update JSON schema to account for the Const to ConstType change.

448ece6

Lints.

69f4ba2

Add visibility modifier to test fixture.

385cf18

Add test for exporting const type parameter from python.

8b87571

zrho force-pushed the push-kklpqyyxpskx branch from 4af198b to 8b87571 Compare July 28, 2025 13:20

zrho requested a review from acl-cqc July 28, 2025 13:26

zrho mentioned this pull request Jul 29, 2025

Static functions as type arguments #2301

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acl-cqc approved these changes Jul 29, 2025

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Fixed test fixture.

3b9d156

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Merged via the queue into main with commit 2ba5764 Jul 30, 2025
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zrho deleted the push-kklpqyyxpskx branch July 30, 2025 10:25

This was referenced Jul 30, 2025

chore(main): release hugr-py 0.13.1 #2495

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chore: release #2493

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chore: release #2509

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hugrbot mentioned this pull request Sep 16, 2025

chore: release #2554

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	/// The type of constants for a runtime type.
	/// The type of constants, i.e. terms that can be turned into runtime values of a given (runtime) type.

	/// Creates a new [`Term::ConstType`] from a runtime type.
	/// Creates a new [`Term::ConstType`] for a runtime type.

feat: Type of constants in core Terms. #2411

feat: Type of constants in core Terms. #2411

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feat: Type of constants in `core` `Term`s. #2411

feat: Type of constants in `core` `Term`s. #2411

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