Improves error messages for mismatched terms.

Serendipitously, this can also use the new `wadler_lindig` library for pretty-printing complicated types.

.pre-commit-config.yaml

@@ -11,4 +11,4 @@ repos:
     rev: v1.1.350
     hooks:
     - id: pyright
-      additional_dependencies: [equinox, jax, jaxtyping, optax, optimistix, lineax, pytest, typeguard==2.13.3, typing_extensions]
+      additional_dependencies: [equinox, jax, jaxtyping, optax, optimistix, lineax, pytest, typeguard==2.13.3, typing_extensions, wadler_lindig]

diffrax/_custom_types.py

@@ -112,6 +112,14 @@ class SpaceTimeTimeLevyArea(AbstractSpaceTimeTimeLevyArea):
     K: BM
 
 
+AbstractBrownianIncrement.__module__ = "diffrax"
+AbstractSpaceTimeLevyArea.__module__ = "diffrax"
+AbstractSpaceTimeTimeLevyArea.__module__ = "diffrax"
+BrownianIncrement.__module__ = "diffrax"
+SpaceTimeLevyArea.__module__ = "diffrax"
+SpaceTimeTimeLevyArea.__module__ = "diffrax"
+
+
 def levy_tree_transpose(
     tree_shape, tree: PyTree[AbstractBrownianIncrement]
 ) -> AbstractBrownianIncrement:

diffrax/_integrate.py

@@ -22,6 +22,7 @@
 import lineax.internal as lxi
 import numpy as np
 import optimistix as optx
+import wadler_lindig as wl
 from jaxtyping import Array, ArrayLike, Float, Inexact, PyTree, Real
 
 from ._adjoint import AbstractAdjoint, RecursiveCheckpointAdjoint
@@ -184,7 +185,11 @@ def _check(term_cls, term, term_contr_kwargs, yi):
                     better_isinstance, control_type, control_type_expected
                 )
                 if not control_type_compatible:
-                    raise ValueError(f"Control term {term} is incompatible.")
+                    raise ValueError(
+                        "Control term is incompatible: the returned control (e.g. "
+                        f"Brownian motion for an SDE) was {control_type}, but this "
+                        f"solver expected {control_type_expected}."
+                    )
             else:
                 assert False, "Malformed term structure"
             # If we've got to this point then the term is compatible
@@ -194,7 +199,13 @@ def _check(term_cls, term, term_contr_kwargs, yi):
             jtu.tree_map(_check, term_structure, terms, contr_kwargs, y)
     except Exception as e:
         # ValueError may also arise from mismatched tree structures
-        raise ValueError("Terms are not compatible with solver!") from e
+        pretty_term = wl.pformat(terms)
+        pretty_expected = wl.pformat(term_structure)
+        raise ValueError(
+            f"Terms are not compatible with solver! Got:\n{pretty_term}\nbut expected:"
+            f"\n{pretty_expected}\nNote that terms are checked recursively: if you "
+            "scroll up you may find a root-cause error that is more specific."
+        ) from e
 
 
 def _is_subsaveat(x: Any) -> bool:

diffrax/_term.py

@@ -981,3 +981,12 @@ def prod(
         self, vf: UnderdampedLangevinTuple, control: RealScalarLike
     ) -> UnderdampedLangevinTuple:
         return jtu.tree_map(lambda _vf: control * _vf, vf)
+
+
+AbstractTerm.__module__ = "diffrax"
+ODETerm.__module__ = "diffrax"
+ControlTerm.__module__ = "diffrax"
+WeaklyDiagonalControlTerm.__module__ = "diffrax"
+MultiTerm.__module__ = "diffrax"
+UnderdampedLangevinDriftTerm.__module__ = "diffrax"
+UnderdampedLangevinDiffusionTerm.__module__ = "diffrax"

pyproject.toml

@@ -23,7 +23,7 @@ classifiers = [
     "Topic :: Scientific/Engineering :: Mathematics",
 ]
 urls = {repository = "https://github.com/patrick-kidger/diffrax" }
-dependencies = ["jax>=0.4.38", "jaxtyping>=0.2.24", "typing_extensions>=4.5.0", "typeguard==2.13.3", "equinox>=0.11.10", "lineax>=0.0.5", "optimistix>=0.0.10"]
+dependencies = ["jax>=0.4.38", "jaxtyping>=0.2.24", "typing_extensions>=4.5.0", "typeguard==2.13.3", "equinox>=0.11.10", "lineax>=0.0.5", "optimistix>=0.0.10", "wadler_lindig>=0.1.1"]
 
 [build-system]
 requires = ["hatchling"]