Rewrite the StaticType trait and everything around it

8 files changed, 191 insertions, 241 deletions

diff --git a/dhall/src/api/mod.rs b/dhall/src/api/mod.rs
index 0a0ef93..72789d9 100644
--- a/dhall/src/api/mod.rs
+++ b/dhall/src/api/mod.rs
@@ -1,13 +1,88 @@
 mod serde;
+pub(crate) mod static_type;
 pub(crate) mod traits;
 
+// pub struct Value(crate::phase::Normalized);
+
+pub use typ::Type;
+
+mod typ {
+    use crate::core::thunk::{Thunk, TypeThunk};
+    use crate::core::value::Value;
+    use crate::phase::{NormalizedSubExpr, Typed};
+    use dhall_syntax::Builtin;
+
+    /// A Dhall expression representing a type.
+    ///
+    /// This captures what is usually simply called a "type", like
+    /// `Bool`, `{ x: Integer }` or `Natural -> Text`.
+    #[derive(Debug, Clone, PartialEq, Eq)]
+    pub struct Type(Typed);
+
+    impl Type {
+        pub(crate) fn from_value(v: Value) -> Self {
+            Type(Typed::from_value_untyped(v))
+        }
+        pub(crate) fn make_builtin_type(b: Builtin) -> Self {
+            Self::from_value(Value::from_builtin(b))
+        }
+        pub(crate) fn make_optional_type(t: Type) -> Self {
+            Self::from_value(Value::AppliedBuiltin(
+                Builtin::Optional,
+                vec![t.to_thunk()],
+            ))
+        }
+        pub(crate) fn make_list_type(t: Type) -> Self {
+            Self::from_value(Value::AppliedBuiltin(
+                Builtin::List,
+                vec![t.to_thunk()],
+            ))
+        }
+        #[doc(hidden)]
+        pub fn from_normalized_expr(e: NormalizedSubExpr) -> Self {
+            Type(Typed::from_normalized_expr_untyped(e))
+        }
+        #[doc(hidden)]
+        pub fn make_record_type(
+            kts: impl Iterator<Item = (String, Type)>,
+        ) -> Self {
+            Self::from_value(Value::RecordType(
+                kts.map(|(k, t)| {
+                    (k.into(), TypeThunk::from_thunk(t.to_thunk()))
+                })
+                .collect(),
+            ))
+        }
+        #[doc(hidden)]
+        pub fn make_union_type(
+            kts: impl Iterator<Item = (String, Option<Type>)>,
+        ) -> Self {
+            Self::from_value(Value::UnionType(
+                kts.map(|(k, t)| {
+                    (k.into(), t.map(|t| TypeThunk::from_thunk(t.to_thunk())))
+                })
+                .collect(),
+            ))
+        }
+
+        pub(crate) fn to_thunk(&self) -> Thunk {
+            self.0.to_thunk()
+        }
+        #[allow(dead_code)]
+        pub(crate) fn to_expr(&self) -> NormalizedSubExpr {
+            self.0.to_expr()
+        }
+    }
+}
+
 /// Deserialization of Dhall expressions into Rust
 pub mod de {
+    pub use super::static_type::StaticType;
+    pub use super::Type;
     #[doc(hidden)]
-    pub use crate::phase::SimpleType;
-    pub use crate::traits::{Deserialize, SimpleStaticType, StaticType};
+    pub use crate::traits::Deserialize;
     #[doc(hidden)]
-    pub use dhall_proc_macros::SimpleStaticType;
+    pub use dhall_proc_macros::StaticType;
 
