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authorChris Ward <chris.ward@ethereum.org>2019-01-07 21:27:32 +0800
committerchriseth <chris@ethereum.org>2019-01-14 23:34:35 +0800
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downloaddexon-solidity-18cceba81f1f0bf45561dc924a68309a1b1878b8.tar.gz
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Split functions docs
Diffstat (limited to 'docs')
-rw-r--r--docs/contracts.rst400
-rw-r--r--docs/contracts/functions.rst398
2 files changed, 399 insertions, 399 deletions
diff --git a/docs/contracts.rst b/docs/contracts.rst
index 859cd9e9..646e4cdc 100644
--- a/docs/contracts.rst
+++ b/docs/contracts.rst
@@ -19,405 +19,7 @@ inaccessible.
.. include:: contracts/function-modifiers.rst
.. include:: contracts/constant-state-variables.rst
-
-.. index:: ! functions
-
-.. _functions:
-
-*********
-Functions
-*********
-
-.. _function-parameters-return-variables:
-
-Function Parameters and Return Variables
-========================================
-
-As in JavaScript, functions may take parameters as input. Unlike in JavaScript
-and C, functions may also return an arbitrary number of values as output.
-
-Function Parameters
--------------------
-
-Function parameters are declared the same way as variables, and the name of
-unused parameters can be omitted.
-
-For example, if you want your contract to accept one kind of external call
-with two integers, you would use something like::
-
- pragma solidity >=0.4.16 <0.6.0;
-
- contract Simple {
- uint sum;
- function taker(uint _a, uint _b) public {
- sum = _a + _b;
- }
- }
-
-Function parameters can be used as any other local variable and they can also be assigned to.
-
-.. note::
-
- An :ref:`external function<external-function-calls>` cannot accept a
- multi-dimensional array as an input
- parameter. This functionality is possible if you enable the new
- experimental ``ABIEncoderV2`` feature by adding ``pragma experimental ABIEncoderV2;`` to your source file.
-
- An :ref:`internal function<external-function-calls>` can accept a
- multi-dimensional array without enabling the feature.
-
-.. index:: return array, return string, array, string, array of strings, dynamic array, variably sized array, return struct, struct
-
-Return Variables
-----------------
-
-Function return variables are declared with the same syntax after the
-``returns`` keyword.
-
-For example, suppose you want to return two results: the sum and the product of
-two integers passed as function parameters, then you use something like::
-
- pragma solidity >=0.4.16 <0.6.0;
-
- contract Simple {
- function arithmetic(uint _a, uint _b)
- public
- pure
- returns (uint o_sum, uint o_product)
- {
- o_sum = _a + _b;
- o_product = _a * _b;
- }
- }
-
-The names of return variables can be omitted.
-Return variables can be used as any other local variable and they
-are initialized with their :ref:`default value <default-value>` and have that value unless explicitly set.
-
-You can either explicitly assign to return variables and
-then leave the function using ``return;``,
-or you can provide return values
-(either a single or :ref:`multiple ones<multi-return>`) directly with the ``return``
-statement::
-
- pragma solidity >=0.4.16 <0.6.0;
-
- contract Simple {
- function arithmetic(uint _a, uint _b)
- public
- pure
- returns (uint o_sum, uint o_product)
- {
- return (_a + _b, _a * _b);
- }
- }
-
-This form is equivalent to first assigning values to the
-return variables and then using ``return;`` to leave the function.
-
-.. note::
- You cannot return some types from non-internal functions, notably
- multi-dimensional dynamic arrays and structs. If you enable the
- new experimental ``ABIEncoderV2`` feature by adding ``pragma experimental
- ABIEncoderV2;`` to your source file then more types are available, but
- ``mapping`` types are still limited to inside a single contract and you
- cannot transfer them.
-
-.. _multi-return:
-
-Returning Multiple Values
--------------------------
-
-When a function has multiple return types, the statement ``return (v0, v1, ..., vn)`` can be used to return multiple values.
-The number of components must be the same as the number of return types.
-
-.. index:: ! view function, function;view
-
-.. _view-functions:
-
-View Functions
-==============
-
-Functions can be declared ``view`` in which case they promise not to modify the state.
-
-.. note::
- If the compiler's EVM target is Byzantium or newer (default) the opcode
- ``STATICCALL`` is used for ``view`` functions which enforces the state
- to stay unmodified as part of the EVM execution. For library ``view`` functions
- ``DELEGATECALL`` is used, because there is no combined ``DELEGATECALL`` and ``STATICCALL``.
