Considerably remove clutter in normalize

2 files changed, 107 insertions, 142 deletions

diff --git a/dhall_core/src/core.rs b/dhall_core/src/core.rs
index 6795c2c..675345e 100644
--- a/dhall_core/src/core.rs
+++ b/dhall_core/src/core.rs
@@ -231,6 +231,17 @@ impl<'i, S, A> From<Builtin> for Expr<'i, S, A> {
 }
 
 impl<'i, S, A> Expr<'i, S, A> {
+    pub fn map_shallow<T, F1, F2>(&self, map_expr: F1, map_note: F2) -> Expr<'i, T, A>
+    where
+        A: Clone,
+        T: Clone,
+        S: Clone,
+        F1: Fn(&Self) -> Expr<'i, T, A>,
+        F2: FnOnce(&S) -> T,
+    {
+        map_shallow(self, map_expr, map_note)
+    }
+
     pub fn bool_lit(&self) -> Option<bool> {
         match *self {
             Expr::BoolLit(v) => Some(v),
@@ -628,16 +639,71 @@ fn add_ui(u: usize, i: isize) -> usize {
     }
 }
 
-pub fn map_record_value<'a, I, K, V, U, F>(it: I, f: F) -> BTreeMap<K, U>
+pub fn map_shallow<'i, S, T, A, F1, F2>(e: &Expr<'i, S, A>, map: F1, map_note: F2) -> Expr<'i, T, A>
+where
+    A: Clone,
+    S: Clone,
+    T: Clone,
+    F1: Fn(&Expr<'i, S, A>) -> Expr<'i, T, A>,
+    F2: FnOnce(&S) -> T,
+{
+    use crate::Expr::*;
+    let bxmap = |x: &Expr<'i, S, A>| -> Box<Expr<'i, T, A>> { bx(map(x)) };
+    let opt = |x| map_opt_box(x, &map);
+    match *e {
+        Const(k) => Const(k),
+        Var(v) => Var(v),
+        Lam(x, ref t, ref b) => Lam(x, bxmap(t), bxmap(b)),
+        Pi(x, ref t, ref b) => Pi(x, bxmap(t), bxmap(b)),
+        App(ref f, ref a) => App(bxmap(f), bxmap(a)),
+        Let(l, ref t, ref a, ref b) => Let(l, opt(t), bxmap(a), bxmap(b)),
+        Annot(ref x, ref t) => Annot(bxmap(x), bxmap(t)),
+        Builtin(v) => Builtin(v),
+        BoolLit(b) => BoolLit(b),
+        BoolIf(ref b, ref t, ref f) => BoolIf(bxmap(b), bxmap(t), bxmap(f)),
+        NaturalLit(n) => NaturalLit(n),
+        IntegerLit(n) => IntegerLit(n),
+        DoubleLit(n) => DoubleLit(n),
+        TextLit(ref t) => TextLit(t.clone()),
+        BinOp(o, ref x, ref y) => BinOp(o, bxmap(x), bxmap(y)),
+        ListLit(ref t, ref es) => {
+            let es = es.iter().map(&map).collect();
+            ListLit(opt(t), es)
+        }
+        OptionalLit(ref t, ref es) => {
+            let es = es.iter().map(&map).collect();
+            OptionalLit(opt(t), es)
+        }
+        Record(ref kts) => Record(map_record_value(kts, map)),
+        RecordLit(ref kvs) => RecordLit(map_record_value(kvs, map)),
+        Union(ref kts) => Union(map_record_value(kts, map)),
+        UnionLit(k, ref v, ref kvs) => {
+            UnionLit(k, bxmap(v), map_record_value(kvs, map))
+        }
+        Merge(ref x, ref y, ref t) => Merge(bxmap(x), bxmap(y), opt(t)),
+        Field(ref r, x) => Field(bxmap(r), x),
+        Note(ref n, ref e) => Note(map_note(n), bxmap(e)),
+        Embed(ref a) => Embed(a.clone()),
+    }
+}
+
+pub fn map_record_value<'a, I, K, V, U, F>(it: I, mut f: F) -> BTreeMap<K, U>
 where
     I: IntoIterator<Item = (&'a K, &'a V)>,
     K: Eq + Ord + Copy + 'a,
     V: 'a,
-    F: Fn(&V) -> U,
+    F: FnMut(&V) -> U,
 {
     it.into_iter().map(|(&k, v)| (k, f(v))).collect()
 }
 
