Update unnecessary_operation and no_effect to not suggest removing

structs/enums wrappers when that type implements Drop as noted
in #2061.
This commit is contained in:
Chris Emerson 2017-09-18 20:07:33 +01:00
parent 2bb8efdb4d
commit f680eb164d
3 changed files with 259 additions and 209 deletions

View file

@ -40,12 +40,22 @@ declare_lint! {
"outer expressions with no effect"
}
/// Check whether this type implements Drop.
fn has_drop(cx: &LateContext, expr: &Expr) -> bool {
let struct_ty = cx.tables.expr_ty(expr);
match struct_ty.ty_adt_def() {
Some(def) => def.has_dtor(cx.tcx),
_ => false,
}
}
fn has_no_effect(cx: &LateContext, expr: &Expr) -> bool {
if in_macro(expr.span) {
return false;
}
match expr.node {
Expr_::ExprLit(..) | Expr_::ExprClosure(.., _) | Expr_::ExprPath(..) => true,
Expr_::ExprLit(..) | Expr_::ExprClosure(.., _) => true,
Expr_::ExprPath(..) => !has_drop(cx, expr),
Expr_::ExprIndex(ref a, ref b) | Expr_::ExprBinary(_, ref a, ref b) => {
has_no_effect(cx, a) && has_no_effect(cx, b)
},
@ -59,7 +69,7 @@ fn has_no_effect(cx: &LateContext, expr: &Expr) -> bool {
Expr_::ExprAddrOf(_, ref inner) |
Expr_::ExprBox(ref inner) => has_no_effect(cx, inner),
Expr_::ExprStruct(_, ref fields, ref base) => {
fields.iter().all(|field| has_no_effect(cx, &field.expr)) && match *base {
!has_drop(cx, expr) && fields.iter().all(|field| has_no_effect(cx, &field.expr)) && match *base {
Some(ref base) => has_no_effect(cx, base),
None => true,
}
@ -68,7 +78,7 @@ fn has_no_effect(cx: &LateContext, expr: &Expr) -> bool {
let def = cx.tables.qpath_def(qpath, callee.hir_id);
match def {
Def::Struct(..) | Def::Variant(..) | Def::StructCtor(..) | Def::VariantCtor(..) => {
args.iter().all(|arg| has_no_effect(cx, arg))
!has_drop(cx, expr) && args.iter().all(|arg| has_no_effect(cx, arg))
},
_ => false,
}
@ -145,18 +155,23 @@ fn reduce_expression<'a>(cx: &LateContext, expr: &'a Expr) -> Option<Vec<&'a Exp
Expr_::ExprTupField(ref inner, _) |
Expr_::ExprAddrOf(_, ref inner) |
Expr_::ExprBox(ref inner) => reduce_expression(cx, inner).or_else(|| Some(vec![inner])),
Expr_::ExprStruct(_, ref fields, ref base) => Some(
fields
.iter()
.map(|f| &f.expr)
.chain(base)
.map(Deref::deref)
.collect(),
),
Expr_::ExprStruct(_, ref fields, ref base) => {
if has_drop(cx, expr) {
None
} else {
Some(
fields
.iter()
.map(|f| &f.expr)
.chain(base)
.map(Deref::deref)
.collect())
}
},
Expr_::ExprCall(ref callee, ref args) => if let Expr_::ExprPath(ref qpath) = callee.node {
let def = cx.tables.qpath_def(qpath, callee.hir_id);
match def {
Def::Struct(..) | Def::Variant(..) | Def::StructCtor(..) | Def::VariantCtor(..) => {
Def::Struct(..) | Def::Variant(..) | Def::StructCtor(..) | Def::VariantCtor(..) if !has_drop(cx, expr) => {
Some(args.iter().collect())
},
_ => None,

View file

@ -16,6 +16,27 @@ enum Enum {
Tuple(i32),
Struct { field: i32 },
}
struct DropUnit;
impl Drop for DropUnit {
fn drop(&mut self) {}
}
struct DropStruct {
field: i32
}
impl Drop for DropStruct {
fn drop(&mut self) {}
}
struct DropTuple(i32);
impl Drop for DropTuple {
fn drop(&mut self) {}
}
enum DropEnum {
Tuple(i32),
Struct { field: i32 },
}
impl Drop for DropEnum {
fn drop(&mut self) {}
}
union Union {
a: u8,
@ -24,6 +45,7 @@ union Union {
fn get_number() -> i32 { 0 }
fn get_struct() -> Struct { Struct { field: 0 } }
fn get_drop_struct() -> DropStruct { DropStruct { field: 0 } }
unsafe fn unsafe_fn() -> i32 { 0 }
@ -61,6 +83,11 @@ fn main() {
// Do not warn
get_number();
unsafe { unsafe_fn() };
DropUnit;
DropStruct { field: 0 };
DropTuple(0);
DropEnum::Tuple(0);
DropEnum::Struct { field: 0 };
Tuple(get_number());
Struct { field: get_number() };
@ -81,4 +108,12 @@ fn main() {
[get_number(); 55];
[42; 55][get_number() as usize];
{get_number()};
// Do not warn
DropTuple(get_number());
DropStruct { field: get_number() };
DropStruct { field: get_number() };
DropStruct { ..get_drop_struct() };
DropEnum::Tuple(get_number());
DropEnum::Struct { field: get_number() };
}