- This means library ``view`` functions do not have run-time checks that prevent state
- modifications. This should not impact security negatively because library code is
- usually known at compile-time and the static checker performs compile-time checks.
-
-The following statements are considered modifying the state:
-
-#. Writing to state variables.
-#. :ref:`Emitting events <events>`.
-#. :ref:`Creating other contracts <creating-contracts>`.
-#. Using ``selfdestruct``.
-#. Sending Ether via calls.
-#. Calling any function not marked ``view`` or ``pure``.
-#. Using low-level calls.
-#. Using inline assembly that contains certain opcodes.
-
-::
-
- pragma solidity ^0.5.0;
-
- contract C {
- function f(uint a, uint b) public view returns (uint) {
- return a * (b + 42) + now;
- }
- }
-
-.. note::
- ``constant`` on functions used to be an alias to ``view``, but this was dropped in version 0.5.0.
-
-.. note::
- Getter methods are automatically marked ``view``.
-
-.. note::
- Prior to version 0.5.0, the compiler did not use the ``STATICCALL`` opcode
- for ``view`` functions.
- This enabled state modifications in ``view`` functions through the use of
- invalid explicit type conversions.
- By using ``STATICCALL`` for ``view`` functions, modifications to the
- state are prevented on the level of the EVM.
-
-.. index:: ! pure function, function;pure
-
-.. _pure-functions:
-
-Pure Functions
-==============
-
-Functions can be declared ``pure`` in which case they promise not to read from or modify the state.
-
-.. note::
- If the compiler's EVM target is Byzantium or newer (default) the opcode ``STATICCALL`` is used,
- which does not guarantee that the state is not read, but at least that it is not modified.
-
-In addition to the list of state modifying statements explained above, the following are considered reading from the state:
-
-#. Reading from state variables.
-#. Accessing ``address(this).balance`` or ``<address>.balance``.
-#. Accessing any of the members of ``block``, ``tx``, ``msg`` (with the exception of ``msg.sig`` and ``msg.data``).
-#. Calling any function not marked ``pure``.
-#. Using inline assembly that contains certain opcodes.
-
-::
-
- pragma solidity ^0.5.0;
-
- contract C {
- function f(uint a, uint b) public pure returns (uint) {
- return a * (b + 42);
- }
- }
-
-Pure functions are able to use the `revert()` and `require()` functions to revert
-potential state changes when an :ref:`error occurs <assert-and-require>`.
-
-Reverting a state change is not considered a "state modification", as only changes to the
-state made previously in code that did not have the ``view`` or ``pure`` restriction
-are reverted and that code has the option to catch the ``revert`` and not pass it on.
-
-This behaviour is also in line with the ``STATICCALL`` opcode.
-
-.. warning::
- It is not possible to prevent functions from reading the state at the level
- of the EVM, it is only possible to prevent them from writing to the state
- (i.e. only ``view`` can be enforced at the EVM level, ``pure`` can not).
-
-.. note::
- Prior to version 0.5.0, the compiler did not use the ``STATICCALL`` opcode
- for ``pure`` functions.
- This enabled state modifications in ``pure`` functions through the use of
- invalid explicit type conversions.
- By using ``STATICCALL`` for ``pure`` functions, modifications to the
- state are prevented on the level of the EVM.
-
-.. note::
- Prior to version 0.4.17 the compiler did not enforce that ``pure`` is not reading the state.
- It is a compile-time type check, which can be circumvented doing invalid explicit conversions
- between contract types, because the compiler can verify that the type of the contract does
- not do state-changing operations, but it cannot check that the contract that will be called
- at runtime is actually of that type.
-
-.. index:: ! fallback function, function;fallback
-
-.. _fallback-function:
-
-Fallback Function
-=================
-
-A contract can have exactly one unnamed function. This function cannot have
-arguments, cannot return anything and has to have ``external`` visibility.
-It is executed on a call to the contract if none of the other
-functions match the given function identifier (or if no data was supplied at
-all).
-
-Furthermore, this function is executed whenever the contract receives plain
-Ether (without data). Additionally, in order to receive Ether, the fallback function
-must be marked ``payable``. If no such function exists, the contract cannot receive
-Ether through regular transactions.
