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pmk21pmk21
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Added final lint and tests
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4 files changed

+660
-44
lines changed

4 files changed

+660
-44
lines changed

‎clippy_lints/src/implicit_saturating_sub.rs

+117-34
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,4 @@
1-
use crate::utils::{higher, in_macro, span_lint_and_sugg};
1+
use crate::utils::{higher, in_macro, match_qpath, span_lint_and_sugg, SpanlessEq};
22
use if_chain::if_chain;
33
use rustc_ast::ast::LitKind;
44
use rustc_errors::Applicability;
@@ -9,17 +9,17 @@ use rustc_session::{declare_lint_pass, declare_tool_lint};
99
declare_clippy_lint! {
1010
/// **What it does:** Checks for implicit saturating subtraction.
1111
///
12-
/// **Why is this bad?** Simplicity and readability. Instead we can easily use an inbuilt function.
12+
/// **Why is this bad?** Simplicity and readability. Instead we can easily use an builtin function.
1313
///
1414
/// **Known problems:** None.
1515
///
1616
/// **Example:**
1717
///
1818
/// ```rust
19-
/// let end = 10;
20-
/// let start = 5;
19+
/// let end: u32 = 10;
20+
/// let start: u32 = 5;
2121
///
22-
/// let mut i = end - start;
22+
/// let mut i: u32 = end - start;
2323
///
2424
/// // Bad
2525
/// if i != 0 {
@@ -28,13 +28,13 @@ declare_clippy_lint! {
2828
/// ```
2929
/// Use instead:
3030
/// ```rust
31-
/// let end = 10;
32-
/// let start = 5;
31+
/// let end: u32 = 10;
32+
/// let start: u32 = 5;
3333
///
34-
/// let mut i = end - start;
34+
/// let mut i: u32 = end - start;
3535
///
3636
/// // Good
37-
/// i.saturating_sub(1);
37+
/// i = i.saturating_sub(1);
3838
/// ```
3939
pub IMPLICIT_SATURATING_SUB,
4040
pedantic,
@@ -50,41 +50,124 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitSaturatingSub {
5050
}
5151
if_chain! {
5252
if let Some((ref cond, ref then, None)) = higher::if_block(&expr);
53+
5354
// Check if the conditional expression is a binary operation
54-
if let ExprKind::Binary(ref op, ref left, ref right) = cond.kind;
55-
// Ensure that the binary operator is > or !=
56-
if BinOpKind::Ne == op.node || BinOpKind::Gt == op.node;
57-
if let ExprKind::Path(ref cond_path) = left.kind;
58-
// Get the literal on the right hand side
59-
if let ExprKind::Lit(ref lit) = right.kind;
60-
if let LitKind::Int(0, _) = lit.node;
55+
if let ExprKind::Binary(ref cond_op, ref cond_left, ref cond_right) = cond.kind;
56+
57+
// Ensure that the binary operator is >, != and <
58+
if BinOpKind::Ne == cond_op.node || BinOpKind::Gt == cond_op.node || BinOpKind::Lt == cond_op.node;
59+
6160
// Check if the true condition block has only one statement
6261
if let ExprKind::Block(ref block, _) = then.kind;
63-
if block.stmts.len() == 1;
62+
if block.stmts.len() == 1 && block.expr.is_none();
63+
6464
// Check if assign operation is done
6565
if let StmtKind::Semi(ref e) = block.stmts[0].kind;
66-
if let ExprKind::AssignOp(ref op1, ref target, ref value) = e.kind;
67-
if BinOpKind::Sub == op1.node;
66+
if let Some(target) = subtracts_one(cx, e);
67+
68+
// Extracting out the variable name
6869
if let ExprKind::Path(ref assign_path) = target.kind;
69-
// Check if the variable in the condition and assignment statement are the same
70-
if let (QPath::Resolved(_, ref cres_path), QPath::Resolved(_, ref ares_path)) = (cond_path, assign_path);