     /// Deserialize an instance of type T from a string of Dhall text.
     ///
@@ -35,6 +110,8 @@ pub mod de {
     pub fn from_str_auto_type<'a, T: Deserialize<'a> + StaticType>(
         s: &'a str,
     ) -> crate::error::Result<T> {
-        from_str(s, Some(&<T as StaticType>::get_static_type()))
+        // from_str(s, Some(&<T as StaticType>::static_type()))
+        // TODO
+        from_str(s, None)
     }
 }
diff --git a/dhall/src/api/static_type.rs b/dhall/src/api/static_type.rs
new file mode 100644
index 0000000..906bcef
--- /dev/null
+++ b/dhall/src/api/static_type.rs
@@ -0,0 +1,93 @@
+use dhall_syntax::{Builtin, Integer, Natural};
+
+use crate::api::Type;
+
+/// A Rust type that can be represented as a Dhall type.
+///
+/// A typical example is `Option<bool>`,
+/// represented by the dhall expression `Optional Bool`.
+///
+/// This trait can and should be automatically derived.
+///
+/// The representation needs to be independent of the value.
+/// For this reason, something like `HashMap<String, bool>` cannot implement
+/// [StaticType] because each different value would
+/// have a different Dhall record type.
+pub trait StaticType {
+    fn static_type() -> Type;
+}
+
+macro_rules! derive_builtin {
+    ($ty:ty, $builtin:ident) => {
+        impl StaticType for $ty {
+            fn static_type() -> Type {
+                Type::make_builtin_type(Builtin::$builtin)
+            }
+        }
+    };
+}
+
+derive_builtin!(bool, Bool);
+derive_builtin!(Natural, Natural);
+derive_builtin!(u64, Natural);
+derive_builtin!(Integer, Integer);
+derive_builtin!(String, Text);
+
+impl<A, B> StaticType for (A, B)
+where
+    A: StaticType,
+    B: StaticType,
+{
+    fn static_type() -> Type {
+        Type::make_record_type(
+            vec![
+                ("_1".to_owned(), A::static_type()),
+                ("_2".to_owned(), B::static_type()),
+            ]
+            .into_iter(),
+        )
+    }
+}
+
+impl<T, E> StaticType for std::result::Result<T, E>
+where
+    T: StaticType,
+    E: StaticType,
+{
+    fn static_type() -> Type {
+        Type::make_union_type(
+            vec![
+                ("Ok".to_owned(), Some(T::static_type())),
+                ("Err".to_owned(), Some(E::static_type())),
+            ]
+            .into_iter(),
+        )
+    }
+}
+
+impl<T> StaticType for Option<T>
+where
+    T: StaticType,
+{
+    fn static_type() -> Type {
+        Type::make_optional_type(T::static_type())
+    }
+}
+
+impl<T> StaticType for Vec<T>
+where
+    T: StaticType,
+{
+    fn static_type() -> Type {
+        Type::make_list_type(T::static_type())
+    }
+}
+
+impl<'a, T> StaticType for &'a T
+where
+    T: StaticType,
+{
+    fn static_type() -> Type {
+        T::static_type()
+    }
+}
diff --git a/dhall/src/api/traits/dynamic_type.rs b/dhall/src/api/traits/dynamic_type.rs
deleted file mode 100644
index 7763a28..0000000
--- a/dhall/src/api/traits/dynamic_type.rs
+++ /dev/null
@@ -1,32 +0,0 @@
-use crate::error::TypeError;
-use crate::phase::{Normalized, Type, Typed};
-use crate::traits::StaticType;
-use std::borrow::Cow;
-
-pub trait DynamicType {
-    fn get_type<'a>(&'a self) -> Result<Cow<'a, Type>, TypeError>;
-}
-
-impl<T: StaticType> DynamicType for T {
-    fn get_type<'a>(&'a self) -> Result<Cow<'a, Type>, TypeError> {
-        Ok(Cow::Owned(T::get_static_type()))
-    }
-}
-
-impl DynamicType for Type {