+pub fn map_opt_box<T, U, F>(x: &Option<Box<T>>, f: F) -> Option<Box<U>>
+where
+    F: FnOnce(&T) -> U,
+{
+    x.as_ref().map(|x| x.as_ref()).map(f).map(bx)
+}
+
 fn map_op2<T, U, V, F, G>(f: F, g: G, a: T, b: T) -> V
 where
     F: FnOnce(U, U) -> V,
@@ -916,4 +982,3 @@ where
 {
     map_op2(f, |x| bx(subst(v, e, x)), a, b)
 }
-
diff --git a/dhall_normalize/src/normalize.rs b/dhall_normalize/src/normalize.rs
index 2068ae3..0e46ee0 100644
--- a/dhall_normalize/src/normalize.rs
+++ b/dhall_normalize/src/normalize.rs
@@ -1,7 +1,7 @@
 #![allow(non_snake_case)]
-use std::fmt;
 use dhall_core::core::*;
 use dhall_generator::dhall;
+use std::fmt;
 
 /// Reduce an expression to its normal form, performing beta reduction
 ///
@@ -22,18 +22,20 @@ where
     use dhall_core::Builtin::*;
     use dhall_core::Expr::*;
     match *e {
-        Const(k) => Const(k),
-        Var(v) => Var(v),
-        Lam(x, ref tA, ref b) => {
-            let tA2 = normalize(tA);
-            let b2 = normalize(b);
-            Lam(x, bx(tA2), bx(b2))
-        }
-        Pi(x, ref tA, ref tB) => {
-            let tA2 = normalize(tA);
-            let tB2 = normalize(tB);
-            pi(x, tA2, tB2)
+        // Matches that don't normalize everything right away
+        Let(f, _, ref r, ref b) => {
+            let r2 = shift::<_, S, _>(1, V(f, 0), r);
+            let b2 = subst(V(f, 0), &r2, b);
+            let b3 = shift::<_, T, _>(-1, V(f, 0), &b2);
+            normalize(&b3)
         }
+        BoolIf(ref b, ref t, ref f) => match normalize(b) {
+            BoolLit(true) => normalize(t),
+            BoolLit(false) => normalize(f),
+            b2 => BoolIf(bx(b2), bx(normalize(t)), bx(normalize(f))),
+        },
+        Annot(ref x, _) => normalize(x),
+        Note(_, ref e) => normalize(e),
         App(ref f, ref a) => match normalize::<S, T, A>(f) {
             Lam(x, _A, b) => {
                 // Beta reduce
@@ -144,135 +146,33 @@ where
                 (f2, a2) => app(f2, a2),
             },
         },
-        Let(f, _, ref r, ref b) => {
-            let r2 = shift::<_, S, _>(1, V(f, 0), r);
-            let b2 = subst(V(f, 0), &r2, b);
-            let b3 = shift::<_, T, _>(-1, V(f, 0), &b2);
-            normalize(&b3)
-        }
-        Annot(ref x, _) => normalize(x),
-        Builtin(v) => Builtin(v),
-        BoolLit(b) => BoolLit(b),
-        BinOp(BoolAnd, ref x, ref y) => with_binop(
-            BoolAnd,
-            Expr::bool_lit,
-            |xn, yn| BoolLit(xn && yn),
-            normalize(x),
-            normalize(y),
-        ),
-        BinOp(BoolOr, ref x, ref y) => with_binop(
-            BoolOr,
-            Expr::bool_lit,
-            |xn, yn| BoolLit(xn || yn),
-            normalize(x),
-            normalize(y),
-        ),
-        BinOp(BoolEQ, ref x, ref y) => with_binop(
-            BoolEQ,
-            Expr::bool_lit,
-            |xn, yn| BoolLit(xn == yn),
-            normalize(x),
-            normalize(y),
-        ),
-        BinOp(BoolNE, ref x, ref y) => with_binop(
-            BoolNE,
-            Expr::bool_lit,
-            |xn, yn| BoolLit(xn != yn),
-            normalize(x),
-            normalize(y),
-        ),
-        BoolIf(ref b, ref t, ref f) => match normalize(b) {
-            BoolLit(true) => normalize(t),
-            BoolLit(false) => normalize(f),
-            b2 => BoolIf(bx(b2), bx(normalize(t)), bx(normalize(f))),
-        },
-        NaturalLit(n) => NaturalLit(n),
-        BinOp(NaturalPlus, ref x, ref y) => with_binop(
-            NaturalPlus,
-            Expr::natural_lit,
-            |xn, yn| NaturalLit(xn + yn),
-            normalize(x),
-            normalize(y),
-        ),
-        BinOp(NaturalTimes, ref x, ref y) => with_binop(
-            NaturalTimes,
-            Expr::natural_lit,
-            |xn, yn| NaturalLit(xn * yn),
-            normalize(x),
-            normalize(y),
-        ),
-        IntegerLit(n) => IntegerLit(n),
-        DoubleLit(n) => DoubleLit(n),
