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https://github.com/ethereum/solidity
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Restrict unary negation to signed integers.
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@ -1,5 +1,7 @@
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### 0.8.0 (unreleased)
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Breaking Changes:
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* Type System: Unary negation can only be used on signed integers, not on unsigned integers.
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### 0.7.2 (unreleased)
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@ -38,7 +38,7 @@ Operators:
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* Comparisons: ``<=``, ``<``, ``==``, ``!=``, ``>=``, ``>`` (evaluate to ``bool``)
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* Bit operators: ``&``, ``|``, ``^`` (bitwise exclusive or), ``~`` (bitwise negation)
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* Shift operators: ``<<`` (left shift), ``>>`` (right shift)
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* Arithmetic operators: ``+``, ``-``, unary ``-``, ``*``, ``/``, ``%`` (modulo), ``**`` (exponentiation)
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* Arithmetic operators: ``+``, ``-``, unary ``-`` (only for signed integers), ``*``, ``/``, ``%`` (modulo), ``**`` (exponentiation)
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For an integer type ``X``, you can use ``type(X).min`` and ``type(X).max`` to
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access the minimum and maximum value representable by the type.
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@ -83,8 +83,8 @@ for example ``uint256(0) - uint256(1) == 2**256 - 1``. You have to take these ov
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into account when designing safe smart contracts.
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The expression ``-x`` is equivalent to ``(T(0) - x)`` where
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``T`` is the type of ``x``. This means that ``-x`` will not be negative
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if the type of ``x`` is an unsigned integer type. Also, ``-x`` can be
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``T`` is the type of ``x``. It can only be applied to signed types.
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The value of ``-x`` can be
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positive if ``x`` is negative. There is another caveat also resulting
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from two's complement representation::
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@ -627,9 +627,10 @@ TypeResult IntegerType::unaryOperatorResult(Token _operator) const
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// "delete" is ok for all integer types
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if (_operator == Token::Delete)
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return TypeResult{TypeProvider::emptyTuple()};
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// we allow -, ++ and --
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else if (_operator == Token::Sub || _operator == Token::Inc ||
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_operator == Token::Dec || _operator == Token::BitNot)
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// unary negation only on signed types
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else if (_operator == Token::Sub)
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return isSigned() ? TypeResult{this} : TypeResult::err("Unary negation is only allowed for signed integers.");
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else if (_operator == Token::Inc || _operator == Token::Dec || _operator == Token::BitNot)
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return TypeResult{this};
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else
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return TypeResult::err("");
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@ -778,7 +778,7 @@ BOOST_AUTO_TEST_CASE(sign_extension)
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function run() public returns(uint256 y) {
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int64 x = -int32(0xff);
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if (x >= 0xff) return 0;
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return -uint256(x);
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return 0 - uint256(x);
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}
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}
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)";
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@ -9,7 +9,7 @@ contract C {
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returns (uint256 x1, uint256 x2, uint256 x3, uint256 x4)
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{
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a = -2;
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b = -uint8(a) * 2;
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b = (0 - uint8(a)) * 2;
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c = a * int8(120) * int8(121);
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x1 = uint256(a);
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x2 = b;
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9
test/libsolidity/syntaxTests/negation.sol
Normal file
9
test/libsolidity/syntaxTests/negation.sol
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@ -0,0 +1,9 @@
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contract test {
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function f() public pure {
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int x;
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uint y = uint(-x);
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-y;
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}
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}
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// ----
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// TypeError 4907: (97-99): Unary operator - cannot be applied to type uint256
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