-    fn get_type(&self) -> Result<Cow<'_, Type>, TypeError> {
-        self.get_type()
-    }
-}
-
-impl DynamicType for Normalized {
-    fn get_type(&self) -> Result<Cow<'_, Type>, TypeError> {
-        self.0.get_type()
-    }
-}
-
-impl DynamicType for Typed {
-    fn get_type(&self) -> Result<Cow<'_, Type>, TypeError> {
-        self.get_type()
-    }
-}
diff --git a/dhall/src/api/traits/mod.rs b/dhall/src/api/traits/mod.rs
index 315e17a..3fd21e4 100644
--- a/dhall/src/api/traits/mod.rs
+++ b/dhall/src/api/traits/mod.rs
@@ -1,6 +1,2 @@
 mod deserialize;
-mod dynamic_type;
-mod static_type;
 pub use deserialize::Deserialize;
-pub use dynamic_type::DynamicType;
-pub use static_type::{SimpleStaticType, StaticType};
diff --git a/dhall/src/api/traits/static_type.rs b/dhall/src/api/traits/static_type.rs
deleted file mode 100644
index e05dfff..0000000
--- a/dhall/src/api/traits/static_type.rs
+++ /dev/null
@@ -1,149 +0,0 @@
-use crate::phase::*;
-use dhall_proc_macros as dhall;
-use dhall_syntax::*;
-
-/// A value that has a statically-known Dhall type.
-///
-/// This trait is strictly more general than [SimpleStaticType].
-/// The reason is that it allows an arbitrary [Type] to be returned
-/// instead of just a [SimpleType].
-///
-/// For now the only interesting impl is [SimpleType] itself, who
-/// has a statically-known type which is not itself a [SimpleType].
-pub trait StaticType {
-    fn get_static_type() -> Type;
-}
-
-/// A Rust type that can be represented as a Dhall type.
-///
-/// A typical example is `Option<bool>`,
-/// represented by the dhall expression `Optional Bool`.
-///
-/// This trait can and should be automatically derived.
-///
-/// The representation needs to be independent of the value.
-/// For this reason, something like `HashMap<String, bool>` cannot implement
-/// [SimpleStaticType] because each different value would
-/// have a different Dhall record type.
-///
-/// The `Simple` in `SimpleStaticType` indicates that the returned type is
-/// a [SimpleType].
-pub trait SimpleStaticType {
-    fn get_simple_static_type() -> SimpleType;
-}
-
-fn mktype(x: SubExpr<X, X>) -> SimpleType {
-    x.into()
-}
-
-impl<T: SimpleStaticType> StaticType for T {
-    fn get_static_type() -> Type {
-        crate::phase::Normalized::from_thunk_and_type(
-            crate::core::thunk::Thunk::from_normalized_expr(
-                T::get_simple_static_type().into(),
-            ),
-            Type::const_type(),
-        )
-        .to_type()
-    }
-}
-
-impl StaticType for SimpleType {
-    /// By definition, a [SimpleType] has type `Type`.
-    /// This returns the Dhall expression `Type`
-    fn get_static_type() -> Type {
-        Type::const_type()
-    }
-}
-
-impl SimpleStaticType for bool {
-    fn get_simple_static_type() -> SimpleType {
-        mktype(dhall::subexpr!(Bool))
-    }
-}
-
-impl SimpleStaticType for Natural {
-    fn get_simple_static_type() -> SimpleType {
-        mktype(dhall::subexpr!(Natural))
-    }
-}
-
-impl SimpleStaticType for u32 {
-    fn get_simple_static_type() -> SimpleType {
-        mktype(dhall::subexpr!(Natural))
-    }
-}
-
-impl SimpleStaticType for u64 {
-    fn get_simple_static_type() -> SimpleType {
-        mktype(dhall::subexpr!(Natural))
-    }
-}
-
-impl SimpleStaticType for Integer {
-    fn get_simple_static_type() -> SimpleType {
-        mktype(dhall::subexpr!(Integer))
-    }
-}
-
