From 94a49fcc4aa470b815ba0d85f20ea5f3def2d6ce Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kamil=20=C5=9Aliwak?= <kamil.sliwak@codepoets.it>
Date: Fri, 9 Oct 2020 15:42:28 +0200
Subject: [PATCH 1/2] Additional tests for ABIEncoderV1 calls using
 ABIEncoderV2 types

---
 ...sing_public_state_variable_via_v1_type.sol | 15 +++++++++++++
 ...sing_public_state_variable_via_v2_type.sol | 17 ++++++++++++++
 ...ibrary_bound_function_returning_struct.sol | 22 +++++++++++++++++++
 3 files changed, 54 insertions(+)
 create mode 100644 test/libsolidity/syntaxTests/abiEncoder/v1_accessing_public_state_variable_via_v1_type.sol
 create mode 100644 test/libsolidity/syntaxTests/abiEncoder/v1_accessing_public_state_variable_via_v2_type.sol
 create mode 100644 test/libsolidity/syntaxTests/abiEncoder/v1_call_to_v2_library_bound_function_returning_struct.sol

diff --git a/test/libsolidity/syntaxTests/abiEncoder/v1_accessing_public_state_variable_via_v1_type.sol b/test/libsolidity/syntaxTests/abiEncoder/v1_accessing_public_state_variable_via_v1_type.sol
new file mode 100644
index 000000000..e88775901
--- /dev/null
+++ b/test/libsolidity/syntaxTests/abiEncoder/v1_accessing_public_state_variable_via_v1_type.sol
@@ -0,0 +1,15 @@
+struct Item {
+    uint x;
+    uint y;
+}
+
+contract D {
+    Item[][][] public items;
+
+    function test() public view returns (uint) {
+        // The autogenerated getters to not use ABI encoder.
+        (uint a, uint b) = this.items(1, 2, 3);
+        return a + b;
+    }
+}
+// ----
diff --git a/test/libsolidity/syntaxTests/abiEncoder/v1_accessing_public_state_variable_via_v2_type.sol b/test/libsolidity/syntaxTests/abiEncoder/v1_accessing_public_state_variable_via_v2_type.sol
new file mode 100644
index 000000000..326101a37
--- /dev/null
+++ b/test/libsolidity/syntaxTests/abiEncoder/v1_accessing_public_state_variable_via_v2_type.sol
@@ -0,0 +1,17 @@
+struct Item {
+    uint x;
+    uint y;
+}
+
+contract D {
+    Item[][][] public items;
+
+    function test() public view returns (uint) {
+        // The autogenerated getters to not use ABI encoder.
+        Item memory item = this.items(1, 2, 3);
+        return item.x + item.y;
+    }
+}
+// ----
+// TypeError 7364: (202-240): Different number of components on the left hand side (1) than on the right hand side (2).
+// TypeError 9574: (202-240): Type uint256 is not implicitly convertible to expected type struct Item memory.
diff --git a/test/libsolidity/syntaxTests/abiEncoder/v1_call_to_v2_library_bound_function_returning_struct.sol b/test/libsolidity/syntaxTests/abiEncoder/v1_call_to_v2_library_bound_function_returning_struct.sol
new file mode 100644
index 000000000..eeaa6ac58
--- /dev/null
+++ b/test/libsolidity/syntaxTests/abiEncoder/v1_call_to_v2_library_bound_function_returning_struct.sol
@@ -0,0 +1,22 @@
+==== Source: A ====
+pragma experimental ABIEncoderV2;
+
+library L {
+    struct Item {
+        uint x;
+    }
+
+    function f(uint) external view returns (Item memory) {}
+}
+==== Source: B ====
+import "A";
+
+contract D {
+    using L for uint;
+
+    function test() public {
+        uint(1).f();
+    }
+}
+// ----
+// TypeError 2428: (B:86-97): The type of return parameter 1, struct L.Item, is only supported in ABIEncoderV2. Use "pragma experimental ABIEncoderV2;" to enable the feature.

From 692e4487ba7747b48f557bed8ba146ebf5057fd7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kamil=20=C5=9Aliwak?= <kamil.sliwak@codepoets.it>
Date: Fri, 9 Oct 2020 17:56:54 +0200
Subject: [PATCH 2/2] Expand docs on mixed ABIEncoderV2 and V1 use

---
 docs/layout-of-source-files.rst | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/docs/layout-of-source-files.rst b/docs/layout-of-source-files.rst
index afc6ce221..ea14c8330 100644
--- a/docs/layout-of-source-files.rst
+++ b/docs/layout-of-source-files.rst
@@ -111,6 +111,14 @@ activate it using ``pragma experimental ABIEncoderV2;`` - we kept
 the same pragma, even though it is not considered experimental
 anymore.
 
+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
+that do not without limitations. The reverse is possible only as long as the
+non-``ABIEncoderV2`` contract does not try to make calls that would require
+decoding types only supported by the new encoder. The compiler can detect this
+and will issue an error. Simply enabling ``ABIEncoderV2`` for your contract is
+enough to make the error go away.
+
 .. _smt_checker:
 
 SMTChecker