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avoid-unnecessary-negations

Group: Style
Path: lint/style/avoid-unnecessary-negations
Default: Off, opt in
Origin: Falcon
Rule: 168 of 512

Simplifies negated bool literals and equality comparisons with a logical negation on both sides. Stacked negations belong to avoid-inverted-boolean-expressions; arithmetic, bitwise and relational operators are deliberately excluded.

Invalid

example.dartdart

bool trueLiteral() => !true;
bool falseLiteral() => !(false);
bool equal(bool flag, bool another) => !flag == !another;
bool unequal(bool flag, bool another) => (!flag) != (!another);
bool nested(bool a) => a && !true;
bool groupedEqual(bool a, bool b) => (!(a)) == (!(b));

Simplify these unnecessary logical negations.

1bool trueLiteral() => !true;

∙

Simplify these unnecessary logical negations.

1bool trueLiteral() => !true;

2bool falseLiteral() => !(false);

∙

Simplify these unnecessary logical negations.

2bool falseLiteral() => !(false);

3bool equal(bool flag, bool another) => !flag == !another;

∙

Simplify these unnecessary logical negations.

3bool equal(bool flag, bool another) => !flag == !another;

4bool unequal(bool flag, bool another) => (!flag) != (!another);

∙

Simplify these unnecessary logical negations.

4bool unequal(bool flag, bool another) => (!flag) != (!another);

5bool nested(bool a) => a && !true;

∙

Simplify these unnecessary logical negations.

5bool nested(bool a) => a && !true;

6bool groupedEqual(bool a, bool b) => (!(a)) == (!(b));

∙

Valid

example.dartdart

bool single(bool flag) => !flag;
bool equality(bool flag, bool another) => flag == another;
bool unequal(bool flag, bool another) => flag != another;
bool different(bool flag, bool another) => !flag == another;
bool conjunction(bool flag, bool another) => !flag && !another;
bool disjunction(bool flag, bool another) => !flag || !another;
int arithmetic(int value) => -(-value);
int bitwise(int value) => ~(~value);
bool relational(int a, int b) => !(a < b);
bool floating(double a, double b) => !(a >= b);
bool doubleNegation(bool flag) => !!flag;
bool parenthesized(bool flag) => !(!flag);
bool triple(bool flag) => !!!flag;
bool nested(bool a, bool b) => !!(a && !(!b));
bool stackedLiteral() => !!true;

Configure avoid-unnecessary-negations

Set its severity in falcon.json. See the configuration guide.

falcon.jsonjson

{
  "linter": {
    "rules": {
      "style": {
        "avoid-unnecessary-negations": "error"
      }
    }
  }
}

Or silence one occurrence with a suppression comment; the reason is required.

example.dartdart

// falcon-ignore lint/style/avoid-unnecessary-negations: <reason>

avoid-unnecessary-overrides-in-stateflutter
Redundant Flutter State overrides that drop inherited @protected.
avoid-unnecessary-reassignment
Reports an eager local initializer immediately overwritten without a read.
avoid-unnecessary-return
Flags bare returns at the end of a function or its final if/block branches.
avoid-unnecessary-super
Omit implicit super() initializers and provably redundant member prefixes.
avoid-unused-constructor-parametersavoid_unused_constructor_parameters
Flags constructor parameters that are never used.
avoid-void-asyncavoid_void_asyncrecommended
Avoid async functions and methods declared to return void.
avoid-wrapping-in-paddingflutter
Flags Padding directly wrapping a Flutter Container that can own the padding.
binary-expression-operand-orderbinary-expression-operand-order
Flags comparison expressions with a literal on the left-hand side.