Merge pull request #8907 from ethereum/licenseIdentifier

Check for SPDX license identifiers.

Author: chriseth

docs/050-breaking-changes.rst

@@ -292,6 +292,7 @@ Consider you have the following pre-0.5.0 contract already deployed:
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity ^0.4.25;
     // This will report a warning until version 0.4.25 of the compiler
     // This will not compile after 0.5.0
@@ -309,6 +310,7 @@ This will no longer compile with Solidity v0.5.0. However, you can define a comp
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.5.0 <0.7.0;
     interface OldContract {
         function someOldFunction(uint8 a) external;
@@ -326,6 +328,7 @@ Given the interface defined above, you can now easily use the already deployed p
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.5.0 <0.7.0;
 
     interface OldContract {
@@ -347,6 +350,7 @@ commandline compiler for linking):
 ::
 
     // This will not compile after 0.6.0
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.5.0 <0.5.99;
 
     library OldLibrary {
@@ -370,6 +374,7 @@ Old version:
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity ^0.4.25;
     // This will not compile after 0.5.0
 
@@ -432,6 +437,7 @@ New version:
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.5.0 <0.5.99;
     // This will not compile after 0.6.0
 

docs/abi-spec.rst

@@ -232,6 +232,7 @@ Given the contract:
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.16 <0.7.0;
 
     contract Foo {
@@ -535,6 +536,7 @@ For example,
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.5.0 <0.7.0;
 
 
@@ -583,6 +585,7 @@ As an example, the code
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.19 <0.7.0;
     pragma experimental ABIEncoderV2;
 

docs/assembly.rst

@@ -41,6 +41,7 @@ without a compiler change.
 
 .. code::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.16 <0.7.0;
 
     library GetCode {
@@ -66,6 +67,7 @@ efficient code, for example:
 
 .. code::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.16 <0.7.0;
 
 
@@ -136,6 +138,7 @@ Local Solidity variables are available for assignments, for example:
 
 .. code::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.16 <0.7.0;
 
     contract C {

docs/common-patterns.rst

@@ -27,6 +27,7 @@ you receive the funds of the person who is now the richest.
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.5.0 <0.7.0;
 
     contract WithdrawalContract {
@@ -60,6 +61,7 @@ This is as opposed to the more intuitive sending pattern:
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.5.0 <0.7.0;
 
     contract SendContract {
@@ -121,6 +123,7 @@ restrictions highly readable.
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.22 <0.7.0;
 
     contract AccessRestriction {
@@ -273,6 +276,7 @@ function finishes.
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.22 <0.7.0;
 
     contract StateMachine {

docs/contracts/abstract-contracts.rst

@@ -13,6 +13,7 @@ This can be done by using the ``abstract`` keyword as shown in the following exa
 defined as abstract, because the function ``utterance()`` was defined, but no implementation was
 provided (no implementation body ``{ }`` was given).::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.6.0 <0.7.0;
 
     abstract contract Feline {
@@ -22,6 +23,7 @@ provided (no implementation body ``{ }`` was given).::
 Such abstract contracts can not be instantiated directly. This is also true, if an abstract contract itself does implement
 all defined functions. The usage of an abstract contract as a base class is shown in the following example::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity ^0.6.0;
 
     abstract contract Feline {

docs/contracts/constant-state-variables.rst

@@ -17,6 +17,7 @@ Not all types for constants and immutables are implemented at this time. The onl
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >0.6.4 <0.7.0;
 
     contract C {

docs/contracts/creating-contracts.rst

@@ -34,6 +34,7 @@ This means that cyclic creation dependencies are impossible.
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.22 <0.7.0;
 
