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When suggesting from(x) for lossless casts, strip parens from x.

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This commit is contained in:
Dan Gohman 2017-08-30 16:06:21 -07:00
parent bc602df324
commit 35cf2715dc
3 changed files with 72 additions and 51 deletions
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17
clippy_lints/src/types.rs
View File

@ -10,7 +10,7 @@
use syntax::attr::IntType;
use syntax::codemap::Span;
use utils::{comparisons, higher, in_external_macro, in_macro, last_path_segment, match_def_path, match_path,
opt_def_id, snippet, span_help_and_lint, span_lint, span_lint_and_sugg, type_size};
opt_def_id, snippet, snippet_opt, span_help_and_lint, span_lint, span_lint_and_sugg, type_size};
use utils::paths;
/// Handles all the linting of funky types
@ -581,13 +581,26 @@ fn span_precision_loss_lint(cx: &LateContext, expr: &Expr, cast_from: Ty, cast_t
}
fn span_lossless_lint(cx: &LateContext, expr: &Expr, op: &Expr, cast_from: Ty, cast_to: Ty) {
// The suggestion is to use a function call, so if the original expression
// has parens on the outside, they are no longer needed.
let opt = snippet_opt(cx, op.span);
let sugg = if let Some(ref snip) = opt {
if snip.starts_with('(') && snip.ends_with(')') {
&snip[1..snip.len()-1]
} else {
snip.as_str()
}
} else {
".."
};
span_lint_and_sugg(
cx,
CAST_LOSSLESS,
expr.span,
&format!("casting {} to {} may become silently lossy if types change", cast_from, cast_to),
"try",
format!("{}::from({})", cast_to, &snippet(cx, op.span, "..")),
format!("{}::from({})", cast_to, sugg),
);
}

2
tests/ui/cast.rs
View File

@ -57,6 +57,8 @@ fn main() {
1u32 as f64;
// Test cast_lossless with casts from floating-point types
1.0f32 as f64;
// Test cast_lossless with an expression wrapped in parens
(1u8 + 1u8) as u16;
// Test cast_sign_loss
1i32 as u32;
1isize as usize;