-
-In the worst case, the fallback function can only rely on 2300 gas being
-available (for example when `send` or `transfer` is used), leaving little
-room to perform other operations except basic logging. The following operations
-will consume more gas than the 2300 gas stipend:
-
-- Writing to storage
-- Creating a contract
-- Calling an external function which consumes a large amount of gas
-- Sending Ether
-
-Like any function, the fallback function can execute complex operations as long as there is enough gas passed on to it.
-
-.. note::
- Even though the fallback function cannot have arguments, one can still use ``msg.data`` to retrieve
- any payload supplied with the call.
-
-.. warning::
- The fallback function is also executed if the caller meant to call
- a function that is not available. If you want to implement the fallback
- function only to receive ether, you should add a check
- like ``require(msg.data.length == 0)`` to prevent invalid calls.
-
-.. warning::
- Contracts that receive Ether directly (without a function call, i.e. using ``send`` or ``transfer``)
- but do not define a fallback function
- throw an exception, sending back the Ether (this was different
- before Solidity v0.4.0). So if you want your contract to receive Ether,
- you have to implement a payable fallback function.
-
-.. warning::
- A contract without a payable fallback function can receive Ether as a recipient of a `coinbase transaction` (aka `miner block reward`)
- or as a destination of a ``selfdestruct``.
-
- A contract cannot react to such Ether transfers and thus also cannot reject them. This is a design choice of the EVM and Solidity cannot work around it.
-
- It also means that ``address(this).balance`` can be higher than the sum of some manual accounting implemented in a contract (i.e. having a counter updated in the fallback function).
-
-::
-
- pragma solidity ^0.5.0;
-
- contract Test {
- // This function is called for all messages sent to
- // this contract (there is no other function).
- // Sending Ether to this contract will cause an exception,
- // because the fallback function does not have the `payable`
- // modifier.
- function() external { x = 1; }
- uint x;
- }
-
-
- // This contract keeps all Ether sent to it with no way
- // to get it back.
- contract Sink {
- function() external payable { }
- }
-
- contract Caller {
- function callTest(Test test) public returns (bool) {
- (bool success,) = address(test).call(abi.encodeWithSignature("nonExistingFunction()"));
- require(success);
- // results in test.x becoming == 1.
-
- // address(test) will not allow to call ``send`` directly, since ``test`` has no payable
- // fallback function. It has to be converted to the ``address payable`` type via an
- // intermediate conversion to ``uint160`` to even allow calling ``send`` on it.
- address payable testPayable = address(uint160(address(test)));
-
- // If someone sends ether to that contract,
- // the transfer will fail, i.e. this returns false here.
- return testPayable.send(2 ether);
- }
- }
-
-.. index:: ! overload
-
-.. _overload-function:
-
-Function Overloading
-====================
-
-A contract can have multiple functions of the same name but with different parameter
-types.
-This process is called "overloading" and also applies to inherited functions.
-The following example shows overloading of the function
-``f`` in the scope of contract ``A``.
-
-::
-
- pragma solidity >=0.4.16 <0.6.0;
-
- contract A {
- function f(uint _in) public pure returns (uint out) {
- out = _in;
- }
-
- function f(uint _in, bool _really) public pure returns (uint out) {
- if (_really)
- out = _in;
- }
- }
-
-Overloaded functions are also present in the external interface. It is an error if two
-externally visible functions differ by their Solidity types but not by their external types.
-
-::
-
- pragma solidity >=0.4.16 <0.6.0;
-
- // This will not compile
- contract A {
- function f(B _in) public pure returns (B out) {
- out = _in;
- }
-
- function f(address _in) public pure returns (address out) {
- out = _in;
- }
- }
-
- contract B {
- }
-
-
-Both ``f`` function overloads above end up accepting the address type for the ABI although
-they are considered different inside Solidity.
-
-Overload resolution and Argument matching
------------------------------------------
-
-Overloaded functions are selected by matching the function declarations in the current scope
-to the arguments supplied in the function call. Functions are selected as overload candidates
-if all arguments can be implicitly converted to the expected types. If there is not exactly one
-candidate, resolution fails.
-
-.. note::
- Return parameters are not taken into account for overload resolution.
-
-::
-
- pragma solidity >=0.4.16 <0.6.0;
-
- contract A {
- function f(uint8 _in) public pure returns (uint8 out) {
- out = _in;
- }
-
- function f(uint256 _in) public pure returns (uint256 out) {
- out = _in;
- }
- }
-
-Calling ``f(50)`` would create a type error since ``50`` can be implicitly converted both to ``uint8``
-and ``uint256`` types. On another hand ``f(256)`` would resolve to ``f(uint256)`` overload as ``256`` cannot be implicitly
-converted to ``uint8``.