71-
if cres_path.res == ares_path.res;
72-
if let ExprKind::Lit(ref lit1) = value.kind;
73-
if let LitKind::Int(assign_lit, _) = lit1.node;
70+
if let QPath::Resolved(_, ref ares_path) = assign_path;
71+
7472
then {
73+
// Handle symmetric conditions in the if statement
74+
let (cond_var, cond_num_val) = if SpanlessEq::new(cx).eq_expr(cond_left, target) {
75+
if BinOpKind::Gt == cond_op.node || BinOpKind::Ne == cond_op.node {
76+
(cond_left, cond_right)
77+
} else {
78+
return;
79+
}
80+
} else if SpanlessEq::new(cx).eq_expr(cond_right, target) {
81+
if BinOpKind::Lt == cond_op.node || BinOpKind::Ne == cond_op.node {
82+
(cond_right, cond_left)
83+
} else {
84+
return;
85+
}
86+
} else {
87+
return;
88+
};
89+
90+
// Check if the variable in the condition statement is an integer
91+
if !cx.tables.expr_ty(cond_var).is_integral() {
92+
return;
93+
}
94+
7595
// Get the variable name
7696
let var_name = ares_path.segments[0].ident.name.as_str();
77-
let applicability = Applicability::MaybeIncorrect;
78-
span_lint_and_sugg(
79-
cx,
80-
IMPLICIT_SATURATING_SUB,
81-
expr.span,
82-
"Implicitly performing saturating subtraction",
83-
"try",
84-
format!("{}.saturating_sub({});", var_name, assign_lit.to_string()),
85-
applicability
86-
);
97+
const INT_TYPES: [&str; 5] = ["i8", "i16", "i32", "i64", "i128"];
98+
99+
match cond_num_val.kind {
100+
ExprKind::Lit(ref cond_lit) => {
101+
// Check if the constant is zero
102+
if let LitKind::Int(0, _) = cond_lit.node {
103+
if cx.tables.expr_ty(cond_left).is_signed() {
104+
} else {
105+
print_lint_and_sugg(cx, &var_name, expr);
106+
};
107+
}
108+
},
109+
ExprKind::Path(ref cond_num_path) => {
110+
if INT_TYPES.iter().any(|int_type| match_qpath(cond_num_path, &[int_type, "MIN"])) {
111+
print_lint_and_sugg(cx, &var_name, expr);
112+
};
113+
},
114+
ExprKind::Call(ref func, _) => {
115+
if let ExprKind::Path(ref cond_num_path) = func.kind {
116+
if INT_TYPES.iter().any(|int_type| match_qpath(cond_num_path, &[int_type, "min_value"])) {
117+
print_lint_and_sugg(cx, &var_name, expr);
118+
}
119+
};
120+
},
121+
_ => (),
122+
}
87123
}
88124
}
89125
}
90126
}
127+
128+
fn subtracts_one<'a>(cx: &LateContext<'_, '_>, expr: &Expr<'a>) -> Option<&'a Expr<'a>> {
129+
match expr.kind {
130+
ExprKind::AssignOp(ref op1, ref target, ref value) => {
131+
if_chain! {
132+
if BinOpKind::Sub == op1.node;
133+
// Check if literal being subtracted is one
134+
if let ExprKind::Lit(ref lit1) = value.kind;
135+
if let LitKind::Int(1, _) = lit1.node;
136+
then {
137+
Some(target)
138+
} else {
139+
None
140+
}
141+
}
142+
},
143+
ExprKind::Assign(ref target, ref value, _) => {
144+
if_chain! {
145+
if let ExprKind::Binary(ref op1, ref left1, ref right1) = value.kind;
146+
if BinOpKind::Sub == op1.node;
147+
148+
if SpanlessEq::new(cx).eq_expr(left1, target);
149+
150+
if let ExprKind::Lit(ref lit1) = right1.kind;
151+
if let LitKind::Int(1, _) = lit1.node;
152+
then {
153+
Some(target)
154+
} else {
155+
None
156+
}
157+
}
158+
},
159+
_ => None,
160+
}
161+
}
162+
163+
fn print_lint_and_sugg(cx: &LateContext<'_, '_>, var_name: &str, expr: &Expr<'_>) {
164+
span_lint_and_sugg(
165+
cx,
166+
IMPLICIT_SATURATING_SUB,
167+
expr.span,
168+
"Implicitly performing saturating subtraction",
169+
"try",
170+
format!("{} = {}.saturating_sub({});", var_name, var_name, 1.to_string()),
171+
Applicability::MachineApplicable,
172+
);
173+
}

