Merge pull request #10003 from ethereum/more-tests-and-docs-for-mixed-abi-encoder-use-checks

More tests and some minimal docs for mixed ABI encoder use

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

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;
+    }
+}
+// ----

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.

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.