summaryrefslogtreecommitdiff
path: root/dhall/src/syntax/ast/expr.rs
blob: 6ba66499a2f4e58f6b59d25e423387167d162b62 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
use std::collections::BTreeMap;

use crate::semantics::Universe;
use crate::syntax::map::{DupTreeMap, DupTreeSet};
use crate::syntax::visitor;
use crate::syntax::*;

pub type Integer = isize;
pub type Natural = usize;
pub type Double = NaiveDouble;

/// Double with bitwise equality
#[derive(Debug, Copy, Clone)]
pub struct NaiveDouble(f64);

/// Constants for a pure type system
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum Const {
    Type,
    Kind,
    Sort,
}

impl Const {
    pub fn to_universe(self) -> Universe {
        Universe::from_const(self)
    }
}

/// Bound variable
///
/// The `Label` field is the variable's name (i.e. \"`x`\").
/// The `Int` field is a DeBruijn index.
/// See dhall-lang/standard/semantics.md for details
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct V(pub Label, pub usize);

// Definition order must match precedence order for
// pretty-printing to work correctly
#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum BinOp {
    /// `x ? y`
    ImportAlt,
    /// `x || y`
    BoolOr,
    /// `x + y`
    NaturalPlus,
    /// `x ++ y`
    TextAppend,
    /// `x # y`
    ListAppend,
    /// `x && y`
    BoolAnd,
    /// `x ∧ y`
    RecursiveRecordMerge,
    /// `x ⫽ y`
    RightBiasedRecordMerge,
    /// `x ⩓ y`
    RecursiveRecordTypeMerge,
    /// `x * y`
    NaturalTimes,
    /// `x == y`
    BoolEQ,
    /// `x != y`
    BoolNE,
    /// x === y
    Equivalence,
}

/// Built-ins
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub enum Builtin {
    Bool,
    Natural,
    Integer,
    Double,
    Text,
    List,
    Optional,
    OptionalNone,
    NaturalBuild,
    NaturalFold,
    NaturalIsZero,
    NaturalEven,
    NaturalOdd,
    NaturalToInteger,
    NaturalShow,
    NaturalSubtract,
    IntegerToDouble,
    IntegerShow,
    IntegerNegate,
    IntegerClamp,
    DoubleShow,
    ListBuild,
    ListFold,
    ListLength,
    ListHead,
    ListLast,
    ListIndexed,
    ListReverse,
    OptionalFold,
    OptionalBuild,
    TextShow,
}

// Each node carries an annotation.
#[derive(Debug, Clone)]
pub struct Expr {
    kind: Box<ExprKind<Expr>>,
    span: Span,
}

pub type UnspannedExpr = ExprKind<Expr>;

/// Numeric literals
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum NumKind {
    ///  `True`
    Bool(bool),
    ///  `1`
    Natural(Natural),
    ///  `+2`
    Integer(Integer),
    ///  `3.24`
    Double(Double),
}

/// Syntax tree for expressions
// Having the recursion out of the enum definition enables writing
// much more generic code and improves pattern-matching behind
// smart pointers.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum ExprKind<SubExpr> {
    Const(Const),
    Num(NumKind),
    ///  `x`
    ///  `x@n`
    Var(V),
    ///  `λ(x : A) -> b`
    Lam(Label, SubExpr, SubExpr),
    ///  `A -> B`
    ///  `∀(x : A) -> B`
    Pi(Label, SubExpr, SubExpr),
    ///  `f a`
    App(SubExpr, SubExpr),
    ///  `let x     = r in e`
    ///  `let x : t = r in e`
    Let(Label, Option<SubExpr>, SubExpr, SubExpr),
    ///  `x : t`
    Annot(SubExpr, SubExpr),
    ///  `assert : t`
    Assert(SubExpr),
    /// Built-in values
    Builtin(Builtin),
    // Binary operations
    BinOp(BinOp, SubExpr, SubExpr),
    ///  `if x then y else z`
    BoolIf(SubExpr, SubExpr, SubExpr),
    ///  `"Some ${interpolated} text"`
    TextLit(InterpolatedText<SubExpr>),
    ///  `[] : t`
    EmptyListLit(SubExpr),
    ///  `[x, y, z]`
    NEListLit(Vec<SubExpr>),
    ///  `Some e`
    SomeLit(SubExpr),
    ///  `{ k1 : t1, k2 : t1 }`
    RecordType(DupTreeMap<Label, SubExpr>),
    ///  `{ k1 = v1, k2 = v2 }`
    RecordLit(BTreeMap<Label, SubExpr>),
    ///  `< k1 : t1, k2 >`
    UnionType(DupTreeMap<Label, Option<SubExpr>>),
    ///  `merge x y : t`
    Merge(SubExpr, SubExpr, Option<SubExpr>),
    ///  `toMap x : t`
    ToMap(SubExpr, Option<SubExpr>),
    ///  `e.x`
    Field(SubExpr, Label),
    ///  `e.{ x, y, z }`
    Projection(SubExpr, DupTreeSet<Label>),
    ///  `e.(t)`
    ProjectionByExpr(SubExpr, SubExpr),
    ///  `x::y`
    Completion(SubExpr, SubExpr),
    /// `./some/path`
    Import(Import<SubExpr>),
}