 

docs/contracts/events.rst

@@ -65,6 +65,7 @@ is that they are cheaper to deploy and call.
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.21 <0.7.0;
 
     contract ClientReceipt {
@@ -138,6 +139,7 @@ as topics. The event call above can be performed in the same way as
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.10 <0.7.0;
 
     contract C {

docs/contracts/function-modifiers.rst

@@ -17,6 +17,7 @@ if they are marked ``virtual``. For details, please see
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.5.0 <0.7.0;
 
     contract owned {

docs/contracts/functions.rst

@@ -23,6 +23,7 @@ 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 the following::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.16 <0.7.0;
 
     contract Simple {
@@ -55,6 +56,7 @@ Function return variables are declared with the same syntax after the
 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::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.16 <0.7.0;
 
     contract Simple {
@@ -79,6 +81,7 @@ or you can provide return values
 (either a single or :ref:`multiple ones<multi-return>`) directly with the ``return``
 statement::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.16 <0.7.0;
 
     contract Simple {
@@ -142,6 +145,7 @@ The following statements are considered modifying the state:
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.5.0 <0.7.0;
 
     contract C {
@@ -187,6 +191,7 @@ In addition to the list of state modifying statements explained above, the follo
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.5.0 <0.7.0;
 
     contract C {
@@ -280,6 +285,7 @@ Below you can see an example of a Sink contract that uses function ``receive``.
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity ^0.6.0;
 
     // This contract keeps all Ether sent to it with no way
@@ -335,6 +341,7 @@ operations as long as there is enough gas passed on to it.
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.6.2 <0.7.0;
 
     contract Test {
@@ -407,6 +414,7 @@ The following example shows overloading of the function
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.16 <0.7.0;
 
     contract A {
@@ -425,6 +433,7 @@ externally visible functions differ by their Solidity types but not by their ext
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.16 <0.7.0;
 
     // This will not compile
@@ -458,6 +467,7 @@ candidate, resolution fails.
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.16 <0.7.0;
 
     contract A {

docs/contracts/inheritance.rst

@@ -38,6 +38,7 @@ Details are given in the following example.
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity ^0.6.0;
 
 
@@ -125,6 +126,7 @@ Note that above, we call ``Destructible.destroy()`` to "forward" the
 destruction request. The way this is done is problematic, as
 seen in the following example::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity ^0.6.0;
 
     contract owned {
@@ -154,6 +156,7 @@ A call to ``Final.destroy()`` will call ``Base2.destroy`` because we specify it
 explicitly in the final override, but this function will bypass
 ``Base1.destroy``. The way around this is to use ``super``::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.6.0 <0.7.0;
 
     contract owned {
@@ -204,6 +207,7 @@ use the ``override`` keyword in the function header as shown in this example:
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.6.0 <0.7.0;
 
     contract Base
@@ -227,6 +231,7 @@ bases, it has to explicitly override it:
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.6.0 <0.7.0;
 
     contract Base1
@@ -253,6 +258,7 @@ that already overrides all other functions.
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.6.0 <0.7.0;
 
     contract A { function f() public pure{} }
@@ -293,6 +299,7 @@ of the variable:
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.6.0 <0.7.0;
 
     contract A
@@ -324,6 +331,7 @@ and the ``override`` keyword must be used in the overriding modifier:
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.6.0 <0.7.0;
 
     contract Base
@@ -342,6 +350,7 @@ explicitly:
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.6.0 <0.7.0;
 
     contract Base1
@@ -389,6 +398,7 @@ equivalent to ``constructor() public {}``. For example:
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.5.0 <0.7.0;
 
     contract A {
@@ -419,6 +429,7 @@ The constructors of all the base contracts will be called following the
 linearization rules explained below. If the base constructors have arguments,
 derived contracts need to specify all of them. This can be done in two ways::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.22 <0.7.0;
 
     contract Base {
@@ -478,6 +489,7 @@ error "Linearization of inheritance graph impossible".
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.0 <0.7.0;
 
     contract X {}
@@ -498,6 +510,7 @@ One area where inheritance linearization is especially important and perhaps not
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.4.22 <0.7.0;
 
     contract Base1 {

docs/contracts/interfaces.rst

@@ -22,6 +22,7 @@ Interfaces are denoted by their own keyword:
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.6.2 <0.7.0;
 
     interface Token {
@@ -42,6 +43,7 @@ inheritance.
 
 ::
 
+    // SPDX-License-Identifier: GPL-3.0
     pragma solidity >=0.6.2 <0.7.0;
 
     interface ParentA {