Merge pull request #124 from Nadrieril/catchup-spec

Catchup on standard changes

10 files changed, 209 insertions, 117 deletions

diff --git a/dhall/src/dhall.pest.visibility b/dhall/src/dhall.pest.visibility
index 17c1edc..03a000b 100644
--- a/dhall/src/dhall.pest.visibility
+++ b/dhall/src/dhall.pest.visibility
@@ -21,9 +21,14 @@ quoted_label
 # label
 # nonreserved_label
 # any_label
+any_label_or_some
 double_quote_chunk
 double_quote_escaped
 # unicode_escape
+# unicode_suffix
+# unbraced_escape
+# braced_codepoint
+# braced_escape
 double_quote_char
 double_quote_literal
 single_quote_continue
@@ -91,6 +96,7 @@ prefer
 lambda
 forall
 arrow
+# complete
 # exponent
 numeric_double_literal
 minus_infinity_literal
@@ -161,6 +167,7 @@ equivalent_expression
 application_expression
 first_application_expression
 # import_expression
+completion_expression
 selector_expression
 selector
 labels
diff --git a/dhall/src/error/mod.rs b/dhall/src/error/mod.rs
index 1288c12..6e7be64 100644
--- a/dhall/src/error/mod.rs
+++ b/dhall/src/error/mod.rs
@@ -67,7 +67,7 @@ pub(crate) enum TypeMessage {
     BinOpTypeMismatch(BinOp, Value),
     InvalidTextInterpolation(Value),
     Merge1ArgMustBeRecord(Value),
-    Merge2ArgMustBeUnion(Value),
+    Merge2ArgMustBeUnionOrOptional(Value),
     MergeEmptyNeedsAnnotation,
     MergeHandlerMissingVariant(Label),
     MergeVariantMissingHandler(Label),
@@ -76,6 +76,7 @@ pub(crate) enum TypeMessage {
     MergeHandlerReturnTypeMustNotBeDependent,
     ProjectionMustBeRecord,
     ProjectionMissingEntry,
+    ProjectionDuplicateField,
     Sort,
     RecordTypeDuplicateField,
     RecordTypeMergeRequiresRecordType(Value),
@@ -124,7 +125,7 @@ impl std::fmt::Display for TypeError {
                         y
                     ))
             }
-            _ => "Type error: Unhandled error".to_string(),
+            _ => format!("Type error: Unhandled error: {:?}", self.message),
         };
         write!(f, "{}", msg)
     }
diff --git a/dhall/src/semantics/phase/normalize.rs b/dhall/src/semantics/phase/normalize.rs
index d81a910..459eaf1 100644
--- a/dhall/src/semantics/phase/normalize.rs
+++ b/dhall/src/semantics/phase/normalize.rs
@@ -1,4 +1,5 @@
 use std::collections::HashMap;
+use std::convert::TryInto;
 