View file

@ -1,270 +1,270 @@
error: statement with no effect
--> $DIR/no_effect.rs:34:5
--> $DIR/no_effect.rs:56:5
|
34 | 0;
56 | 0;
| ^^
|
= note: `-D no-effect` implied by `-D warnings`
error: statement with no effect
--> $DIR/no_effect.rs:35:5
|
35 | s2;
| ^^^
error: statement with no effect
--> $DIR/no_effect.rs:36:5
|
36 | Unit;
| ^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:37:5
|
37 | Tuple(0);
| ^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:38:5
|
38 | Struct { field: 0 };
| ^^^^^^^^^^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:39:5
|
39 | Struct { ..s };
| ^^^^^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:40:5
|
40 | Union { a: 0 };
| ^^^^^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:41:5
|
41 | Enum::Tuple(0);
| ^^^^^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:42:5
|
42 | Enum::Struct { field: 0 };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:43:5
|
43 | 5 + 6;
| ^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:44:5
|
44 | *&42;
| ^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:45:5
|
45 | &6;
| ^^^
error: statement with no effect
--> $DIR/no_effect.rs:46:5
|
46 | (5, 6, 7);
| ^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:47:5
|
47 | box 42;
| ^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:48:5
|
48 | ..;
| ^^^
error: statement with no effect
--> $DIR/no_effect.rs:49:5
|
49 | 5..;
| ^^^^
error: statement with no effect
--> $DIR/no_effect.rs:50:5
|
50 | ..5;
| ^^^^
error: statement with no effect
--> $DIR/no_effect.rs:51:5
|
51 | 5..6;
| ^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:52:5
|
52 | 5...6;
| ^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:53:5
|
53 | [42, 55];
| ^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:54:5
|
54 | [42, 55][1];
| ^^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:55:5
|
55 | (42, 55).1;
| ^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:56:5
|
56 | [42; 55];
| ^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:57:5
|
57 | [42; 55][13];
| ^^^^^^^^^^^^^
57 | s2;
| ^^^
error: statement with no effect
--> $DIR/no_effect.rs:58:5
|
58 | Unit;
| ^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:59:5
|
59 | || x += 5;
59 | Tuple(0);
| ^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:60:5
|
60 | Struct { field: 0 };
| ^^^^^^^^^^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:61:5
|
61 | Struct { ..s };
| ^^^^^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:62:5
|
62 | Union { a: 0 };
| ^^^^^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:63:5
|
63 | Enum::Tuple(0);
| ^^^^^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:64:5
|
64 | Enum::Struct { field: 0 };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:65:5
|
65 | 5 + 6;
| ^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:66:5
|
66 | *&42;
| ^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:67:5
|
67 | &6;
| ^^^
error: statement with no effect
--> $DIR/no_effect.rs:68:5
|
68 | (5, 6, 7);
| ^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:69:5
|
69 | box 42;
| ^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:70:5
|
70 | ..;
| ^^^
error: statement with no effect
--> $DIR/no_effect.rs:71:5
|
71 | 5..;
| ^^^^
error: statement with no effect
--> $DIR/no_effect.rs:72:5
|
72 | ..5;
| ^^^^
error: statement with no effect
--> $DIR/no_effect.rs:73:5
|
73 | 5..6;
| ^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:74:5
|
74 | 5...6;
| ^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:75:5
|
75 | [42, 55];
| ^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:76:5
|
76 | [42, 55][1];
| ^^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:77:5
|
77 | (42, 55).1;
| ^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:78:5
|
78 | [42; 55];
| ^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:79:5
|
79 | [42; 55][13];
| ^^^^^^^^^^^^^
error: statement with no effect
--> $DIR/no_effect.rs:81:5
|
81 | || x += 5;
| ^^^^^^^^^^
error: statement can be reduced
--> $DIR/no_effect.rs:65:5
--> $DIR/no_effect.rs:92:5
|
65 | Tuple(get_number());
92 | Tuple(get_number());
| ^^^^^^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
|
= note: `-D unnecessary-operation` implied by `-D warnings`
error: statement can be reduced
--> $DIR/no_effect.rs:66:5
--> $DIR/no_effect.rs:93:5
|
66 | Struct { field: get_number() };