-impl SimpleStaticType for i32 {
-    fn get_simple_static_type() -> SimpleType {
-        mktype(dhall::subexpr!(Integer))
-    }
-}
-
-impl SimpleStaticType for i64 {
-    fn get_simple_static_type() -> SimpleType {
-        mktype(dhall::subexpr!(Integer))
-    }
-}
-
-impl SimpleStaticType for String {
-    fn get_simple_static_type() -> SimpleType {
-        mktype(dhall::subexpr!(Text))
-    }
-}
-
-impl<A: SimpleStaticType, B: SimpleStaticType> SimpleStaticType for (A, B) {
-    fn get_simple_static_type() -> SimpleType {
-        let ta: SubExpr<_, _> = A::get_simple_static_type().into();
-        let tb: SubExpr<_, _> = B::get_simple_static_type().into();
-        mktype(dhall::subexpr!({ _1: ta, _2: tb }))
-    }
-}
-
-impl<T: SimpleStaticType> SimpleStaticType for Option<T> {
-    fn get_simple_static_type() -> SimpleType {
-        let t: SubExpr<_, _> = T::get_simple_static_type().into();
-        mktype(dhall::subexpr!(Optional t))
-    }
-}
-
-impl<T: SimpleStaticType> SimpleStaticType for Vec<T> {
-    fn get_simple_static_type() -> SimpleType {
-        let t: SubExpr<_, _> = T::get_simple_static_type().into();
-        mktype(dhall::subexpr!(List t))
-    }
-}
-
-impl<'a, T: SimpleStaticType> SimpleStaticType for &'a T {
-    fn get_simple_static_type() -> SimpleType {
-        T::get_simple_static_type()
-    }
-}
-
-impl<T> SimpleStaticType for std::marker::PhantomData<T> {
-    fn get_simple_static_type() -> SimpleType {
-        mktype(dhall::subexpr!({}))
-    }
-}
-
-impl<T: SimpleStaticType, E: SimpleStaticType> SimpleStaticType
-    for std::result::Result<T, E>
-{
-    fn get_simple_static_type() -> SimpleType {
-        let tt: SubExpr<_, _> = T::get_simple_static_type().into();
-        let te: SubExpr<_, _> = E::get_simple_static_type().into();
-        mktype(dhall::subexpr!(< Ok: tt | Err: te>))
-    }
-}
diff --git a/dhall/src/lib.rs b/dhall/src/lib.rs
index b35b2ae..c25fc82 100644
--- a/dhall/src/lib.rs
+++ b/dhall/src/lib.rs
@@ -35,15 +35,15 @@
 //! ### Custom datatype
 //!
 //! If you have a custom datatype for which you derived [serde::Deserialize], chances are
-//! you will be able to derive [SimpleStaticType][de::SimpleStaticType] for it as well.
+//! you will be able to derive [StaticType][de::StaticType] for it as well.
 //! This gives you access to a dhall representation of your datatype that can be outputted
 //! to users, and allows easy type-safe deserializing.
 //!
 //! ```edition2018
 //! use serde::Deserialize;
-//! use dhall::de::SimpleStaticType;
+//! use dhall::de::StaticType;
 //!
-//! #[derive(Debug, Deserialize, SimpleStaticType)]
+//! #[derive(Debug, Deserialize, StaticType)]
 //! struct Point {
 //!     x: u64,
 //!     y: u64,
@@ -68,7 +68,7 @@
 //! If you used to consume JSON or YAML in a loosely typed way, you can continue to do so
 //! with dhall. You only need to replace [serde_json::from_str] or [serde_yaml::from_str]
 //! with [dhall::de::from_str][de::from_str].
-//! More generally, if the [SimpleStaticType][de::SimpleStaticType] derive doesn't suit your
+//! More generally, if the [StaticType][de::StaticType] derive doesn't suit your
 //! needs, you can still deserialize any valid dhall file that serde can handle.
 //!
 //! [serde_json::from_str]: https://docs.serde.rs/serde_json/de/fn.from_str.html
@@ -130,4 +130,4 @@ pub mod error;
 pub(crate) mod phase;
 pub(crate) use api::traits;
 