-        TextLit(ref t) => TextLit(t.clone()),
-        BinOp(TextAppend, ref x, ref y) => with_binop(
-            TextAppend,
-            Expr::text_lit,
-            |xt, yt| TextLit(xt + &yt),
-            normalize(x),
-            normalize(y),
-        ),
-        BinOp(ListAppend, ref x, ref y) => {
-            match (normalize(x), normalize(y)) {
-                (ListLit(t1, xs), ListLit(t2, ys)) => {
-                    // Drop type annotation if the result is not empty
-                    let t = if xs.len() == 0 && ys.len() == 0 {
-                        t1.or(t2)
-                    } else {
-                        None
-                    };
-                    let xs = xs.into_iter();
-                    let ys = ys.into_iter();
-                    ListLit(t, xs.chain(ys).collect())
-                }
-                (x, y) => BinOp(ListAppend, bx(x), bx(y)),
+
+        // Normalize everything else before matching
+        ref e => match e.map_shallow(normalize, |_| unreachable!()) {
+            BinOp(BoolAnd, box BoolLit(x), box BoolLit(y)) => BoolLit(x && y),
+            BinOp(BoolOr, box BoolLit(x), box BoolLit(y)) => BoolLit(x || y),
+            BinOp(BoolEQ, box BoolLit(x), box BoolLit(y)) => BoolLit(x == y),
+            BinOp(BoolNE, box BoolLit(x), box BoolLit(y)) => BoolLit(x != y),
+            BinOp(NaturalPlus, box NaturalLit(x), box NaturalLit(y)) => NaturalLit(x + y),
+            BinOp(NaturalTimes, box NaturalLit(x), box NaturalLit(y)) => NaturalLit(x * y),
+            BinOp(TextAppend, box TextLit(x), box TextLit(y)) => TextLit(x + &y),
+            BinOp(ListAppend, box ListLit(t1, xs), box ListLit(t2, ys)) => {
+                // Drop type annotation if the result is nonempty
+                let t = if xs.len() == 0 && ys.len() == 0 {
+                    t1.or(t2)
+                } else {
+                    None
+                };
+                let xs = xs.into_iter();
+                let ys = ys.into_iter();
+                ListLit(t, xs.chain(ys).collect())
             }
-        },
-        ListLit(ref t, ref es) => {
-            let t2 = t.as_ref().map(|x| x.as_ref()).map(normalize).map(bx);
-            let es2 = es.iter().map(normalize).collect();
-            ListLit(t2, es2)
-        }
-        OptionalLit(ref t, ref es) => {
-            let t2 = t.as_ref().map(|x| x.as_ref()).map(normalize).map(bx);
-            let es2 = es.iter().map(normalize).collect();
-            OptionalLit(t2, es2)
-        }
-        Record(ref kts) => Record(map_record_value(kts, normalize)),
-        RecordLit(ref kvs) => RecordLit(map_record_value(kvs, normalize)),
-        Union(ref kts) => Union(map_record_value(kts, normalize)),
-        UnionLit(k, ref v, ref kvs) => {
-            UnionLit(k, bx(normalize(v)), map_record_value(kvs, normalize))
-        }
-        Merge(ref _x, ref _y, ref _t) => unimplemented!(),
-        Field(ref r, x) => match normalize(r) {
-            RecordLit(kvs) => match kvs.get(x) {
-                Some(r2) => normalize(r2),
-                None => {
-                    Field(bx(RecordLit(map_record_value(&kvs, normalize))), x)
-                }
+            Merge(_x, _y, _t) => unimplemented!(),
+            Field(box RecordLit(kvs), x) => match kvs.get(x) {
+                Some(r) => r.clone(),
+                None => Field(bx(RecordLit(kvs)), x),
             },
-            r2 => Field(bx(r2), x),
+            e => e,
         },
-        Note(_, ref e) => normalize(e),
-        Embed(ref a) => Embed(a.clone()),
-        ref e => unimplemented!("{:?}", e),
-    }
-}
-
-fn with_binop<'a, S, A, U, Get, Set>(
-    op: BinOp,
-    get: Get,
-    set: Set,
-    x: Expr<'a, S, A>,
-    y: Expr<'a, S, A>,
-) -> Expr<'a, S, A>
-where
-    Get: Fn(&Expr<'a, S, A>) -> Option<U>,
-    Set: FnOnce(U, U) -> Expr<'a, S, A>,
-{
-    if let (Some(xv), Some(yv)) = (get(&x), get(&y)) {
-        set(xv, yv)
-    } else {
-        Expr::BinOp(op, bx(x), bx(y))
     }
 }