impl<SE> ExprKind<SE> {
    pub fn traverse_ref_maybe_binder<'a, SE2, Err>(
        &'a self,
        visit: impl FnMut(Option<&'a Label>, &'a SE) -> Result<SE2, Err>,
    ) -> Result<ExprKind<SE2>, Err> {
        visitor::visit_ref(self, visit)
    }

    pub fn traverse_ref_with_special_handling_of_binders<'a, SE2, Err>(
        &'a self,
        mut visit_subexpr: impl FnMut(&'a SE) -> Result<SE2, Err>,
        mut visit_under_binder: impl FnMut(&'a Label, &'a SE) -> Result<SE2, Err>,
    ) -> Result<ExprKind<SE2>, Err> {
        self.traverse_ref_maybe_binder(|l, x| match l {
            None => visit_subexpr(x),
            Some(l) => visit_under_binder(l, x),
        })
    }

    pub fn traverse_ref<'a, SE2, Err>(
        &'a self,
        mut visit_subexpr: impl FnMut(&'a SE) -> Result<SE2, Err>,
    ) -> Result<ExprKind<SE2>, Err> {
        self.traverse_ref_maybe_binder(|_, e| visit_subexpr(e))
    }

    pub fn map_ref_maybe_binder<'a, SE2>(
        &'a self,
        mut map: impl FnMut(Option<&'a Label>, &'a SE) -> SE2,
    ) -> ExprKind<SE2> {
        trivial_result(self.traverse_ref_maybe_binder(|l, x| Ok(map(l, x))))
    }

    pub fn map_ref_with_special_handling_of_binders<'a, SE2>(
        &'a self,
        mut map_subexpr: impl FnMut(&'a SE) -> SE2,
        mut map_under_binder: impl FnMut(&'a Label, &'a SE) -> SE2,
    ) -> ExprKind<SE2> {
        self.map_ref_maybe_binder(|l, x| match l {
            None => map_subexpr(x),
            Some(l) => map_under_binder(l, x),
        })
    }

    pub fn map_ref<'a, SE2>(
        &'a self,
        mut map_subexpr: impl FnMut(&'a SE) -> SE2,
    ) -> ExprKind<SE2> {
        self.map_ref_maybe_binder(|_, e| map_subexpr(e))
    }
}

impl Expr {
    pub fn as_ref(&self) -> &UnspannedExpr {
        &self.kind
    }
    pub fn kind(&self) -> &UnspannedExpr {
        &self.kind
    }
    pub fn span(&self) -> Span {
        self.span.clone()
    }

    pub fn new(kind: UnspannedExpr, span: Span) -> Self {
        Expr {
            kind: Box::new(kind),
            span,
        }
    }
}

// Empty enum to indicate that no error can occur
pub(crate) enum X {}
pub(crate) fn trivial_result<T>(x: Result<T, X>) -> T {
    match x {
        Ok(x) => x,
        Err(e) => match e {},
    }
}

impl PartialEq for NaiveDouble {
    fn eq(&self, other: &Self) -> bool {
        self.0.to_bits() == other.0.to_bits()
    }
}

impl Eq for NaiveDouble {}

impl std::hash::Hash for NaiveDouble {
    fn hash<H>(&self, state: &mut H)
    where
        H: std::hash::Hasher,
    {
        self.0.to_bits().hash(state)
    }
}

impl From<f64> for NaiveDouble {
    fn from(x: f64) -> Self {
        NaiveDouble(x)
    }
}

impl From<NaiveDouble> for f64 {
    fn from(x: NaiveDouble) -> f64 {
        x.0
    }
}

impl From<Label> for V {
    fn from(x: Label) -> V {
        V(x, 0)
    }
}

impl std::cmp::PartialEq for Expr {
    fn eq(&self, other: &Self) -> bool {
        self.kind == other.kind
    }
}

impl std::cmp::Eq for Expr {}

impl std::hash::Hash for Expr {
    fn hash<H>(&self, state: &mut H)
    where
        H: std::hash::Hasher,
    {
        self.kind.hash(state)
    }
}