Merge pull request #10488 from ethereum/fixDocsRevertData

Fix documentation about revert data.

docs/yul.rst

@@ -896,12 +896,11 @@ the ``dup`` and ``swap`` instructions as well as ``jump`` instructions, labels a
 
 .. note::
   The ``call*`` instructions use the ``out`` and ``outsize`` parameters to define an area in memory where
-  the return data is placed. This area is written to depending on how many bytes the called contract returns.
+  the return or failure data is placed. This area is written to depending on how many bytes the called contract returns.
   If it returns more data, only the first ``outsize`` bytes are written. You can access the rest of the data
   using the ``returndatacopy`` opcode. If it returns less data, then the remaining bytes are not touched at all.
   You need to use the ``returndatasize`` opcode to check which part of this memory area contains the return data.
-  The remaining bytes will retain their values as of before the call. If the call fails (it returns ``0``),
-  nothing is written to that area, but you can still retrieve the failure data using ``returndatacopy``.
+  The remaining bytes will retain their values as of before the call.
 
 
 In some internal dialects, there are additional functions:

test/libsolidity/semanticTests/reverts/revert_return_area.sol

@@ -0,0 +1,20 @@
+contract C {
+    fallback() external {
+        revert("abc");
+    }
+
+    function f() public returns (uint s, uint r) {
+        address x = address(this);
+        assembly {
+            mstore(0, 7)
+            s := call(sub(0, 1), x, 0, 0, 0, 0, 32)
+            r := mload(0)
+        }
+    }
+}
+
+// ====
+// compileViaYul: also
+// EVMVersion: >=byzantium
+// ----
+// f() -> 0x00, 0x08c379a000000000000000000000000000000000000000000000000000000000