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
extern crate proc_macro;
use proc_macro2::{Ident, Span, TokenStream, TokenTree};
use quote::quote;
use syn::{parse_macro_input, BinOp, Expr, ExprBinary, ExprMethodCall, ExprUnary, UnOp};
#[proc_macro]
pub fn checked_expr(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let input = parse_macro_input!(input as Expr);
let expr = expr(&input);
let tokens = quote! {
(|| Some(#expr) )()
};
tokens.into()
}
fn expr(expr: &Expr) -> TokenStream {
match expr {
Expr::Unary(expr) => unary_expr(expr),
Expr::Binary(expr) => binary_expr(expr),
Expr::Paren(expr) => crate::expr(&expr.expr),
Expr::MethodCall(expr) => method_call(expr),
_ => quote! {
(#expr)
},
}
}
fn binary_expr(expr: &ExprBinary) -> TokenStream {
let function_name = match expr.op {
BinOp::Add(_) => "checked_add",
BinOp::Sub(_) => "checked_sub",
BinOp::Mul(_) => "checked_mul",
BinOp::Div(_) => "checked_div",
BinOp::Rem(_) => "checked_rem",
BinOp::Shl(_) => "checked_shl",
BinOp::Shr(_) => "checked_shr",
_ => {
return quote! {
(#expr)
}
}
};
let fn_ident = TokenTree::Ident(Ident::new(function_name, Span::call_site()));
let left = crate::expr(&expr.left);
let right = crate::expr(&expr.right);
quote! {
#left.#fn_ident(#right)?
}
}
fn unary_expr(expr: &ExprUnary) -> TokenStream {
let function_name = match expr.op {
UnOp::Neg(_) => "checked_neg",
_ => {
return quote! {
(#expr)
}
}
};
let fn_ident = TokenTree::Ident(Ident::new(function_name, Span::call_site()));
let inner = crate::expr(&expr.expr);
quote! {
#inner.#fn_ident()?
}
}
fn method_call(expr: &ExprMethodCall) -> TokenStream {
let method_name = match expr.method.to_string().as_str() {
"abs" => "checked_abs",
"pow" => "checked_pow",
_ => {
return quote! {
(#expr)
}
}
};
let method_ident = TokenTree::Ident(Ident::new(method_name, Span::call_site()));
let left = crate::expr(&expr.receiver);
let args = &expr.args;
quote! {
#left.#method_ident(#args)?
}
}