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

use super::*;

#[derive(Debug, Clone, Eq, PartialEq, Hash)]
pub enum ConstExpr {
    /// A function call
    ///
    /// The first field resolves to the function itself,
    /// and the second field is the list of arguments
    Call(Box<ConstExpr>, Vec<ConstExpr>),

    /// A binary operation (For example: `a + b`, `a * b`)
    Binary(BinOp, Box<ConstExpr>, Box<ConstExpr>),

    /// A unary operation (For example: `!x`, `*x`)
    Unary(UnOp, Box<ConstExpr>),

    /// A literal (For example: `1`, `"foo"`)
    Lit(Lit),

    /// A cast (`foo as f64`)
    Cast(Box<ConstExpr>, Box<Ty>),

    /// Variable reference, possibly containing `::` and/or type
    /// parameters, e.g. foo::bar::<baz>.
    Path(Path),

    /// An indexing operation (`foo[2]`)
    Index(Box<ConstExpr>, Box<ConstExpr>),

    /// No-op: used solely so we can pretty-print faithfully
    Paren(Box<ConstExpr>),

    /// If compiling with full support for expression syntax, any expression is
    /// allowed
    Other(Other),
}

#[cfg(not(feature = "full"))]
#[derive(Debug, Clone, Eq, PartialEq, Hash)]
pub struct Other {
    _private: (),
}

#[cfg(feature = "full")]
pub type Other = Expr;

#[cfg(feature = "parsing")]
pub mod parsing {
    use super::*;
    use {BinOp, Ty};
    use lit::parsing::lit;
    use op::parsing::{binop, unop};
    use ty::parsing::{path, ty};

    named!(pub const_expr -> ConstExpr, do_parse!(
        mut e: alt!(
            expr_unary
            |
            expr_lit
            |
            expr_path
            |
            expr_paren
            // Cannot handle ConstExpr::Other here because for example
            // `[u32; n!()]` would end up successfully parsing `n` as
            // ConstExpr::Path and then fail to parse `!()`. Instead, callers
            // are required to handle Other. See ty::parsing::array_len and
            // data::parsing::discriminant.
        ) >>
        many0!(alt!(
            tap!(args: and_call => {
                e = ConstExpr::Call(Box::new(e), args);
            })
            |
            tap!(more: and_binary => {
                let (op, other) = more;
                e = ConstExpr::Binary(op, Box::new(e), Box::new(other));
            })
            |
            tap!(ty: and_cast => {
                e = ConstExpr::Cast(Box::new(e), Box::new(ty));
            })
            |
            tap!(i: and_index => {
                e = ConstExpr::Index(Box::new(e), Box::new(i));
            })
        )) >>
        (e)
    ));

    named!(and_call -> Vec<ConstExpr>, do_parse!(
        punct!("(") >>
        args: terminated_list!(punct!(","), const_expr) >>
        punct!(")") >>
        (args)
    ));

    named!(and_binary -> (BinOp, ConstExpr), tuple!(binop, const_expr));

    named!(expr_unary -> ConstExpr, do_parse!(
        operator: unop >>
        operand: const_expr >>
        (ConstExpr::Unary(operator, Box::new(operand)))
    ));

    named!(expr_lit -> ConstExpr, map!(lit, ConstExpr::Lit));

    named!(expr_path -> ConstExpr, map!(path, ConstExpr::Path));

    named!(and_index -> ConstExpr, delimited!(punct!("["), const_expr, punct!("]")));

    named!(expr_paren -> ConstExpr, do_parse!(
        punct!("(") >>
        e: const_expr >>
        punct!(")") >>
        (ConstExpr::Paren(Box::new(e)))
    ));

    named!(and_cast -> Ty, do_parse!(
        keyword!("as") >>
        ty: ty >>
        (ty)
    ));
}

#[cfg(feature = "printing")]
mod printing {
    use super::*;
    use quote::{Tokens, ToTokens};

    impl ToTokens for ConstExpr {
        fn to_tokens(&self, tokens: &mut Tokens) {
            match *self {
                ConstExpr::Call(ref func, ref args) => {
                    func.to_tokens(tokens);
                    tokens.append("(");
                    tokens.append_separated(args, ",");
                    tokens.append(")");
                }
                ConstExpr::Binary(op, ref left, ref right) => {
                    left.to_tokens(tokens);
                    op.to_tokens(tokens);
                    right.to_tokens(tokens);
                }
                ConstExpr::Unary(op, ref expr) => {
                    op.to_tokens(tokens);
                    expr.to_tokens(tokens);
                }
                ConstExpr::Lit(ref lit) => lit.to_tokens(tokens),
                ConstExpr::Cast(ref expr, ref ty) => {
                    expr.to_tokens(tokens);
                    tokens.append("as");
                    ty.to_tokens(tokens);
                }
                ConstExpr::Path(ref path) => path.to_tokens(tokens),
                ConstExpr::Index(ref expr, ref index) => {
                    expr.to_tokens(tokens);
                    tokens.append("[");
                    index.to_tokens(tokens);
                    tokens.append("]");
                }
                ConstExpr::Paren(ref expr) => {
                    tokens.append("(");
                    expr.to_tokens(tokens);
                    tokens.append(")");
                }
                ConstExpr::Other(ref other) => {
                    other.to_tokens(tokens);
                }
            }
        }
    }

    #[cfg(not(feature = "full"))]
    impl ToTokens for Other {
        fn to_tokens(&self, _tokens: &mut Tokens) {
            unreachable!()
        }
    }
}