+.. include:: contracts/functions.rst
.. include:: contracts/events.rst
diff --git a/docs/contracts/functions.rst b/docs/contracts/functions.rst
new file mode 100644
index 00000000..76245952
--- /dev/null
+++ b/docs/contracts/functions.rst
@@ -0,0 +1,398 @@
+.. index:: ! functions
+
+.. _functions:
+
+*********
+Functions
+*********
+
+.. _function-parameters-return-variables:
+
+Function Parameters and Return Variables
+========================================
+
+As in JavaScript, functions may take parameters as input. Unlike in JavaScript
+and C, functions may also return an arbitrary number of values as output.
+
+Function Parameters
+-------------------
+
+Function parameters are declared the same way as variables, and the name of
+unused parameters can be omitted.
+
+For example, if you want your contract to accept one kind of external call
+with two integers, you would use something like::
+
+ pragma solidity >=0.4.16 <0.6.0;
+
+ contract Simple {
+ uint sum;
+ function taker(uint _a, uint _b) public {
+ sum = _a + _b;
+ }
+ }
+
+Function parameters can be used as any other local variable and they can also be assigned to.
+
+.. note::
+
+ An :ref:`external function<external-function-calls>` cannot accept a
+ multi-dimensional array as an input
+ parameter. This functionality is possible if you enable the new
+ experimental ``ABIEncoderV2`` feature by adding ``pragma experimental ABIEncoderV2;`` to your source file.
+
+ An :ref:`internal function<external-function-calls>` can accept a
+ multi-dimensional array without enabling the feature.
+
+.. index:: return array, return string, array, string, array of strings, dynamic array, variably sized array, return struct, struct
+
+Return Variables
+----------------
+
+Function return variables are declared with the same syntax after the
+``returns`` keyword.
+
+For example, suppose you want to return two results: the sum and the product of
+two integers passed as function parameters, then you use something like::
+
+ pragma solidity >=0.4.16 <0.6.0;
+
+ contract Simple {
+ function arithmetic(uint _a, uint _b)
+ public
+ pure
+ returns (uint o_sum, uint o_product)
+ {
+ o_sum = _a + _b;
+ o_product = _a * _b;
+ }
+ }
+
+The names of return variables can be omitted.
+Return variables can be used as any other local variable and they
+are initialized with their :ref:`default value <default-value>` and have that value unless explicitly set.
+
+You can either explicitly assign to return variables and
+then leave the function using ``return;``,
+or you can provide return values
+(either a single or :ref:`multiple ones<multi-return>`) directly with the ``return``
+statement::
+
+ pragma solidity >=0.4.16 <0.6.0;
+
+ contract Simple {
+ function arithmetic(uint _a, uint _b)
+ public
+ pure
+ returns (uint o_sum, uint o_product)
+ {
+ return (_a + _b, _a * _b);
+ }
+ }
+
+This form is equivalent to first assigning values to the
+return variables and then using ``return;`` to leave the function.
+
+.. note::
+ You cannot return some types from non-internal functions, notably
+ multi-dimensional dynamic arrays and structs. If you enable the
+ new experimental ``ABIEncoderV2`` feature by adding ``pragma experimental
+ ABIEncoderV2;`` to your source file then more types are available, but
+ ``mapping`` types are still limited to inside a single contract and you
+ cannot transfer them.
+
+.. _multi-return:
+
+Returning Multiple Values
+-------------------------
+
+When a function has multiple return types, the statement ``return (v0, v1, ..., vn)`` can be used to return multiple values.
+The number of components must be the same as the number of return types.
+
+.. index:: ! view function, function;view
+
+.. _view-functions:
+
+View Functions
+==============
+
+Functions can be declared ``view`` in which case they promise not to modify the state.
+
+.. note::
+ If the compiler's EVM target is Byzantium or newer (default) the opcode
+ ``STATICCALL`` is used for ``view`` functions which enforces the state
+ to stay unmodified as part of the EVM execution. For library ``view`` functions
+ ``DELEGATECALL`` is used, because there is no combined ``DELEGATECALL`` and ``STATICCALL``.
+ This means library ``view`` functions do not have run-time checks that prevent state
+ modifications. This should not impact security negatively because library code is
+ usually known at compile-time and the static checker performs compile-time checks.
+
+The following statements are considered modifying the state:
+
+#. Writing to state variables.
+#. :ref:`Emitting events <events>`.
