feat!: ComposablePass trait allowing sequencing and validation

hugr-passes/src/composable.rs

@@ -0,0 +1,231 @@
+//! Compiler passes and utilities for composing them
+
+use std::{error::Error, marker::PhantomData};
+
+use hugr_core::hugr::{hugrmut::HugrMut, ValidationError};
+use hugr_core::HugrView;
+use itertools::Either;
+
+/// An optimization pass that can be sequenced with another and/or wrapped
+/// e.g. by [ValidatingPass]
+pub trait ComposablePass: Sized {
+    type Error: Error;
+    fn run(&self, hugr: &mut impl HugrMut) -> Result<(), Self::Error>;
+
+    fn map_err<E2: Error>(self, f: impl Fn(Self::Error) -> E2) -> impl ComposablePass<Error = E2> {
+        ErrMapper::new(self, f)
+    }
+
+    /// Returns a [ComposablePass] that does "`self` then `other`", so long as
+    /// `other::Err` maps into ours.
+    fn then<P: ComposablePass>(self, other: P) -> impl ComposablePass<Error = Self::Error>
+    where
+        P::Error: Into<Self::Error>,
+    {
+        (self, other.map_err(Into::into))
+    }
+
+    /// Returns a [ComposablePass] that does "`self` then `other`", combining
+    /// the two error types via `Either`
+    fn then_either<P: ComposablePass>(
+        self,
+        other: P,
+    ) -> impl ComposablePass<Error = Either<Self::Error, P::Error>> {
+        (self.map_err(Either::Left), other.map_err(Either::Right))
+    }
+
+    // Note: in the short term another variant could be useful:
+    // fn then_inf(self, other: impl ComposablePass<Err=Infallible>) -> impl ComposablePass<Err = Self::Err>
+    // however this will become redundant when Infallible is replaced by ! (never_type)
+    // as (unlike Infallible) ! converts Into anything
+}
+
+struct ErrMapper<P, E, F>(P, F, PhantomData<E>);
+
+impl<P: ComposablePass, E: Error, F: Fn(P::Error) -> E> ErrMapper<P, E, F> {
+    fn new(pass: P, err_fn: F) -> Self {
+        Self(pass, err_fn, PhantomData)
+    }
+}
+
+impl<P: ComposablePass, E: Error, F: Fn(P::Error) -> E> ComposablePass for ErrMapper<P, E, F> {
+    type Error = E;
+
+    fn run(&self, hugr: &mut impl HugrMut) -> Result<(), Self::Error> {
+        self.0.run(hugr).map_err(&self.1)
+    }
+}
+
+impl<E: Error, P1: ComposablePass<Error = E>, P2: ComposablePass<Error = E>> ComposablePass
+    for (P1, P2)
+{
+    type Error = E;
+
+    fn run(&self, hugr: &mut impl HugrMut) -> Result<(), Self::Error> {
+        self.0.run(hugr)?;
+        self.1.run(hugr)
+    }
+}
+
+/// Error from a [ValidatingPass]
+#[derive(thiserror::Error, Debug)]
+pub enum ValidatePassError<E> {
+    #[error("Failed to validate input HUGR: {err}\n{pretty_hugr}")]
+    Input {
+        #[source]
+        err: ValidationError,
+        pretty_hugr: String,
+    },
+    #[error("Failed to validate output HUGR: {err}\n{pretty_hugr}")]
+    Output {
+        #[source]
+        err: ValidationError,
+        pretty_hugr: String,
+    },
+    #[error(transparent)]
+    Underlying(#[from] E),
+}
+
+/// Runs an underlying pass, but with validation of the Hugr
+/// both before and afterwards.
+pub struct ValidatingPass<P>(P, bool);
+
+impl<P: ComposablePass> ValidatingPass<P> {
+    pub fn new_default(underlying: P) -> Self {
+        // Self(underlying, cfg!(feature = "extension_inference"))
+        // Sadly, many tests fail with extension inference, hence:
+        Self(underlying, false)
+    }
+
+    pub fn new_validating_extensions(underlying: P) -> Self {
+        Self(underlying, true)
+    }
+
+    pub fn new(underlying: P, validate_extensions: bool) -> Self {
+        Self(underlying, validate_extensions)
+    }
+
+    fn validation_impl<E>(
+        &self,
+        hugr: &impl HugrView,
+        mk_err: impl FnOnce(ValidationError, String) -> ValidatePassError<E>,
+    ) -> Result<(), ValidatePassError<E>> {
+        match self.1 {
+            false => hugr.validate_no_extensions(),
+            true => hugr.validate(),
+        }
