Move out conversion from value back to ast to its own file

5 files changed, 125 insertions, 91 deletions

diff --git a/dhall/src/semantics/core/value.rs b/dhall/src/semantics/core/value.rs
index 7403742..ad0861b 100644
--- a/dhall/src/semantics/core/value.rs
+++ b/dhall/src/semantics/core/value.rs
@@ -8,6 +8,7 @@ use crate::semantics::error::{TypeError, TypeMessage};
 use crate::semantics::phase::normalize::{apply_any, normalize_whnf};
 use crate::semantics::phase::typecheck::{builtin_to_value, const_to_value};
 use crate::semantics::phase::{NormalizedExpr, Typed};
+use crate::semantics::to_expr;
 use crate::syntax::{Builtin, Const, Span};
 
 #[derive(Debug, Clone, Copy)]
@@ -44,15 +45,6 @@ struct ValueInternal {
 #[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)))
@@ -174,9 +166,9 @@ impl Value {
     fn as_internal_mut(&self) -> RefMut<ValueInternal> {
         self.0.borrow_mut()
     }
-    /// WARNING: The returned ValueKind may be entirely unnormalized, in aprticular it may just be an
+    /// WARNING: The returned ValueKind may be entirely unnormalized, in particular it may just be an
     /// unevaled PartialExpr. You probably want to use `as_whnf`.
-    fn as_kind(&self) -> Ref<ValueKind> {
+    pub(crate) fn as_kind(&self) -> Ref<ValueKind> {
         Ref::map(self.as_internal(), ValueInternal::as_kind)
     }
     /// This is what you want if you want to pattern-match on the value.
@@ -187,11 +179,12 @@ impl Value {
         self.as_kind()
     }
 
-    pub(crate) fn to_expr(&self, opts: ToExprOptions) -> NormalizedExpr {
-        if opts.normalize {
-            self.normalize_whnf();
-        }
-        self.as_kind().to_expr(opts)
+    /// Converts a value back to the corresponding AST expression.
+    pub(crate) fn to_expr(
+        &self,
+        opts: to_expr::ToExprOptions,
+    ) -> NormalizedExpr {
+        to_expr::value_to_expr(self, opts)
     }
     pub(crate) fn to_whnf_ignore_type(&self) -> ValueKind {
         self.as_whnf().clone()
diff --git a/dhall/src/semantics/core/value_kind.rs b/dhall/src/semantics/core/value_kind.rs
index 36ba068..47df39d 100644
--- a/dhall/src/semantics/core/value_kind.rs
+++ b/dhall/src/semantics/core/value_kind.rs
@@ -1,10 +1,9 @@
 use std::collections::HashMap;
 
-use crate::semantics::core::value::{ToExprOptions, Value};
+use crate::semantics::core::value::Value;
 use crate::semantics::core::var::{AlphaLabel, AlphaVar, Shift, Subst};
-use crate::semantics::phase::typecheck::rc;
 use crate::semantics::phase::{Normalized, NormalizedExpr};
-use crate::syntax;
+use crate::semantics::to_expr;
 use crate::syntax::{
     Builtin, Const, ExprF, Integer, InterpolatedTextContents, Label,
     NaiveDouble, Natural,
@@ -52,77 +51,12 @@ impl ValueKind {
         Value::from_kind_and_type(self, t)
     }
 
