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Diffstat (limited to 'dhall/src/core/value.rs')
| -rw-r--r-- | dhall/src/core/value.rs | 338 |
1 files changed, 0 insertions, 338 deletions
diff --git a/dhall/src/core/value.rs b/dhall/src/core/value.rs deleted file mode 100644 index bd7a9b9..0000000 --- a/dhall/src/core/value.rs +++ /dev/null @@ -1,338 +0,0 @@ -use std::cell::{Ref, RefCell, RefMut}; -use std::rc::Rc; - -use crate::syntax::{Builtin, Const, Span}; - -use crate::core::context::TypecheckContext; -use crate::core::valuef::ValueF; -use crate::core::var::{AlphaVar, Shift, Subst}; -use crate::error::{TypeError, TypeMessage}; -use crate::phase::normalize::{apply_any, normalize_whnf}; -use crate::phase::typecheck::{builtin_to_value, const_to_value}; -use crate::phase::{NormalizedExpr, Typed}; - -#[derive(Debug, Clone, Copy)] -pub(crate) enum Form { - /// No constraints; expression may not be normalized at all. - Unevaled, - /// Weak Head Normal Form, i.e. normalized up to the first constructor, but subexpressions may - /// not be normalized. This means that the first constructor of the contained ValueF is the first - /// constructor of the final Normal Form (NF). - WHNF, - /// Normal Form, i.e. completely normalized. - /// When all the Values in a ValueF are at least in WHNF, and recursively so, then the - /// ValueF is in NF. This is because WHNF ensures that we have the first constructor of the NF; so - /// if we have the first constructor of the NF at all levels, we actually have the NF. - NF, -} -use Form::{Unevaled, NF, WHNF}; - -/// Partially normalized value. -/// Invariant: if `form` is `WHNF`, `value` must be in Weak Head Normal Form -/// Invariant: if `form` is `NF`, `value` must be fully normalized -#[derive(Debug)] -struct ValueInternal { - form: Form, - value: ValueF, - /// This is None if and only if `value` is `Sort` (which doesn't have a type) - ty: Option<Value>, - span: Span, -} - -/// Stores a possibly unevaluated value. Gets (partially) normalized on-demand, -/// sharing computation automatically. Uses a RefCell to share computation. -/// Can optionally store a type from typechecking to preserve type information. -#[derive(Clone)] -pub(crate) struct Value(Rc<RefCell<ValueInternal>>); - -#[derive(Copy, Clone)] -/// Controls conversion from `Value` to `Expr` -pub(crate) struct ToExprOptions { - /// Whether to convert all variables to `_` - pub(crate) alpha: bool, - /// Whether to normalize before converting - pub(crate) normalize: bool, -} - -impl ValueInternal { - fn into_value(self) -> Value { - Value(Rc::new(RefCell::new(self))) - } - fn as_valuef(&self) -> &ValueF { - &self.value - } - - fn normalize_whnf(&mut self) { - take_mut::take_or_recover( - self, - // Dummy value in case the other closure panics - || ValueInternal { - form: Unevaled, - value: ValueF::Const(Const::Type), - ty: None, - span: Span::Artificial, - }, - |vint| match (&vint.form, &vint.ty) { - (Unevaled, Some(ty)) => ValueInternal { - form: WHNF, - value: normalize_whnf(vint.value, &ty), - ty: vint.ty, - span: vint.span, - }, - // `value` is `Sort` - (Unevaled, None) => ValueInternal { - form: NF, - value: ValueF::Const(Const::Sort), - ty: None, - span: vint.span, - }, - // Already in WHNF - (WHNF, _) | (NF, _) => vint, - }, - ) - } - fn normalize_nf(&mut self) { - match self.form { - Unevaled => { - self.normalize_whnf(); - self.normalize_nf(); - } - WHNF => { - self.value.normalize_mut(); - self.form = NF; - } - // Already in NF - NF => {} - } - } - - fn get_type(&self) -> Result<&Value, TypeError> { - match &self.ty { - Some(t) => Ok(t), - None => { - Err(TypeError::new(&TypecheckContext::new(), TypeMessage::Sort)) - } - } - } -} - -impl Value { - fn new(value: ValueF, form: Form, ty: Value, span: Span) -> Value { - ValueInternal { - form, - value, - ty: Some(ty), - span, - } - .into_value() - } - pub(crate) fn const_sort() -> Value { - ValueInternal { - form: NF, - value: ValueF::Const(Const::Sort), - ty: None, - span: Span::Artificial, - } - .into_value() - } - pub(crate) fn from_valuef_and_type(v: ValueF, t: Value) -> Value { - Value::new(v, Unevaled, t, Span::Artificial) - } - pub(crate) fn from_valuef_and_type_and_span( - v: ValueF, - t: Value, - span: Span, - ) -> Value { - Value::new(v, Unevaled, t, span) - } - pub(crate) fn from_valuef_and_type_whnf(v: ValueF, t: Value) -> Value { - Value::new(v, WHNF, t, Span::Artificial) - } - pub(crate) fn from_const(c: Const) -> Self { - const_to_value(c) - } - pub(crate) fn from_builtin(b: Builtin) -> Self { - builtin_to_value(b) - } - pub(crate) fn with_span(self, span: Span) -> Self { - self.as_internal_mut().span = span; - self - } - - pub(crate) fn as_const(&self) -> Option<Const> { - match &*self.as_whnf() { - ValueF::Const(c) => Some(*c), - _ => None, - } - } - pub(crate) fn span(&self) -> Span { - self.as_internal().span.clone() - } - - fn as_internal(&self) -> Ref<ValueInternal> { - self.0.borrow() - } - fn as_internal_mut(&self) -> RefMut<ValueInternal> { - self.0.borrow_mut() - } - /// WARNING: The returned ValueF may be entirely unnormalized, in aprticular it may just be an - /// unevaled PartialExpr. You probably want to use `as_whnf`. - fn as_valuef(&self) -> Ref<ValueF> { - Ref::map(self.as_internal(), ValueInternal::as_valuef) - } - /// This is what you want if you want to pattern-match on the value. - /// WARNING: drop this ref before normalizing the same value or you will run into BorrowMut - /// panics. - pub(crate) fn as_whnf(&self) -> Ref<ValueF> { - self.normalize_whnf(); - self.as_valuef() - } - - pub(crate) fn to_expr(&self, opts: ToExprOptions) -> NormalizedExpr { - if opts.normalize { - self.normalize_whnf(); - } - self.as_valuef().to_expr(opts) - } - pub(crate) fn to_whnf_ignore_type(&self) -> ValueF { - self.as_whnf().clone() - } - /// Before discarding type information, check that it matches the expected return type. - pub(crate) fn to_whnf_check_type(&self, ty: &Value) -> ValueF { - self.check_type(ty); - self.to_whnf_ignore_type() - } - pub(crate) fn into_typed(self) -> Typed { - Typed::from_value(self) - } - - /// Mutates the contents. If no one else shares this, this avoids a RefCell lock. - fn mutate_internal(&mut self, f: impl FnOnce(&mut ValueInternal)) { - match Rc::get_mut(&mut self.0) { - // Mutate directly if sole owner - Some(refcell) => f(RefCell::get_mut(refcell)), - // Otherwise mutate through the refcell - None => f(&mut self.as_internal_mut()), - } - } - /// Normalizes contents to normal form; faster than `normalize_nf` if - /// no one else shares this. - pub(crate) fn normalize_mut(&mut self) { - self.mutate_internal(|vint| vint.normalize_nf()) - } - - pub(crate) fn normalize_whnf(&self) { - let borrow = self.as_internal(); - match borrow.form { - Unevaled => { - drop(borrow); - self.as_internal_mut().normalize_whnf(); - } - // Already at least in WHNF - WHNF | NF => {} - } - } - - pub(crate) fn app(&self, v: Value) -> Value { - let body_t = match &*self.get_type_not_sort().as_whnf() { - ValueF::Pi(x, t, e) => { - v.check_type(t); - e.subst_shift(&x.into(), &v) - } - _ => unreachable!("Internal type error"), - }; - Value::from_valuef_and_type_whnf( - apply_any(self.clone(), v, &body_t), - body_t, - ) - } - - /// In debug mode, panic if the provided type doesn't match the value's type. - /// Otherwise does nothing. - pub(crate) fn check_type(&self, ty: &Value) { - debug_assert_eq!( - Some(ty), - self.get_type().ok().as_ref(), - "Internal type error" - ); - } - pub(crate) fn get_type(&self) -> Result<Value, TypeError> { - Ok(self.as_internal().get_type()?.clone()) - } - /// When we know the value isn't `Sort`, this gets the type directly - pub(crate) fn get_type_not_sort(&self) -> Value { - self.get_type() - .expect("Internal type error: value is `Sort` but shouldn't be") - } -} - -impl Shift for Value { - fn shift(&self, delta: isize, var: &AlphaVar) -> Option<Self> { - Some(Value(self.0.shift(delta, var)?)) - } -} - -impl Shift for ValueInternal { - fn shift(&self, delta: isize, var: &AlphaVar) -> Option<Self> { - Some(ValueInternal { - form: self.form, - value: self.value.shift(delta, var)?, - ty: self.ty.shift(delta, var)?, - span: self.span.clone(), - }) - } -} - -impl Subst<Value> for Value { - fn subst_shift(&self, var: &AlphaVar, val: &Value) -> Self { - match &*self.as_valuef() { - // If the var matches, we can just reuse the provided value instead of copying it. - // We also check that the types match, if in debug mode. - ValueF::Var(v) if v == var => { - if let Ok(self_ty) = self.get_type() { - val.check_type(&self_ty.subst_shift(var, val)); - } - val.clone() - } - _ => Value(self.0.subst_shift(var, val)), - } - } -} - -impl Subst<Value> for ValueInternal { - fn subst_shift(&self, var: &AlphaVar, val: &Value) -> Self { - ValueInternal { - // The resulting value may not stay in wnhf after substitution - form: Unevaled, - value: self.value.subst_shift(var, val), - ty: self.ty.subst_shift(var, val), - span: self.span.clone(), - } - } -} - -// TODO: use Rc comparison to shortcut on identical pointers -impl std::cmp::PartialEq for Value { - fn eq(&self, other: &Self) -> bool { - *self.as_whnf() == *other.as_whnf() - } -} -impl std::cmp::Eq for Value {} - -impl std::fmt::Debug for Value { - fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { - let vint: &ValueInternal = &self.as_internal(); - if let ValueF::Const(c) = &vint.value { - write!(fmt, "{:?}", c) - } else { - let mut x = fmt.debug_struct(&format!("Value@{:?}", &vint.form)); - x.field("value", &vint.value); - if let Some(ty) = vint.ty.as_ref() { - x.field("type", &ty); - } else { - x.field("type", &None::<()>); - } - x.finish() - } - } -} |