 use crate::semantics::core::value::Value;
 use crate::semantics::core::value::ValueKind;
@@ -141,6 +142,16 @@ pub(crate) fn apply_builtin(
             }
             _ => Ret::DoneAsIs,
         },
+        (IntegerNegate, [n]) => match &*n.as_whnf() {
+            IntegerLit(n) => Ret::ValueKind(IntegerLit(-n)),
+            _ => Ret::DoneAsIs,
+        },
+        (IntegerClamp, [n]) => match &*n.as_whnf() {
+            IntegerLit(n) => {
+                Ret::ValueKind(NaturalLit((*n).try_into().unwrap_or(0)))
+            }
+            _ => Ret::DoneAsIs,
+        },
         (DoubleShow, [n]) => {
             match &*n.as_whnf() {
                 DoubleLit(n) => Ret::ValueKind(TextLit(vec![
@@ -259,37 +270,23 @@ pub(crate) fn apply_builtin(
                 _ => Ret::DoneAsIs,
             }
         }
-        (ListBuild, [t, f]) => match &*f.as_whnf() {
-            // fold/build fusion
-            ValueKind::AppliedBuiltin(ListFold, args) => {
-                if args.len() >= 2 {
-                    Ret::Value(args[1].clone())
-                } else {
-                    // Do we really need to handle this case ?
-                    unimplemented!()
-                }
-            }
-            _ => {
-                let list_t = Value::from_builtin(List).app(t.clone());
-                Ret::Value(
-                    f.app(list_t.clone())
-                        .app({
-                            // Move `t` under new variables
-                            let t1 = t.under_binder(Label::from("x"));
-                            let t2 = t1.under_binder(Label::from("xs"));
-                            make_closure!(
-                                λ(x : #t) ->
-                                λ(xs : List #t1) ->
-                                [ var(x, 1, #t2) ] # var(xs, 0, List #t2)
-                            )
-                        })
-                        .app(
-                            EmptyListLit(t.clone())
-                                .into_value_with_type(list_t),
-                        ),
-                )
-            }
-        },
+        (ListBuild, [t, f]) => {
+            let list_t = Value::from_builtin(List).app(t.clone());
+            Ret::Value(
+                f.app(list_t.clone())
+                    .app({
+                        // Move `t` under new variables
+                        let t1 = t.under_binder(Label::from("x"));
+                        let t2 = t1.under_binder(Label::from("xs"));
+                        make_closure!(
+                            λ(x : #t) ->
+                            λ(xs : List #t1) ->
+                            [ var(x, 1, #t2) ] # var(xs, 0, List #t2)
+                        )
+                    })
+                    .app(EmptyListLit(t.clone()).into_value_with_type(list_t)),
+            )
+        }
         (ListFold, [_, l, _, cons, nil, r @ ..]) => match &*l.as_whnf() {
             EmptyListLit(_) => Ret::ValueWithRemainingArgs(r, nil.clone()),
             NEListLit(xs) => {
@@ -301,31 +298,20 @@ pub(crate) fn apply_builtin(
             }
             _ => Ret::DoneAsIs,
         },
-        (OptionalBuild, [t, f]) => match &*f.as_whnf() {
-            // fold/build fusion
-            ValueKind::AppliedBuiltin(OptionalFold, args) => {
-                if args.len() >= 2 {
-                    Ret::Value(args[1].clone())
-                } else {
-                    // Do we really need to handle this case ?
-                    unimplemented!()
-                }
-            }
-            _ => {
-                let optional_t = Value::from_builtin(Optional).app(t.clone());
-                Ret::Value(
-                    f.app(optional_t.clone())
-                        .app({
-                            let t1 = t.under_binder(Label::from("x"));
-                            make_closure!(λ(x: #t) -> Some(var(x, 0, #t1)))
-                        })
-                        .app(
-                            EmptyOptionalLit(t.clone())
-                                .into_value_with_type(optional_t),
-                        ),
-                )
-            }
-        },
+        (OptionalBuild, [t, f]) => {
+            let optional_t = Value::from_builtin(Optional).app(t.clone());
+            Ret::Value(
+                f.app(optional_t.clone())
+                    .app({
+                        let t1 = t.under_binder(Label::from("x"));
+                        make_closure!(λ(x: #t) -> Some(var(x, 0, #t1)))
+                    })
+                    .app(
+                        EmptyOptionalLit(t.clone())
+                            .into_value_with_type(optional_t),
+                    ),
+            )
+        }
         (OptionalFold, [_, v, _, just, nothing, r @ ..]) => match &*v.as_whnf()
         {
             EmptyOptionalLit(_) => {
@@ -336,27 +322,17 @@ pub(crate) fn apply_builtin(
             }
             _ => Ret::DoneAsIs,
         },
-        (NaturalBuild, [f]) => match &*f.as_whnf() {
-            // fold/build fusion
-            ValueKind::AppliedBuiltin(NaturalFold, args) => {
-                if !args.is_empty() {
-                    Ret::Value(args[0].clone())
-                } else {
-                    // Do we really need to handle this case ?
-                    unimplemented!()
-                }
-            }
-            _ => Ret::Value(
-                f.app(Value::from_builtin(Natural))
-                    .app(make_closure!(
-                        λ(x : Natural) -> 1 + var(x, 0, Natural)
-                    ))
-                    .app(
-                        NaturalLit(0)
-                            .into_value_with_type(Value::from_builtin(Natural)),
-                    ),
-            ),
-        },
+        (NaturalBuild, [f]) => Ret::Value(
+            f.app(Value::from_builtin(Natural))
+                .app(make_closure!(
+                    λ(x : Natural) -> 1 + var(x, 0, Natural)
+                ))
+                .app(
+                    NaturalLit(0)
+                        .into_value_with_type(Value::from_builtin(Natural)),
+                ),
+        ),
+
         (NaturalFold, [n, t, succ, zero, r @ ..]) => match &*n.as_whnf() {
             NaturalLit(0) => Ret::ValueWithRemainingArgs(r, zero.clone()),
             NaturalLit(n) => {
@@ -614,8 +590,8 @@ pub(crate) fn normalize_one_layer(
     ty: &Value,
 ) -> ValueKind {
     use ValueKind::{
-        AppliedBuiltin, BoolLit, DoubleLit, EmptyListLit, IntegerLit,
-        NEListLit, NEOptionalLit, NaturalLit, RecordLit, TextLit,
+        AppliedBuiltin, BoolLit, DoubleLit, EmptyListLit, EmptyOptionalLit,
+        IntegerLit, NEListLit, NEOptionalLit, NaturalLit, RecordLit, TextLit,
         UnionConstructor, UnionLit, UnionType,
     };
 