+#. :ref:`Creating other contracts <creating-contracts>`.
+#. Using ``selfdestruct``.
+#. Sending Ether via calls.
+#. Calling any function not marked ``view`` or ``pure``.
+#. Using low-level calls.
+#. Using inline assembly that contains certain opcodes.
+
+::
+
+ pragma solidity ^0.5.0;
+
+ contract C {
+ function f(uint a, uint b) public view returns (uint) {
+ return a * (b + 42) + now;
+ }
+ }
+
+.. note::
+ ``constant`` on functions used to be an alias to ``view``, but this was dropped in version 0.5.0.
+
+.. note::
+ Getter methods are automatically marked ``view``.
+
+.. note::
+ Prior to version 0.5.0, the compiler did not use the ``STATICCALL`` opcode
+ for ``view`` functions.
+ This enabled state modifications in ``view`` functions through the use of
+ invalid explicit type conversions.
+ By using ``STATICCALL`` for ``view`` functions, modifications to the
+ state are prevented on the level of the EVM.
+
+.. index:: ! pure function, function;pure
+
+.. _pure-functions:
+
+Pure Functions
+==============
+
+Functions can be declared ``pure`` in which case they promise not to read from or modify the state.
+
+.. note::
+ If the compiler's EVM target is Byzantium or newer (default) the opcode ``STATICCALL`` is used,
+ which does not guarantee that the state is not read, but at least that it is not modified.
+
+In addition to the list of state modifying statements explained above, the following are considered reading from the state:
+
+#. Reading from state variables.
+#. Accessing ``address(this).balance`` or ``<address>.balance``.
+#. Accessing any of the members of ``block``, ``tx``, ``msg`` (with the exception of ``msg.sig`` and ``msg.data``).
+#. Calling any function not marked ``pure``.
+#. Using inline assembly that contains certain opcodes.
+
+::
+
+ pragma solidity ^0.5.0;
+
+ contract C {
+ function f(uint a, uint b) public pure returns (uint) {
+ return a * (b + 42);
+ }
+ }
+
+Pure functions are able to use the `revert()` and `require()` functions to revert
+potential state changes when an :ref:`error occurs <assert-and-require>`.
+
+Reverting a state change is not considered a "state modification", as only changes to the
+state made previously in code that did not have the ``view`` or ``pure`` restriction
+are reverted and that code has the option to catch the ``revert`` and not pass it on.
+
+This behaviour is also in line with the ``STATICCALL`` opcode.
+
+.. warning::
+ It is not possible to prevent functions from reading the state at the level
+ of the EVM, it is only possible to prevent them from writing to the state
+ (i.e. only ``view`` can be enforced at the EVM level, ``pure`` can not).
+
+.. note::
+ Prior to version 0.5.0, the compiler did not use the ``STATICCALL`` opcode
+ for ``pure`` functions.
+ This enabled state modifications in ``pure`` functions through the use of
+ invalid explicit type conversions.
+ By using ``STATICCALL`` for ``pure`` functions, modifications to the
+ state are prevented on the level of the EVM.
+
+.. note::
+ Prior to version 0.4.17 the compiler did not enforce that ``pure`` is not reading the state.
+ It is a compile-time type check, which can be circumvented doing invalid explicit conversions
+ between contract types, because the compiler can verify that the type of the contract does
+ not do state-changing operations, but it cannot check that the contract that will be called
+ at runtime is actually of that type.
+
+.. index:: ! fallback function, function;fallback
+
+.. _fallback-function:
+
+Fallback Function
+=================
+
+A contract can have exactly one unnamed function. This function cannot have
+arguments, cannot return anything and has to have ``external`` visibility.
+It is executed on a call to the contract if none of the other
+functions match the given function identifier (or if no data was supplied at
+all).
+
+Furthermore, this function is executed whenever the contract receives plain
+Ether (without data). Additionally, in order to receive Ether, the fallback function
+must be marked ``payable``. If no such function exists, the contract cannot receive
+Ether through regular transactions.
+
+In the worst case, the fallback function can only rely on 2300 gas being
+available (for example when `send` or `transfer` is used), leaving little
+room to perform other operations except basic logging. The following operations
+will consume more gas than the 2300 gas stipend:
+
+- Writing to storage
+- Creating a contract
+- Calling an external function which consumes a large amount of gas
+- Sending Ether
+
+Like any function, the fallback function can execute complex operations as long as there is enough gas passed on to it.