-    pub(crate) fn to_expr(&self, opts: ToExprOptions) -> NormalizedExpr {
-        match self {
-            ValueKind::Lam(x, t, e) => rc(ExprF::Lam(
-                x.to_label_maybe_alpha(opts.alpha),
-                t.to_expr(opts),
-                e.to_expr(opts),
-            )),
-            ValueKind::AppliedBuiltin(b, args) => args
-                .iter()
-                .map(|v| v.to_expr(opts))
-                .fold(rc(ExprF::Builtin(*b)), |acc, v| rc(ExprF::App(acc, v))),
-            ValueKind::Pi(x, t, e) => rc(ExprF::Pi(
-                x.to_label_maybe_alpha(opts.alpha),
-                t.to_expr(opts),
-                e.to_expr(opts),
-            )),
-            ValueKind::Var(v) => rc(ExprF::Var(v.to_var(opts.alpha))),
-            ValueKind::Const(c) => rc(ExprF::Const(*c)),
-            ValueKind::BoolLit(b) => rc(ExprF::BoolLit(*b)),
-            ValueKind::NaturalLit(n) => rc(ExprF::NaturalLit(*n)),
-            ValueKind::IntegerLit(n) => rc(ExprF::IntegerLit(*n)),
-            ValueKind::DoubleLit(n) => rc(ExprF::DoubleLit(*n)),
-            ValueKind::EmptyOptionalLit(n) => rc(ExprF::App(
-                rc(ExprF::Builtin(Builtin::OptionalNone)),
-                n.to_expr(opts),
-            )),
-            ValueKind::NEOptionalLit(n) => rc(ExprF::SomeLit(n.to_expr(opts))),
-            ValueKind::EmptyListLit(n) => rc(ExprF::EmptyListLit(rc(
-                ExprF::App(rc(ExprF::Builtin(Builtin::List)), n.to_expr(opts)),
-            ))),
-            ValueKind::NEListLit(elts) => rc(ExprF::NEListLit(
-                elts.iter().map(|n| n.to_expr(opts)).collect(),
-            )),
-            ValueKind::RecordLit(kvs) => rc(ExprF::RecordLit(
-                kvs.iter()
-                    .map(|(k, v)| (k.clone(), v.to_expr(opts)))
-                    .collect(),
-            )),
-            ValueKind::RecordType(kts) => rc(ExprF::RecordType(
-                kts.iter()
-                    .map(|(k, v)| (k.clone(), v.to_expr(opts)))
-                    .collect(),
-            )),
-            ValueKind::UnionType(kts) => rc(ExprF::UnionType(
-                kts.iter()
-                    .map(|(k, v)| {
-                        (k.clone(), v.as_ref().map(|v| v.to_expr(opts)))
-                    })
-                    .collect(),
-            )),
-            ValueKind::UnionConstructor(l, kts) => rc(ExprF::Field(
-                ValueKind::UnionType(kts.clone()).to_expr(opts),
-                l.clone(),
-            )),
-            ValueKind::UnionLit(l, v, kts) => rc(ExprF::App(
-                ValueKind::UnionConstructor(l.clone(), kts.clone())
-                    .to_expr(opts),
-                v.to_expr(opts),
-            )),
-            ValueKind::TextLit(elts) => rc(ExprF::TextLit(
-                elts.iter()
-                    .map(|contents| contents.map_ref(|e| e.to_expr(opts)))
-                    .collect(),
-            )),
-            ValueKind::Equivalence(x, y) => rc(ExprF::BinOp(
-                syntax::BinOp::Equivalence,
-                x.to_expr(opts),
-                y.to_expr(opts),
-            )),
-            ValueKind::PartialExpr(e) => rc(e.map_ref(|v| v.to_expr(opts))),
-        }
+    /// Converts a value back to the corresponding AST expression.
+    pub(crate) fn to_expr(
+        &self,
+        opts: to_expr::ToExprOptions,
+    ) -> NormalizedExpr {
+        to_expr::kind_to_expr(self, opts)
     }
 
     pub(crate) fn normalize_mut(&mut self) {
diff --git a/dhall/src/semantics/mod.rs b/dhall/src/semantics/mod.rs
index 9d2e462..6438408 100644
--- a/dhall/src/semantics/mod.rs
+++ b/dhall/src/semantics/mod.rs
@@ -1,3 +1,4 @@
 pub mod core;
 pub mod error;
 pub mod phase;
+pub mod to_expr;
diff --git a/dhall/src/semantics/phase/mod.rs b/dhall/src/semantics/phase/mod.rs
index f27088c..6229d15 100644
--- a/dhall/src/semantics/phase/mod.rs
+++ b/dhall/src/semantics/phase/mod.rs
@@ -1,10 +1,11 @@
 use std::fmt::Display;
 use std::path::Path;
 
-use crate::semantics::core::value::{ToExprOptions, Value};
+use crate::semantics::core::value::Value;
 use crate::semantics::core::value_kind::ValueKind;
 use crate::semantics::core::var::{AlphaVar, Shift, Subst};
 use crate::semantics::error::{EncodeError, Error, ImportError, TypeError};
+use crate::semantics::to_expr::ToExprOptions;
 use crate::syntax::binary;
 use crate::syntax::{Builtin, Const, Expr};
 use resolve::ImportRoot;
@@ -101,18 +102,22 @@ impl Typed {
         Typed::from_const(Const::Type)
     }
 
