From 9538024c81368d866788a360ab81e527c57a38bd Mon Sep 17 00:00:00 2001
From: a3d4 <a3d4@pm.me>
Date: Thu, 23 Apr 2020 05:48:02 +0200
Subject: [PATCH] Fix #8711, #8277

---
 Changelog.md                                  |  1 +
 libsolidity/analysis/TypeChecker.cpp          |  2 +-
 .../tupleAssignments/empty_tuples_lhs.sol     | 24 +++++++++++++++++++
 3 files changed, 26 insertions(+), 1 deletion(-)
 create mode 100644 test/libsolidity/syntaxTests/tupleAssignments/empty_tuples_lhs.sol

diff --git a/Changelog.md b/Changelog.md
index 50a3e4d1e..30f0e3368 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -10,6 +10,7 @@ Bugfixes:
  * SMTChecker: Fix internal error when fixed points are used.
  * Type Checker: Disallow ``virtual`` and ``override`` for constructors.
  * Type Checker: Fix several internal errors by performing size and recursiveness checks of types before the full type checking.
+ * Type Checker: Fix internal error when assigning to empty tuples.
  * Type Checker: Perform recursiveness check on structs declared at the file level.
 
 Build System:
diff --git a/libsolidity/analysis/TypeChecker.cpp b/libsolidity/analysis/TypeChecker.cpp
index 17add7a66..db88f20bf 100644
--- a/libsolidity/analysis/TypeChecker.cpp
+++ b/libsolidity/analysis/TypeChecker.cpp
@@ -1289,7 +1289,7 @@ void TypeChecker::checkExpressionAssignment(Type const& _type, Expression const&
 	if (auto const* tupleExpression = dynamic_cast<TupleExpression const*>(&_expression))
 	{
 		auto const* tupleType = dynamic_cast<TupleType const*>(&_type);
-		auto const& types = tupleType && tupleExpression->components().size() > 1 ? tupleType->components() : vector<TypePointer> { &_type };
+		auto const& types = tupleType && tupleExpression->components().size() != 1 ? tupleType->components() : vector<TypePointer> { &_type };
 
 		solAssert(
 			tupleExpression->components().size() == types.size() || m_errorReporter.hasErrors(),
diff --git a/test/libsolidity/syntaxTests/tupleAssignments/empty_tuples_lhs.sol b/test/libsolidity/syntaxTests/tupleAssignments/empty_tuples_lhs.sol
new file mode 100644
index 000000000..390a3636a
--- /dev/null
+++ b/test/libsolidity/syntaxTests/tupleAssignments/empty_tuples_lhs.sol
@@ -0,0 +1,24 @@
+contract C {
+    function f0() public { (()) = 2; }
+
+    function f1() public pure { (()) = (); }
+
+    //#8711
+    function f2() internal pure returns (uint, uint) { return () = f2(); }
+
+    //#8277
+    function f3()public{return()=();}
+
+    //#8277
+    function f4 ( bytes32 hash , uint8 v , bytes32 r , bytes32 s , uint blockExpired , bytes32 salt ) public returns ( address ) {
+        require ( ( ( ) ) |= keccak256 ( abi . encodePacked ( blockExpired , salt ) ) ) ;
+        return ecrecover ( hash , v , r , s ) ;
+    }
+}
+// ----
+// TypeError: (47-48): Type int_const 2 is not implicitly convertible to expected type tuple().
+// TypeError: (178-182): Type tuple(uint256,uint256) is not implicitly convertible to expected type tuple().
+// TypeError: (166-182): Different number of arguments in return statement than in returns declaration.
+// TypeError: (399-466): Compound assignment is not allowed for tuple types.
+// TypeError: (410-466): Type bytes32 is not implicitly convertible to expected type tuple().
+// TypeError: (389-396): No matching declaration found after argument-dependent lookup.