+        .map_err(|err| mk_err(err, hugr.mermaid_string()))
+    }
+}
+
+impl<P: ComposablePass> ComposablePass for ValidatingPass<P> {
+    type Error = ValidatePassError<P::Error>;
+
+    fn run(&self, hugr: &mut impl HugrMut) -> Result<(), Self::Error> {
+        self.validation_impl(hugr, |err, pretty_hugr| ValidatePassError::Input {
+            err,
+            pretty_hugr,
+        })?;
+        self.0.run(hugr).map_err(ValidatePassError::Underlying)?;
+        self.validation_impl(hugr, |err, pretty_hugr| ValidatePassError::Output {
+            err,
+            pretty_hugr,
+        })
+    }
+}
+
+pub(crate) fn validate_if_test<P: ComposablePass>(
+    pass: P,
+    hugr: &mut impl HugrMut,
+) -> Result<(), ValidatePassError<P::Error>> {
+    if cfg!(test) {
+        ValidatingPass::new_default(pass).run(hugr)
+    } else {
+        pass.run(hugr).map_err(ValidatePassError::Underlying)
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use std::convert::Infallible;
+
+    use hugr_core::builder::{
+        Container, Dataflow, DataflowSubContainer, HugrBuilder, ModuleBuilder,
+    };
+    use hugr_core::extension::prelude::{bool_t, usize_t, ConstUsize};
+    use hugr_core::hugr::hugrmut::HugrMut;
+    use hugr_core::ops::{handle::NodeHandle, Input, Output, DEFAULT_OPTYPE, DFG};
+    use hugr_core::{types::Signature, Hugr, HugrView, IncomingPort};
+    use itertools::Either;
+
+    use crate::composable::{ValidatePassError, ValidatingPass};
+    use crate::const_fold::{ConstFoldError, ConstantFoldPass};
+    use crate::DeadCodeElimPass;
+
+    use super::ComposablePass;
+
+    #[test]
+    fn test_sequence() {
+        let mut mb = ModuleBuilder::new();
+        let id1 = mb
+            .define_function("id1", Signature::new_endo(usize_t()))
+            .unwrap();
+        let inps = id1.input_wires();
+        let id1 = id1.finish_with_outputs(inps).unwrap();
+        let id2 = mb
+            .define_function("id2", Signature::new_endo(usize_t()))
+            .unwrap();
+        let inps = id2.input_wires();
+        let id2 = id2.finish_with_outputs(inps).unwrap();
+        let hugr = mb.finish_hugr().unwrap();
+
+        let dce = DeadCodeElimPass::default().with_entry_points([id1.node()]);
+        let cfold =
+            ConstantFoldPass::default().with_inputs(id2.node(), [(0, ConstUsize::new(2).into())]);
+
+        cfold.run(&mut hugr.clone()).unwrap();
+
+        let exp_err = ConstFoldError::InvalidEntryPoint(id2.node(), DEFAULT_OPTYPE);
+        let r: Result<(), Either<Infallible, ConstFoldError>> = dce
+            .clone()
+            .then_either(cfold.clone())
+            .run(&mut hugr.clone());
+        assert_eq!(r, Err(Either::Right(exp_err.clone())));
+
+        let r: Result<(), ConstFoldError> = dce
+            .map_err(|inf| match inf {})
+            .then(cfold)
+            .run(&mut hugr.clone());
+        assert_eq!(r, Err(exp_err));
+    }
+
+    #[test]
+    fn test_validation() {
+        let mut h = Hugr::new(DFG {
+            signature: Signature::new(usize_t(), bool_t()),
+        });
+        let inp = h.add_node_with_parent(
+            h.root(),
+            Input {
+                types: usize_t().into(),
+            },
+        );
+        let outp = h.add_node_with_parent(
+            h.root(),
+            Output {
+                types: bool_t().into(),
+            },
+        );
+        h.connect(inp, 0, outp, 0);
+        let backup = h.clone();
+        let err = backup.validate().unwrap_err();
+
+        let no_inputs: [(IncomingPort, _); 0] = [];
+        let cfold = ConstantFoldPass::default().with_inputs(backup.root(), no_inputs);
+        cfold.run(&mut h).unwrap();
+        assert_eq!(h, backup); // Did nothing
+
+        let r = ValidatingPass(cfold, false).run(&mut h);
+        assert!(matches!(r, Err(ValidatePassError::Input { err: e, .. }) if e == err));
+    }
+}