@@ -741,6 +717,7 @@ pub(crate) fn normalize_one_layer(
         ExprKind::ProjectionByExpr(_, _) => {
             unimplemented!("selection by expression")
         }
+        ExprKind::Completion(_, _) => unimplemented!("record completion"),
 
         ExprKind::Merge(ref handlers, ref variant, _) => {
             let handlers_borrow = handlers.as_whnf();
@@ -762,6 +739,26 @@ pub(crate) fn normalize_one_layer(
                         Ret::Expr(expr)
                     }
                 },
+                (RecordLit(kvs), EmptyOptionalLit(_)) => {
+                    match kvs.get(&"None".into()) {
+                        Some(h) => Ret::Value(h.clone()),
+                        None => {
+                            drop(handlers_borrow);
+                            drop(variant_borrow);
+                            Ret::Expr(expr)
+                        }
+                    }
+                }
+                (RecordLit(kvs), NEOptionalLit(v)) => {
+                    match kvs.get(&"Some".into()) {
+                        Some(h) => Ret::Value(h.app(v.clone())),
+                        None => {
+                            drop(handlers_borrow);
+                            drop(variant_borrow);
+                            Ret::Expr(expr)
+                        }
+                    }
+                }
                 _ => {
                     drop(handlers_borrow);
                     drop(variant_borrow);
diff --git a/dhall/src/semantics/phase/typecheck.rs b/dhall/src/semantics/phase/typecheck.rs
index c439f74..97502d4 100644
--- a/dhall/src/semantics/phase/typecheck.rs
+++ b/dhall/src/semantics/phase/typecheck.rs
@@ -1,3 +1,4 @@
+use std::borrow::Cow;
 use std::cmp::max;
 use std::collections::HashMap;
 
@@ -235,6 +236,9 @@ fn type_of_builtin<E>(b: Builtin) -> Expr<E> {
 
         IntegerToDouble => make_type!(Integer -> Double),
         IntegerShow => make_type!(Integer -> Text),
+        IntegerNegate => make_type!(Integer -> Integer),
+        IntegerClamp => make_type!(Integer -> Natural),
+
         DoubleShow => make_type!(Double -> Text),
         TextShow => make_type!(Text -> Text),
 
@@ -692,8 +696,19 @@ fn type_last_layer(
             let union_type = union.get_type()?;
             let union_borrow = union_type.as_whnf();
             let variants = match &*union_borrow {
-                ValueKind::UnionType(kts) => kts,
-                _ => return mkerr(Merge2ArgMustBeUnion(union.clone())),
+                ValueKind::UnionType(kts) => Cow::Borrowed(kts),
+                ValueKind::AppliedBuiltin(syntax::Builtin::Optional, args)
+                    if args.len() == 1 =>
+                {
+                    let ty = &args[0];
+                    let mut kts = HashMap::new();
+                    kts.insert("None".into(), None);
+                    kts.insert("Some".into(), Some(ty.clone()));
+                    Cow::Owned(kts)
+                }
+                _ => {
+                    return mkerr(Merge2ArgMustBeUnionOrOptional(union.clone()))
+                }
             };
 
             let mut inferred_type = None;
@@ -774,7 +789,15 @@ fn type_last_layer(
             for l in labels {
                 match kts.get(l) {
                     None => return mkerr(ProjectionMissingEntry),
-                    Some(t) => new_kts.insert(l.clone(), t.clone()),
+                    Some(t) => {
+                        use std::collections::hash_map::Entry;
+                        match new_kts.entry(l.clone()) {
+                            Entry::Occupied(_) => {
+                                return mkerr(ProjectionDuplicateField)
+                            }
+                            Entry::Vacant(e) => e.insert(t.clone()),
+                        }
+                    }
                 };
             }
 