-pub use api::de;
+pub use api::*;
diff --git a/dhall/src/phase/mod.rs b/dhall/src/phase/mod.rs
index af39eb6..5262a27 100644
--- a/dhall/src/phase/mod.rs
+++ b/dhall/src/phase/mod.rs
@@ -49,19 +49,6 @@ pub(crate) enum Typed {
 #[derive(Debug, Clone)]
 pub(crate) struct Normalized(pub(crate) Typed);
 
-/// A Dhall expression representing a simple type.
-///
-/// This captures what is usually simply called a "type", like
-/// `Bool`, `{ x: Integer }` or `Natural -> Text`.
-///
-/// For a more general notion of "type", see [Type].
-#[derive(Debug, Clone)]
-pub struct SimpleType(pub(crate) NormalizedSubExpr);
-
-/// A Dhall expression representing a (possibly higher-kinded) type.
-///
-/// This includes [SimpleType]s but also higher-kinded expressions like
-/// `Type`, `Kind` and `{ x: Type }`.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Type(pub(crate) Typed);
 
@@ -131,6 +118,12 @@ impl Typed {
     pub(crate) fn from_const(c: Const) -> Self {
         Typed::Const(c)
     }
+    pub(crate) fn from_value_untyped(v: Value) -> Self {
+        Typed::Untyped(Thunk::from_value(v))
+    }
+    pub(crate) fn from_normalized_expr_untyped(e: NormalizedSubExpr) -> Self {
+        Typed::from_thunk_untyped(Thunk::from_normalized_expr(e))
+    }
 
     // TODO: Avoid cloning if possible
     pub(crate) fn to_value(&self) -> Value {
@@ -179,6 +172,7 @@ impl Typed {
 }
 
 impl Type {
+    // Deprecated
     pub(crate) fn to_normalized(&self) -> Normalized {
         self.0.clone().normalize()
     }
@@ -202,19 +196,12 @@ impl Type {
         self.0.get_type()
     }
 
-    pub(crate) fn const_type() -> Self {
-        Type::from_const(Const::Type)
-    }
     pub(crate) fn from_const(c: Const) -> Self {
         Type(Typed::from_const(c))
     }
 }
 
 impl Normalized {
-    pub(crate) fn from_thunk_and_type(th: Thunk, t: Type) -> Self {
-        Normalized(Typed::from_thunk_and_type(th, t))
-    }
-
     pub(crate) fn to_expr(&self) -> NormalizedSubExpr {
         self.0.to_expr()
     }
@@ -225,9 +212,12 @@ impl Normalized {
     pub(crate) fn to_value(&self) -> Value {
         self.0.to_value()
     }
-    pub(crate) fn to_type(self) -> Type {
+    pub(crate) fn to_type(&self) -> Type {
         self.0.to_type()
     }
+    pub(crate) fn into_typed(self) -> Typed {
+        self.0
+    }
     pub(crate) fn get_type(&self) -> Result<Cow<'_, Type>, TypeError> {
         self.0.get_type()
     }
@@ -301,7 +291,6 @@ macro_rules! derive_traits_for_wrapper_struct {
 derive_traits_for_wrapper_struct!(Parsed);
 derive_traits_for_wrapper_struct!(Resolved);
 derive_traits_for_wrapper_struct!(Normalized);
-derive_traits_for_wrapper_struct!(SimpleType);
 
 impl Eq for Typed {}
 impl PartialEq for Typed {
@@ -321,27 +310,3 @@ impl Display for Type {
         self.to_normalized().fmt(f)
     }
 }
-
-// Exposed for the macros
-#[doc(hidden)]
-impl From<SimpleType> for NormalizedSubExpr {
-    fn from(x: SimpleType) -> NormalizedSubExpr {
-        x.0
-    }
-}
-
-// Exposed for the macros
-#[doc(hidden)]
-impl From<NormalizedSubExpr> for SimpleType {
-    fn from(x: NormalizedSubExpr) -> SimpleType {
-        SimpleType(x)
-    }
-}
-
-// Exposed for the macros
-#[doc(hidden)]
-impl From<Normalized> for Typed {
-    fn from(x: Normalized) -> Typed {
-        x.0
-    }
-}
diff --git a/dhall/src/phase/typecheck.rs b/dhall/src/phase/typecheck.rs
index e1dffb0..7f988c8 100644
--- a/dhall/src/phase/typecheck.rs
+++ b/dhall/src/phase/typecheck.rs
@@ -391,7 +391,7 @@ fn type_with(
             let e = e.rewrap(Annot(x, t));
             return type_with(ctx, e);
         }
-        Embed(p) => p.clone().into(),
+        Embed(p) => p.clone().into_typed(),
         Var(var) => match ctx.lookup(&var) {
             Some(typed) => typed,
             None => {