hugr-passes/src/const_fold.rs

@@ -20,31 +20,30 @@ use hugr_core::{
 };
 use value_handle::ValueHandle;
 
-use crate::dataflow::{
-    partial_from_const, ConstLoader, ConstLocation, DFContext, Machine, PartialValue,
-    TailLoopTermination,
-};
 use crate::dead_code::{DeadCodeElimPass, PreserveNode};
-use crate::validation::{ValidatePassError, ValidationLevel};
+use crate::ComposablePass;
+use crate::{
+    composable::validate_if_test,
+    dataflow::{
+        partial_from_const, ConstLoader, ConstLocation, DFContext, Machine, PartialValue,
+        TailLoopTermination,
+    },
+};
 
 #[derive(Debug, Clone, Default)]
 /// A configuration for the Constant Folding pass.
 pub struct ConstantFoldPass {
-    validation: ValidationLevel,
     allow_increase_termination: bool,
     /// Each outer key Node must be either:
     ///   - a FuncDefn child of the root, if the root is a module; or
     ///   - the root, if the root is not a Module
     inputs: HashMap<Node, HashMap<IncomingPort, Value>>,
 }
 
-#[derive(Debug, Error)]
+#[derive(Clone, Debug, Error, PartialEq)]
 #[non_exhaustive]
 /// Errors produced by [ConstantFoldPass].
 pub enum ConstFoldError {
-    #[error(transparent)]
-    #[allow(missing_docs)]
-    ValidationError(#[from] ValidatePassError),
     /// Error raised when a Node is specified as an entry-point but
     /// is neither a dataflow parent, nor a [CFG](OpType::CFG), nor
     /// a [Conditional](OpType::Conditional).
@@ -53,12 +52,6 @@ pub enum ConstFoldError {
 }
 
 impl ConstantFoldPass {
-    /// Sets the validation level used before and after the pass is run
-    pub fn validation_level(mut self, level: ValidationLevel) -> Self {
-        self.validation = level;
-        self
-    }
-
     /// Allows the pass to remove potentially-non-terminating [TailLoop]s and [CFG] if their
     /// result (if/when they do terminate) is either known or not needed.
     ///
@@ -90,9 +83,18 @@ impl ConstantFoldPass {
             .extend(inputs.into_iter().map(|(p, v)| (p.into(), v)));
         self
     }
+}
+
+impl ComposablePass for ConstantFoldPass {
+    type Error = ConstFoldError;
 
     /// Run the Constant Folding pass.
-    fn run_no_validate(&self, hugr: &mut impl HugrMut) -> Result<(), ConstFoldError> {
+    ///
+    /// # Errors
+    ///
+    /// [ConstFoldError::InvalidEntryPoint] if an entry-point added by [Self::with_inputs]
+    /// was of an invalid [OpType]
+    fn run(&self, hugr: &mut impl HugrMut) -> Result<(), ConstFoldError> {
         let fresh_node = Node::from(portgraph::NodeIndex::new(
             hugr.nodes().max().map_or(0, |n| n.index() + 1),
         ));
@@ -168,23 +170,10 @@ impl ConstantFoldPass {
                     }
                 })
             })
-            .run(hugr)?;
+            .run(hugr)
+            .map_err(|inf| match inf {})?; // TODO use into_ok when available
         Ok(())
     }
-
-    /// Run the pass using this configuration.
-    ///
-    /// # Errors
-    ///
-    /// [ConstFoldError::ValidationError] if the Hugr does not validate before/afnerwards
-    /// (if [Self::validation_level] is set, or in tests)
-    ///
-    /// [ConstFoldError::InvalidEntryPoint] if an entry-point added by [Self::with_inputs]
-    /// was of an invalid OpType
-    pub fn run<H: HugrMut>(&self, hugr: &mut H) -> Result<(), ConstFoldError> {
-        self.validation
-            .run_validated_pass(hugr, |hugr: &mut H, _| self.run_no_validate(hugr))
-    }
 }
 
 /// Exhaustively apply constant folding to a HUGR.
@@ -202,18 +191,11 @@ pub fn constant_fold_pass<H: HugrMut>(h: &mut H) {
     } else {
         c
     };
-    c.run(h).unwrap()
+    validate_if_test(c, h).unwrap()
 }
 
 struct ConstFoldContext<'a, H>(&'a H);
 
-impl<H: HugrView> std::ops::Deref for ConstFoldContext<'_, H> {
-    type Target = H;
-    fn deref(&self) -> &H {
-        self.0
-    }
-}
-
 impl<H: HugrView<Node = Node>> ConstLoader<ValueHandle<H::Node>> for ConstFoldContext<'_, H> {
     type Node = H::Node;
 
@@ -244,7 +226,7 @@ impl<H: HugrView<Node = Node>> ConstLoader<ValueHandle<H::Node>> for ConstFoldCo
         };
         // Returning the function body as a value, here, would be sufficient for inlining IndirectCall
         // but not for transforming to a direct Call.
-        let func = DescendantsGraph::<FuncID<true>>::try_new(&**self, node).ok()?;
+        let func = DescendantsGraph::<FuncID<true>>::try_new(self.0, node).ok()?;
         Some(ValueHandle::new_const_hugr(
             ConstLocation::Node(node),
             Box::new(func.extract_hugr()),

hugr-passes/src/const_fold/test.rs

@@ -32,6 +32,7 @@ use hugr_core::types::{Signature, SumType, Type, TypeBound, TypeRow, TypeRowRV};
 use hugr_core::{type_row, Hugr, HugrView, IncomingPort, Node};
 
 use crate::dataflow::{partial_from_const, DFContext, PartialValue};
+use crate::ComposablePass as _;
 
 use super::{constant_fold_pass, ConstFoldContext, ConstantFoldPass, ValueHandle};