+
+.. note::
+ Even though the fallback function cannot have arguments, one can still use ``msg.data`` to retrieve
+ any payload supplied with the call.
+
+.. warning::
+ The fallback function is also executed if the caller meant to call
+ a function that is not available. If you want to implement the fallback
+ function only to receive ether, you should add a check
+ like ``require(msg.data.length == 0)`` to prevent invalid calls.
+
+.. warning::
+ Contracts that receive Ether directly (without a function call, i.e. using ``send`` or ``transfer``)
+ but do not define a fallback function
+ throw an exception, sending back the Ether (this was different
+ before Solidity v0.4.0). So if you want your contract to receive Ether,
+ you have to implement a payable fallback function.
+
+.. warning::
+ A contract without a payable fallback function can receive Ether as a recipient of a `coinbase transaction` (aka `miner block reward`)
+ or as a destination of a ``selfdestruct``.
+
+ A contract cannot react to such Ether transfers and thus also cannot reject them. This is a design choice of the EVM and Solidity cannot work around it.
+
+ It also means that ``address(this).balance`` can be higher than the sum of some manual accounting implemented in a contract (i.e. having a counter updated in the fallback function).
+
+::
+
+ pragma solidity ^0.5.0;
+
+ contract Test {
+ // This function is called for all messages sent to
+ // this contract (there is no other function).
+ // Sending Ether to this contract will cause an exception,
+ // because the fallback function does not have the `payable`
+ // modifier.
+ function() external { x = 1; }
+ uint x;
+ }
+
+
+ // This contract keeps all Ether sent to it with no way
+ // to get it back.
+ contract Sink {
+ function() external payable { }
+ }
+
+ contract Caller {
+ function callTest(Test test) public returns (bool) {
+ (bool success,) = address(test).call(abi.encodeWithSignature("nonExistingFunction()"));
+ require(success);
+ // results in test.x becoming == 1.
+
+ // address(test) will not allow to call ``send`` directly, since ``test`` has no payable
+ // fallback function. It has to be converted to the ``address payable`` type via an
+ // intermediate conversion to ``uint160`` to even allow calling ``send`` on it.
+ address payable testPayable = address(uint160(address(test)));
+
+ // If someone sends ether to that contract,
+ // the transfer will fail, i.e. this returns false here.
+ return testPayable.send(2 ether);
+ }
+ }
+
+.. index:: ! overload
+
+.. _overload-function:
+
+Function Overloading
+====================
+
+A contract can have multiple functions of the same name but with different parameter
+types.
+This process is called "overloading" and also applies to inherited functions.
+The following example shows overloading of the function
+``f`` in the scope of contract ``A``.
+
+::
+
+ pragma solidity >=0.4.16 <0.6.0;
+
+ contract A {
+ function f(uint _in) public pure returns (uint out) {
+ out = _in;
+ }
+
+ function f(uint _in, bool _really) public pure returns (uint out) {
+ if (_really)
+ out = _in;
+ }
+ }
+
+Overloaded functions are also present in the external interface. It is an error if two
+externally visible functions differ by their Solidity types but not by their external types.
+
+::
+
+ pragma solidity >=0.4.16 <0.6.0;
+
+ // This will not compile
+ contract A {
+ function f(B _in) public pure returns (B out) {
+ out = _in;
+ }
+
+ function f(address _in) public pure returns (address out) {
+ out = _in;
+ }
+ }
+
+ contract B {
+ }
+
+
+Both ``f`` function overloads above end up accepting the address type for the ABI although
+they are considered different inside Solidity.
+
+Overload resolution and Argument matching
+-----------------------------------------
+
+Overloaded functions are selected by matching the function declarations in the current scope
+to the arguments supplied in the function call. Functions are selected as overload candidates
+if all arguments can be implicitly converted to the expected types. If there is not exactly one
+candidate, resolution fails.
+
+.. note::
+ Return parameters are not taken into account for overload resolution.
+
+::
+
+ pragma solidity >=0.4.16 <0.6.0;
+
+ contract A {
+ function f(uint8 _in) public pure returns (uint8 out) {
+ out = _in;
+ }
+
+ function f(uint256 _in) public pure returns (uint256 out) {
+ out = _in;
+ }
+ }
+
+Calling ``f(50)`` would create a type error since ``50`` can be implicitly converted both to ``uint8``
+and ``uint256`` types. On another hand ``f(256)`` would resolve to ``f(uint256)`` overload as ``256`` cannot be implicitly
+converted to ``uint8``.