+    /// Converts a value back to the corresponding AST expression.
     pub(crate) fn to_expr(&self) -> NormalizedExpr {
         self.0.to_expr(ToExprOptions {
             alpha: false,
             normalize: false,
         })
     }
+    /// Converts a value back to the corresponding AST expression, normalizing in the process.
     pub fn normalize_to_expr(&self) -> NormalizedExpr {
         self.0.to_expr(ToExprOptions {
             alpha: false,
             normalize: true,
         })
     }
+    /// Converts a value back to the corresponding AST expression, (akpha,beta)-normalizing in the
+    /// process.
     pub(crate) fn normalize_to_expr_alpha(&self) -> NormalizedExpr {
         self.0.to_expr(ToExprOptions {
             alpha: true,
diff --git a/dhall/src/semantics/to_expr.rs b/dhall/src/semantics/to_expr.rs
new file mode 100644
index 0000000..74bd2fe
--- /dev/null
+++ b/dhall/src/semantics/to_expr.rs
@@ -0,0 +1,101 @@
+use crate::semantics::core::value::Value;
+use crate::semantics::core::value_kind::ValueKind;
+use crate::semantics::phase::typecheck::rc;
+use crate::semantics::phase::NormalizedExpr;
+use crate::syntax;
+use crate::syntax::{Builtin, ExprF};
+
+#[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,
+}
+
+/// Converts a value back to the corresponding AST expression.
+pub(crate) fn value_to_expr(
+    val: &Value,
+    opts: ToExprOptions,
+) -> NormalizedExpr {
+    if opts.normalize {
+        val.normalize_whnf();
+    }
+    val.as_kind().to_expr(opts)
+}
+
+/// Converts a value back to the corresponding AST expression.
+pub(crate) fn kind_to_expr(
+    kind: &ValueKind,
+    opts: ToExprOptions,
+) -> NormalizedExpr {
+    match kind {
+        ValueKind::Lam(x, t, e) => rc(ExprF::Lam(
+            x.to_label_maybe_alpha(opts.alpha),
+            t.to_expr(opts),
+            e.to_expr(opts),
+        )),
+        ValueKind::AppliedBuiltin(b, args) => args
+            .iter()
+            .map(|v| v.to_expr(opts))
+            .fold(rc(ExprF::Builtin(*b)), |acc, v| rc(ExprF::App(acc, v))),
+        ValueKind::Pi(x, t, e) => rc(ExprF::Pi(
+            x.to_label_maybe_alpha(opts.alpha),
+            t.to_expr(opts),
+            e.to_expr(opts),
+        )),
+        ValueKind::Var(v) => rc(ExprF::Var(v.to_var(opts.alpha))),
+        ValueKind::Const(c) => rc(ExprF::Const(*c)),
+        ValueKind::BoolLit(b) => rc(ExprF::BoolLit(*b)),
+        ValueKind::NaturalLit(n) => rc(ExprF::NaturalLit(*n)),
+        ValueKind::IntegerLit(n) => rc(ExprF::IntegerLit(*n)),
+        ValueKind::DoubleLit(n) => rc(ExprF::DoubleLit(*n)),
+        ValueKind::EmptyOptionalLit(n) => rc(ExprF::App(
+            rc(ExprF::Builtin(Builtin::OptionalNone)),
+            n.to_expr(opts),
+        )),
+        ValueKind::NEOptionalLit(n) => rc(ExprF::SomeLit(n.to_expr(opts))),
+        ValueKind::EmptyListLit(n) => rc(ExprF::EmptyListLit(rc(ExprF::App(
+            rc(ExprF::Builtin(Builtin::List)),
+            n.to_expr(opts),
+        )))),
+        ValueKind::NEListLit(elts) => rc(ExprF::NEListLit(
+            elts.iter().map(|n| n.to_expr(opts)).collect(),
+        )),
+        ValueKind::RecordLit(kvs) => rc(ExprF::RecordLit(
+            kvs.iter()
+                .map(|(k, v)| (k.clone(), v.to_expr(opts)))
+                .collect(),
+        )),
+        ValueKind::RecordType(kts) => rc(ExprF::RecordType(
+            kts.iter()
+                .map(|(k, v)| (k.clone(), v.to_expr(opts)))
+                .collect(),
+        )),
+        ValueKind::UnionType(kts) => rc(ExprF::UnionType(
+            kts.iter()
+                .map(|(k, v)| (k.clone(), v.as_ref().map(|v| v.to_expr(opts))))
+                .collect(),
+        )),
+        ValueKind::UnionConstructor(l, kts) => rc(ExprF::Field(
+            ValueKind::UnionType(kts.clone()).to_expr(opts),
+            l.clone(),
+        )),
+        ValueKind::UnionLit(l, v, kts) => rc(ExprF::App(
+            ValueKind::UnionConstructor(l.clone(), kts.clone()).to_expr(opts),
+            v.to_expr(opts),
+        )),
+        ValueKind::TextLit(elts) => rc(ExprF::TextLit(
+            elts.iter()
+                .map(|contents| contents.map_ref(|e| e.to_expr(opts)))
+                .collect(),
+        )),
+        ValueKind::Equivalence(x, y) => rc(ExprF::BinOp(
+            syntax::BinOp::Equivalence,
+            x.to_expr(opts),
+            y.to_expr(opts),
+        )),
+        ValueKind::PartialExpr(e) => rc(e.map_ref(|v| v.to_expr(opts))),
+    }
+}