Enable ABI coder v2 by default.

Changelog.md

@@ -5,6 +5,7 @@ Breaking Changes:
  * Code Generator: All arithmetic is checked by default. These checks can be disabled using ``unchecked { ... }``.
  * Code Generator: Cause a panic if a byte array in storage is accessed whose length is encoded incorrectly.
  * General: Remove global functions ``log0``, ``log1``, ``log2``, ``log3`` and ``log4``.
+ * General: Enable ABI coder v2 by default. Use ``pragma abicoder v1`` to use v1.
  * Type Checker: Function call options can only be given once.
  * Type System: Unary negation can only be used on signed integers, not on unsigned integers.
  * Type System: Disallow explicit conversions from negative literals and literals larger than ``type(uint160).max`` to ``address`` type.

docs/080-breaking-changes.rst

@@ -32,6 +32,9 @@ the compiler notifying you about it.
   This will save gas on errors while it still allows static analysis tools to distinguish
   these situations from a revert on invalid input, like a failing ``require``.
 
+* ABI coder v2 is enabled by default. You can switch back to ABI coder v1 by using
+  ``pragma abicoder v1;`` or enable it explicitly sing ``pragma abicoder v2;``.
+
 * If a byte array in storage is accessed whose length is encoded incorrectly, a panic is caused.
   A contract cannot get into this situation unless inline assembly is used to modify the raw representation of storage byte arrays.
 

docs/layout-of-source-files.rst

@@ -94,13 +94,11 @@ ABI Coder Pragma
 By using ``pragma abicoder v1`` or ``pragma abicoder v2`` you can
 select between the two implementations of the ABI encoder and decoder.
 
+If you do not specify the pragma, ABI coder v2 will be used by default.
+
 The new ABI coder (v2) is able to encode and decode arbitrarily nested
-arrays and structs. It might produce less optimal code and has not
-received as much testing as the old encoder, but is considered
-non-experimental as of Solidity 0.6.0. You still have to explicitly
-activate it using ``pragma abicoder v2;``. Since it will be
-activated by default starting from Solidity 0.8.0, there is the option to select
-the old coder using ``pragma abicoder v1;``.
+arrays and structs, performs more checks but might also be slightly
+more expensive.
 
 The set of types supported by the new encoder is a strict superset of
 the ones supported by the old one. Contracts that use it can interact with ones
@@ -122,6 +120,7 @@ enough to make the error go away.
   Up to Solidity 0.7.4, it was possible to select the ABI coder v2
   by using ``pragma experimental ABIEncoderV2``, but it was not possible
   to explicitly select coder v1 because it was the default.
+  ABI coder v2 has been the default since Solidity 0.8.0.
 
 .. index:: ! pragma, experimental
 

libsolidity/analysis/SyntaxChecker.cpp

@@ -74,7 +74,7 @@ void SyntaxChecker::endVisit(SourceUnit const& _sourceUnit)
 		m_errorReporter.warning(3420_error, {-1, -1, _sourceUnit.location().source}, errorString);
 	}
 	if (!m_sourceUnit->annotation().useABICoderV2.set())
-		m_sourceUnit->annotation().useABICoderV2 = false;
+		m_sourceUnit->annotation().useABICoderV2 = true;
 	m_sourceUnit = nullptr;
 }