@@ -784,6 +807,7 @@ fn type_last_layer(
             ))
         }
         ProjectionByExpr(_, _) => unimplemented!("selection by expression"),
+        Completion(_, _) => unimplemented!("record completion"),
     };
 
     Ok(match ret {
diff --git a/dhall/src/syntax/ast/expr.rs b/dhall/src/syntax/ast/expr.rs
index 48c48d8..68cb524 100644
--- a/dhall/src/syntax/ast/expr.rs
+++ b/dhall/src/syntax/ast/expr.rs
@@ -79,6 +79,8 @@ pub enum Builtin {
     NaturalSubtract,
     IntegerToDouble,
     IntegerShow,
+    IntegerNegate,
+    IntegerClamp,
     DoubleShow,
     ListBuild,
     ListFold,
@@ -163,6 +165,8 @@ pub enum ExprKind<SubExpr, Embed> {
     Projection(SubExpr, DupTreeSet<Label>),
     ///  `e.(t)`
     ProjectionByExpr(SubExpr, SubExpr),
+    ///  `x::y`
+    Completion(SubExpr, SubExpr),
     /// `./some/path`
     Import(Import<SubExpr>),
     /// Embeds the result of resolving an import
diff --git a/dhall/src/syntax/ast/visitor.rs b/dhall/src/syntax/ast/visitor.rs
index b557995..424048b 100644
--- a/dhall/src/syntax/ast/visitor.rs
+++ b/dhall/src/syntax/ast/visitor.rs
@@ -164,6 +164,9 @@ where
         ProjectionByExpr(e, x) => {
             ProjectionByExpr(v.visit_subexpr(e)?, v.visit_subexpr(x)?)
         }
+        Completion(e, x) => {
+            Completion(v.visit_subexpr(e)?, v.visit_subexpr(x)?)
+        }
         Assert(e) => Assert(v.visit_subexpr(e)?),
         Import(i) => Import(i.traverse_ref(|e| v.visit_subexpr(e))?),
         Embed(a) => Embed(v.visit_embed(a)?),
@@ -281,6 +284,10 @@ where
             v.visit_subexpr(e)?;
             v.visit_subexpr(x)?;
         }
+        Completion(x, y) => {
+            v.visit_subexpr(x)?;
+            v.visit_subexpr(y)?;
+        }
         Assert(e) => v.visit_subexpr(e)?,
         Import(i) => i.traverse_mut(|e| v.visit_subexpr(e))?,
         Embed(a) => v.visit_embed(a)?,
diff --git a/dhall/src/syntax/binary/decode.rs b/dhall/src/syntax/binary/decode.rs
index 254ab07..c18deb5 100644
--- a/dhall/src/syntax/binary/decode.rs
+++ b/dhall/src/syntax/binary/decode.rs
@@ -98,6 +98,11 @@ fn cbor_value_to_dhall(data: &cbor::Value) -> Result<DecodedExpr, DecodeError> {
                 let l = Label::from(l.as_str());
                 Pi(l, x, y)
             }
+            [U64(3), U64(13), x, y] => {
+                let x = cbor_value_to_dhall(&x)?;
+                let y = cbor_value_to_dhall(&y)?;
+                Completion(x, y)
+            }
             [U64(3), U64(n), x, y] => {
                 let x = cbor_value_to_dhall(&x)?;
                 let y = cbor_value_to_dhall(&y)?;
diff --git a/dhall/src/syntax/binary/encode.rs b/dhall/src/syntax/binary/encode.rs
index 25a545c..5e79f2d 100644
--- a/dhall/src/syntax/binary/encode.rs
+++ b/dhall/src/syntax/binary/encode.rs
@@ -164,6 +164,7 @@ where
         ProjectionByExpr(x, y) => {
             ser_seq!(ser; tag(10), expr(x), vec![expr(y)])
         }
+        Completion(x, y) => ser_seq!(ser; tag(3), tag(13), expr(x), expr(y)),
         Import(import) => serialize_import(ser, import),
         Embed(_) => unimplemented!(
             "An expression with resolved imports cannot be binary-encoded"
diff --git a/dhall/src/syntax/text/parser.rs b/dhall/src/syntax/text/parser.rs
index 832472b..feaa2a5 100644
--- a/dhall/src/syntax/text/parser.rs
+++ b/dhall/src/syntax/text/parser.rs
@@ -57,6 +57,8 @@ impl crate::syntax::Builtin {
             "Natural/subtract" => Some(NaturalSubtract),
             "Integer/toDouble" => Some(IntegerToDouble),
             "Integer/show" => Some(IntegerShow),
+            "Integer/negate" => Some(IntegerNegate),
+            "Integer/clamp" => Some(IntegerClamp),
             "Double/show" => Some(DoubleShow),
             "List/build" => Some(ListBuild),
             "List/fold" => Some(ListFold),
@@ -181,6 +183,15 @@ impl DhallParser {
         Ok(Label::from(input.as_str()))
     }
 