‎tests/ui/implicit_saturating_sub.fixed

+160
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,160 @@
1+
// run-rustfix
2+
#![allow(unused_assignments, unused_mut)]
3+
#![warn(clippy::implicit_saturating_sub)]
4+
5+
fn main() {
6+
// Tests for unsigned integers
7+
8+
let end_8: u8 = 10;
9+
let start_8: u8 = 5;
10+
let mut u_8: u8 = end_8 - start_8;
11+
12+
// Lint
13+
u_8 = u_8.saturating_sub(1);
14+
15+
match end_8 {
16+
10 => {
17+
// Lint
18+
u_8 = u_8.saturating_sub(1);
19+
},
20+
11 => u_8 += 1,
21+
_ => u_8 = 0,
22+
}
23+
24+
let end_16: u16 = 35;
25+
let start_16: u16 = 40;
26+
27+
let mut u_16: u16 = end_16 - start_16;
28+
29+
// Lint
30+
u_16 = u_16.saturating_sub(1);
31+
32+
let mut end_32: u32 = 7000;
33+
let mut start_32: u32 = 7010;
34+
35+
let mut u_32: u32 = end_32 - start_32;
36+
37+
// Lint
38+
u_32 = u_32.saturating_sub(1);
39+
40+
// No Lint
41+
if u_32 > 0 {
42+
u_16 += 1;
43+
}
44+
45+
// No Lint
46+
if u_32 != 0 {
47+
end_32 -= 1;
48+
start_32 += 1;
49+
}
50+
51+
let mut end_64: u64 = 75001;
52+
let mut start_64: u64 = 75000;
53+
54+
let mut u_64: u64 = end_64 - start_64;
55+
56+
// Lint
57+
u_64 = u_64.saturating_sub(1);
58+
59+
// Lint
60+
u_64 = u_64.saturating_sub(1);
61+
62+
// Lint
63+
u_64 = u_64.saturating_sub(1);
64+
65+
// No Lint
66+
if u_64 >= 1 {
67+
u_64 -= 1;
68+
}
69+
70+
// No Lint
71+
if u_64 > 0 {
72+
end_64 -= 1;
73+
}
74+
75+
// Tests for usize
76+
let end_usize: usize = 8054;
77+
let start_usize: usize = 8050;
78+
79+
let mut u_usize: usize = end_usize - start_usize;
80+
81+
// Lint
82+
u_usize = u_usize.saturating_sub(1);
83+
84+
// Tests for signed integers
85+
86+
let endi_8: i8 = 10;
87+
let starti_8: i8 = 50;
88+
89+
let mut i_8: i8 = endi_8 - starti_8;
90+
91+
// Lint
92+
i_8 = i_8.saturating_sub(1);
93+
94+
// Lint
95+
i_8 = i_8.saturating_sub(1);
96+
97+
// Lint
98+
i_8 = i_8.saturating_sub(1);
99+
100+
// Lint
101+
i_8 = i_8.saturating_sub(1);
102+
103+
let endi_16: i16 = 45;
104+
let starti_16: i16 = 44;
105+
106+
let mut i_16: i16 = endi_16 - starti_16;
107+
108+
// Lint
109+
i_16 = i_16.saturating_sub(1);
110+
111+
// Lint
112+
i_16 = i_16.saturating_sub(1);
113+
114+
// Lint
115+
i_16 = i_16.saturating_sub(1);
116+
117+
// Lint
118+
i_16 = i_16.saturating_sub(1);
119+
120+
let endi_32: i32 = 45;
121+
let starti_32: i32 = 44;
122+
123+
let mut i_32: i32 = endi_32 - starti_32;
124+
125+
// Lint
126+
i_32 = i_32.saturating_sub(1);
127+
128+
// Lint
129+
i_32 = i_32.saturating_sub(1);
130+
131+
// Lint
132+
i_32 = i_32.saturating_sub(1);
133+
134+
// Lint
135+
i_32 = i_32.saturating_sub(1);
136+
137+
let endi_64: i64 = 45;
138+
let starti_64: i64 = 44;
139+
140+
let mut i_64: i64 = endi_64 - starti_64;
141+
142+
// Lint
143+
i_64 = i_64.saturating_sub(1);
144+
145+
// Lint
146+
i_64 = i_64.saturating_sub(1);
147+
148+
// Lint
149+
i_64 = i_64.saturating_sub(1);
150+
151+
// No Lint
152+
if i_64 > 0 {
153+
i_64 -= 1;
154+
}
155+
156+
// No Lint
157+
if i_64 != 0 {
158+
i_64 -= 1;
159+
}
160+
}

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