93 | Struct { field: get_number() };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
error: statement can be reduced
--> $DIR/no_effect.rs:67:5
--> $DIR/no_effect.rs:94:5
|
67 | Struct { ..get_struct() };
94 | Struct { ..get_struct() };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `get_struct();`
error: statement can be reduced
--> $DIR/no_effect.rs:68:5
--> $DIR/no_effect.rs:95:5
|
68 | Enum::Tuple(get_number());
95 | Enum::Tuple(get_number());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
error: statement can be reduced
--> $DIR/no_effect.rs:69:5
--> $DIR/no_effect.rs:96:5
|
69 | Enum::Struct { field: get_number() };
96 | Enum::Struct { field: get_number() };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
error: statement can be reduced
--> $DIR/no_effect.rs:70:5
--> $DIR/no_effect.rs:97:5
|
70 | 5 + get_number();
97 | 5 + get_number();
| ^^^^^^^^^^^^^^^^^ help: replace it with: `5;get_number();`
error: statement can be reduced
--> $DIR/no_effect.rs:71:5
--> $DIR/no_effect.rs:98:5
|
71 | *&get_number();
98 | *&get_number();
| ^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
error: statement can be reduced
--> $DIR/no_effect.rs:72:5
--> $DIR/no_effect.rs:99:5
|
72 | &get_number();
99 | &get_number();
| ^^^^^^^^^^^^^^ help: replace it with: `get_number();`
error: statement can be reduced
--> $DIR/no_effect.rs:73:5
|
73 | (5, 6, get_number());
| ^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `5;6;get_number();`
--> $DIR/no_effect.rs:100:5
|
100 | (5, 6, get_number());
| ^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `5;6;get_number();`
error: statement can be reduced
--> $DIR/no_effect.rs:74:5
|
74 | box get_number();
| ^^^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
--> $DIR/no_effect.rs:101:5
|
101 | box get_number();
| ^^^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
error: statement can be reduced
--> $DIR/no_effect.rs:75:5
|
75 | get_number()..;
| ^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
--> $DIR/no_effect.rs:102:5
|
102 | get_number()..;
| ^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
error: statement can be reduced
--> $DIR/no_effect.rs:76:5
|
76 | ..get_number();
| ^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
--> $DIR/no_effect.rs:103:5
|
103 | ..get_number();
| ^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
error: statement can be reduced
--> $DIR/no_effect.rs:77:5
|
77 | 5..get_number();
| ^^^^^^^^^^^^^^^^ help: replace it with: `5;get_number();`
--> $DIR/no_effect.rs:104:5
|
104 | 5..get_number();
| ^^^^^^^^^^^^^^^^ help: replace it with: `5;get_number();`
error: statement can be reduced
--> $DIR/no_effect.rs:78:5
|
78 | [42, get_number()];
| ^^^^^^^^^^^^^^^^^^^ help: replace it with: `42;get_number();`
--> $DIR/no_effect.rs:105:5
|
105 | [42, get_number()];
| ^^^^^^^^^^^^^^^^^^^ help: replace it with: `42;get_number();`
error: statement can be reduced
--> $DIR/no_effect.rs:79:5
|
79 | [42, 55][get_number() as usize];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `[42, 55];get_number() as usize;`
--> $DIR/no_effect.rs:106:5
|
106 | [42, 55][get_number() as usize];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `[42, 55];get_number() as usize;`
error: statement can be reduced
--> $DIR/no_effect.rs:80:5
|
80 | (42, get_number()).1;
| ^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `42;get_number();`
--> $DIR/no_effect.rs:107:5
|
107 | (42, get_number()).1;
| ^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `42;get_number();`
error: statement can be reduced
--> $DIR/no_effect.rs:81:5
|
81 | [get_number(); 55];
| ^^^^^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
--> $DIR/no_effect.rs:108:5
|
108 | [get_number(); 55];
| ^^^^^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
error: statement can be reduced
--> $DIR/no_effect.rs:82:5
|
82 | [42; 55][get_number() as usize];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `[42; 55];get_number() as usize;`
--> $DIR/no_effect.rs:109:5
|
109 | [42; 55][get_number() as usize];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `[42; 55];get_number() as usize;`
error: statement can be reduced
--> $DIR/no_effect.rs:83:5
|
83 | {get_number()};
| ^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
--> $DIR/no_effect.rs:110:5
|
110 | {get_number()};
| ^^^^^^^^^^^^^^^ help: replace it with: `get_number();`
error: aborting due to 44 previous errors