+    // TODO: waiting for https://github.com/dhall-lang/dhall-lang/pull/871
+    // #[alias(label)]
+    // fn any_label_or_some(input: ParseInput) -> ParseResult<Label> {
+    //     Ok(match_nodes!(input.into_children();
+    //         [label(l)] => l,
+    //         [Some_(_)] => Label::from("Some"),
+    //     ))
+    // }
+
     fn double_quote_literal(input: ParseInput) -> ParseResult<ParsedText> {
         Ok(match_nodes!(input.into_children();
             [double_quote_chunk(chunks)..] => {
@@ -215,19 +226,18 @@ impl DhallParser {
             "t" => "\t".to_owned(),
             // "uXXXX" or "u{XXXXX}"
             s => {
-                use std::convert::{TryFrom, TryInto};
+                use std::convert::TryInto;
 
                 let s = &s[1..];
                 let s = if &s[0..1] == "{" {
                     &s[1..s.len() - 1]
                 } else {
-                    &s[0..s.len()]
+                    s
                 };
 
                 if s.len() > 8 {
                     Err(input.error(format!(
-                        "Escape sequences can't have more than 8 chars: \"{}\"",
-                        s
+                        "Escape sequences can't have more than 8 chars"
                     )))?
                 }
 
@@ -240,12 +250,10 @@ impl DhallParser {
                 // `s` has length 8, so `bytes` has length 4
                 let bytes: &[u8] = &hex::decode(s).unwrap();
                 let i = u32::from_be_bytes(bytes.try_into().unwrap());
-                let c = char::try_from(i).unwrap();
                 match i {
-                    0xD800..=0xDFFF => {
-                        let c_ecapsed = c.escape_unicode();
-                        Err(input.error(format!("Escape sequences can't contain surrogate pairs: \"{}\"", c_ecapsed)))?
-                    }
+                    0xD800..=0xDFFF => Err(input.error(format!(
+                        "Escape sequences can't contain surrogate pairs"
+                    )))?,
                     0x0FFFE..=0x0FFFF
                     | 0x1FFFE..=0x1FFFF
                     | 0x2FFFE..=0x2FFFF
@@ -262,12 +270,12 @@ impl DhallParser {
                     | 0xDFFFE..=0xDFFFF
                     | 0xEFFFE..=0xEFFFF
                     | 0xFFFFE..=0xFFFFF
-                    | 0x10_FFFE..=0x10_FFFF => {
-                        let c_ecapsed = c.escape_unicode();
-                        Err(input.error(format!("Escape sequences can't contain non-characters: \"{}\"", c_ecapsed)))?
-                    }
+                    | 0x10_FFFE..=0x10_FFFF => Err(input.error(format!(
+                        "Escape sequences can't contain non-characters"
+                    )))?,
                     _ => {}
                 }
+                let c: char = i.try_into().unwrap();
                 std::iter::once(c).collect()
             }
         })
@@ -384,19 +392,27 @@ impl DhallParser {
     }
 
     fn natural_literal(input: ParseInput) -> ParseResult<Natural> {
-        input
-            .as_str()
-            .trim()
-            .parse()
-            .map_err(|e| input.error(format!("{}", e)))
+        let s = input.as_str().trim();
+        if s.starts_with("0x") {
+            let without_prefix = s.trim_start_matches("0x");
+            usize::from_str_radix(without_prefix, 16)
+                .map_err(|e| input.error(format!("{}", e)))
+        } else {
+            s.parse().map_err(|e| input.error(format!("{}", e)))
+        }
     }
 
     fn integer_literal(input: ParseInput) -> ParseResult<Integer> {
-        input
-            .as_str()
-            .trim()
-            .parse()
-            .map_err(|e| input.error(format!("{}", e)))
+        let s = input.as_str().trim();
+        let (sign, rest) = (&s[0..1], &s[1..]);
+        if rest.starts_with("0x") {
+            let without_prefix =
+                sign.to_owned() + rest.trim_start_matches("0x");
+            isize::from_str_radix(&without_prefix, 16)
+                .map_err(|e| input.error(format!("{}", e)))
+        } else {
+            s.parse().map_err(|e| input.error(format!("{}", e)))
+        }
     }
 
