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
use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
use rustc::hir::*;
use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
use utils::*;
declare_lint! {
pub BLOCK_IN_IF_CONDITION_EXPR,
Warn,
"braces that can be eliminated in conditions, e.g. `if { true } ...`"
}
declare_lint! {
pub BLOCK_IN_IF_CONDITION_STMT,
Warn,
"complex blocks in conditions, e.g. `if { let x = true; x } ...`"
}
#[derive(Copy, Clone)]
pub struct BlockInIfCondition;
impl LintPass for BlockInIfCondition {
fn get_lints(&self) -> LintArray {
lint_array!(BLOCK_IN_IF_CONDITION_EXPR, BLOCK_IN_IF_CONDITION_STMT)
}
}
struct ExVisitor<'a, 'tcx: 'a> {
found_block: Option<&'tcx Expr>,
cx: &'a LateContext<'a, 'tcx>,
}
impl<'a, 'tcx: 'a> Visitor<'tcx> for ExVisitor<'a, 'tcx> {
fn visit_expr(&mut self, expr: &'tcx Expr) {
if let ExprClosure(_, _, eid, _, _) = expr.node {
let body = self.cx.tcx.hir.body(eid);
let ex = &body.value;
if matches!(ex.node, ExprBlock(_)) {
self.found_block = Some(ex);
return;
}
}
walk_expr(self, expr);
}
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::None
}
}
const BRACED_EXPR_MESSAGE: &str = "omit braces around single expression condition";
const COMPLEX_BLOCK_MESSAGE: &str = "in an 'if' condition, avoid complex blocks or closures with blocks; \
instead, move the block or closure higher and bind it with a 'let'";
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BlockInIfCondition {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
if let ExprIf(ref check, ref then, _) = expr.node {
if let ExprBlock(ref block) = check.node {
if block.rules == DefaultBlock {
if block.stmts.is_empty() {
if let Some(ref ex) = block.expr {
if in_macro(expr.span) || differing_macro_contexts(expr.span, ex.span) {
return;
}
span_help_and_lint(
cx,
BLOCK_IN_IF_CONDITION_EXPR,
check.span,
BRACED_EXPR_MESSAGE,
&format!(
"try\nif {} {} ... ",
snippet_block(cx, ex.span, ".."),
snippet_block(cx, then.span, "..")
),
);
}
} else {
let span = block
.expr
.as_ref()
.map_or_else(|| block.stmts[0].span, |e| e.span);
if in_macro(span) || differing_macro_contexts(expr.span, span) {
return;
}
span_help_and_lint(
cx,
BLOCK_IN_IF_CONDITION_STMT,
check.span,
COMPLEX_BLOCK_MESSAGE,
&format!(
"try\nlet res = {};\nif res {} ... ",
snippet_block(cx, block.span, ".."),
snippet_block(cx, then.span, "..")
),
);
}
}
} else {
let mut visitor = ExVisitor {
found_block: None,
cx: cx,
};
walk_expr(&mut visitor, check);
if let Some(block) = visitor.found_block {
span_lint(cx, BLOCK_IN_IF_CONDITION_STMT, block.span, COMPLEX_BLOCK_MESSAGE);
}
}
}
}
}