104
tests/ui/cast.stderr
View File

@ -308,151 +308,157 @@ error: casting f32 to f64 may become silently lossy if types change
59 | 1.0f32 as f64;
| ^^^^^^^^^^^^^ help: try: `f64::from(1.0f32)`
error: casting i32 to u32 may lose the sign of the value
error: casting u8 to u16 may become silently lossy if types change
--> $DIR/cast.rs:61:5
|
61 | 1i32 as u32;
61 | (1u8 + 1u8) as u16;
| ^^^^^^^^^^^^^^^^^^ help: try: `u16::from(1u8 + 1u8)`
error: casting i32 to u32 may lose the sign of the value
--> $DIR/cast.rs:63:5
|
63 | 1i32 as u32;
| ^^^^^^^^^^^
error: casting isize to usize may lose the sign of the value
--> $DIR/cast.rs:62:5
--> $DIR/cast.rs:64:5
|
62 | 1isize as usize;
64 | 1isize as usize;
| ^^^^^^^^^^^^^^^
error: casting isize to i8 may truncate the value
--> $DIR/cast.rs:65:5
--> $DIR/cast.rs:67:5
|
65 | 1isize as i8;
67 | 1isize as i8;
| ^^^^^^^^^^^^
error: casting isize to f64 causes a loss of precision on targets with 64-bit wide pointers (isize is 64 bits wide, but f64's mantissa is only 52 bits wide)
--> $DIR/cast.rs:66:5
--> $DIR/cast.rs:68:5
|
66 | 1isize as f64;
68 | 1isize as f64;
| ^^^^^^^^^^^^^
error: casting usize to f64 causes a loss of precision on targets with 64-bit wide pointers (usize is 64 bits wide, but f64's mantissa is only 52 bits wide)
--> $DIR/cast.rs:67:5
--> $DIR/cast.rs:69:5
|
67 | 1usize as f64;
69 | 1usize as f64;
| ^^^^^^^^^^^^^
error: casting isize to f32 causes a loss of precision (isize is 32 or 64 bits wide, but f32's mantissa is only 23 bits wide)
--> $DIR/cast.rs:68:5
--> $DIR/cast.rs:70:5
|
68 | 1isize as f32;
70 | 1isize as f32;
| ^^^^^^^^^^^^^
error: casting usize to f32 causes a loss of precision (usize is 32 or 64 bits wide, but f32's mantissa is only 23 bits wide)
--> $DIR/cast.rs:69:5
--> $DIR/cast.rs:71:5
|
69 | 1usize as f32;
71 | 1usize as f32;
| ^^^^^^^^^^^^^
error: casting isize to i32 may truncate the value on targets with 64-bit wide pointers
--> $DIR/cast.rs:70:5
--> $DIR/cast.rs:72:5
|
70 | 1isize as i32;
72 | 1isize as i32;
| ^^^^^^^^^^^^^
error: casting isize to u32 may lose the sign of the value
--> $DIR/cast.rs:71:5
--> $DIR/cast.rs:73:5
|
71 | 1isize as u32;
73 | 1isize as u32;
| ^^^^^^^^^^^^^
error: casting isize to u32 may truncate the value on targets with 64-bit wide pointers
--> $DIR/cast.rs:71:5
--> $DIR/cast.rs:73:5
|
71 | 1isize as u32;
73 | 1isize as u32;
| ^^^^^^^^^^^^^
error: casting usize to u32 may truncate the value on targets with 64-bit wide pointers
--> $DIR/cast.rs:72:5
--> $DIR/cast.rs:74:5
|
72 | 1usize as u32;
74 | 1usize as u32;
| ^^^^^^^^^^^^^
error: casting usize to i32 may truncate the value on targets with 64-bit wide pointers
--> $DIR/cast.rs:73:5
--> $DIR/cast.rs:75:5
|
73 | 1usize as i32;
75 | 1usize as i32;
| ^^^^^^^^^^^^^
error: casting usize to i32 may wrap around the value on targets with 32-bit wide pointers
--> $DIR/cast.rs:73:5
--> $DIR/cast.rs:75:5
|
73 | 1usize as i32;
75 | 1usize as i32;
| ^^^^^^^^^^^^^
error: casting i64 to isize may truncate the value on targets with 32-bit wide pointers
--> $DIR/cast.rs:75:5
--> $DIR/cast.rs:77:5
|
75 | 1i64 as isize;
77 | 1i64 as isize;
| ^^^^^^^^^^^^^
error: casting i64 to usize may lose the sign of the value
--> $DIR/cast.rs:76:5
--> $DIR/cast.rs:78:5
|
76 | 1i64 as usize;
78 | 1i64 as usize;
| ^^^^^^^^^^^^^
error: casting i64 to usize may truncate the value on targets with 32-bit wide pointers
--> $DIR/cast.rs:76:5
--> $DIR/cast.rs:78:5
|
76 | 1i64 as usize;
78 | 1i64 as usize;
| ^^^^^^^^^^^^^
error: casting u64 to isize may truncate the value on targets with 32-bit wide pointers
--> $DIR/cast.rs:77:5
--> $DIR/cast.rs:79:5
|
77 | 1u64 as isize;
79 | 1u64 as isize;
| ^^^^^^^^^^^^^
error: casting u64 to isize may wrap around the value on targets with 64-bit wide pointers
--> $DIR/cast.rs:77:5
--> $DIR/cast.rs:79:5
|
77 | 1u64 as isize;
79 | 1u64 as isize;
| ^^^^^^^^^^^^^
error: casting u64 to usize may truncate the value on targets with 32-bit wide pointers
--> $DIR/cast.rs:78:5
--> $DIR/cast.rs:80:5
|
78 | 1u64 as usize;
80 | 1u64 as usize;
| ^^^^^^^^^^^^^
error: casting u32 to isize may wrap around the value on targets with 32-bit wide pointers
--> $DIR/cast.rs:79:5
--> $DIR/cast.rs:81:5
|
79 | 1u32 as isize;
81 | 1u32 as isize;
| ^^^^^^^^^^^^^
error: casting i32 to usize may lose the sign of the value
--> $DIR/cast.rs:82:5
--> $DIR/cast.rs:84:5
|
82 | 1i32 as usize;
84 | 1i32 as usize;
| ^^^^^^^^^^^^^
error: casting to the same type is unnecessary (`i32` -> `i32`)
--> $DIR/cast.rs:84:5
--> $DIR/cast.rs:86:5
|
84 | 1i32 as i32;
86 | 1i32 as i32;
| ^^^^^^^^^^^
|
= note: `-D unnecessary-cast` implied by `-D warnings`
error: casting to the same type is unnecessary (`f32` -> `f32`)
--> $DIR/cast.rs:85:5
--> $DIR/cast.rs:87:5
|
85 | 1f32 as f32;
87 | 1f32 as f32;
| ^^^^^^^^^^^
error: casting to the same type is unnecessary (`bool` -> `bool`)
--> $DIR/cast.rs:86:5
--> $DIR/cast.rs:88:5
|
86 | false as bool;
88 | false as bool;
| ^^^^^^^^^^^^^
error: aborting due to 74 previous errors
error: aborting due to 75 previous errors