     #[alias(expression, shortcut = true)]
@@ -766,6 +782,25 @@ impl DhallParser {
     }
 
     #[alias(expression, shortcut = true)]
+    fn completion_expression(input: ParseInput) -> ParseResult<Expr> {
+        Ok(match_nodes!(input.children();
+            [expression(e)] => e,
+            [expression(first), expression(rest)..] => {
+                rest.fold(
+                    first,
+                    |acc, e| {
+                        spanned_union(
+                            acc.span(),
+                            e.span(),
+                            Completion(acc, e),
+                        )
+                    }
+                )
+            },
+        ))
+    }
+
+    #[alias(expression, shortcut = true)]
     fn selector_expression(input: ParseInput) -> ParseResult<Expr> {
         Ok(match_nodes!(input.children();
             [expression(e)] => e,
diff --git a/dhall/src/syntax/text/printer.rs b/dhall/src/syntax/text/printer.rs
index 78942ed..96f4c2a 100644
--- a/dhall/src/syntax/text/printer.rs
+++ b/dhall/src/syntax/text/printer.rs
@@ -64,6 +64,9 @@ impl<E: Display + Clone> UnspannedExpr<E> {
             Field(a, b) => Field(a.phase(Primitive), b),
             Projection(e, ls) => Projection(e.phase(Primitive), ls),
             ProjectionByExpr(a, b) => ProjectionByExpr(a.phase(Primitive), b),
+            Completion(a, b) => {
+                Completion(a.phase(Primitive), b.phase(Primitive))
+            }
             e => e,
         }
     }
@@ -89,9 +92,10 @@ impl<E: Display + Clone> UnspannedExpr<E> {
             // Precedence is magically handled by the ordering of BinOps.
             ExprKind::BinOp(op, _, _) => phase > PrintPhase::BinOp(*op),
             ExprKind::App(_, _) => phase > PrintPhase::App,
-            Field(_, _) | Projection(_, _) | ProjectionByExpr(_, _) => {
-                phase > PrintPhase::Import
-            }
+            Field(_, _)
+            | Projection(_, _)
+            | ProjectionByExpr(_, _)
+            | Completion(_, _) => phase > PrintPhase::Import,
             _ => false,
         };
 
@@ -189,13 +193,6 @@ impl<SE: Display + Clone, E: Display> Display for ExprKind<SE, E> {
             Field(a, b) => {
                 write!(f, "{}.{}", a, b)?;
             }
-            Projection(e, ls) => {
-                write!(f, "{}.", e)?;
-                fmt_list("{ ", ", ", " }", ls, f, Display::fmt)?;
-            }
-            ProjectionByExpr(a, b) => {
-                write!(f, "{}.({})", a, b)?;
-            }
             Var(a) => a.fmt(f)?,
             Const(k) => k.fmt(f)?,
             Builtin(v) => v.fmt(f)?,
@@ -224,6 +221,16 @@ impl<SE: Display + Clone, E: Display> Display for ExprKind<SE, E> {
                 }
                 Ok(())
             })?,
+            Projection(e, ls) => {
+                write!(f, "{}.", e)?;
+                fmt_list("{ ", ", ", " }", ls, f, Display::fmt)?;
+            }
+            ProjectionByExpr(a, b) => {
+                write!(f, "{}.({})", a, b)?;
+            }
+            Completion(a, b) => {
+                write!(f, "{}::{}", a, b)?;
+            }
             Import(a) => a.fmt(f)?,
             Embed(a) => a.fmt(f)?,
         }
@@ -322,6 +329,8 @@ impl Display for NaiveDouble {
             f.write_str("-Infinity")
         } else if v.is_nan() {
             f.write_str("NaN")
+        } else if v == 0.0 && v.is_sign_negative() {
+            f.write_str("-0.0")
         } else {
             let s = format!("{}", v);
             if s.contains('e') || s.contains('.') {
@@ -459,6 +468,8 @@ impl Display for Builtin {
             NaturalShow => "Natural/show",
             NaturalSubtract => "Natural/subtract",
             IntegerToDouble => "Integer/toDouble",
+            IntegerNegate => "Integer/negate",
+            IntegerClamp => "Integer/clamp",
             IntegerShow => "Integer/show",
             DoubleShow => "Double/show",
             ListBuild => "List/build",