Split fallback function and introduce "fallback()" and "receive()" syntax.

test/libsolidity/syntaxTests/fallback/arguments.sol

@@ -0,0 +1,5 @@
+contract C {
+    fallback(uint256) external {}
+}
+// ----
+// TypeError: (25-34): Fallback function cannot take parameters.

test/libsolidity/syntaxTests/fallback/default_visibility.sol

@@ -1,6 +1,6 @@
 contract C {
     // Check that visibility is also enforced for the fallback function.
-    function() {}
+    fallback() {}
 }
 // ----
 // SyntaxError: (90-103): No visibility specified. Did you intend to add "external"?

test/libsolidity/syntaxTests/fallback/fallback_as_function_name.sol

@@ -0,0 +1,5 @@
+contract C {
+    function fallback() external pure {}
+}
+// ----
+// Warning: (26-34): This function is named "fallback" but is not the fallback function of the contract. If you intend this to be a fallback function, use "fallback(...) { ... }" without the "function" keyword to define it.

test/libsolidity/syntaxTests/fallback/old_syntax.sol

@@ -0,0 +1,5 @@
+contract C {
+    function() external {}
+}
+// ----
+// ParserError: (37-38): Expected a state variable declaration. If you intended this as a fallback function or a function to handle plain ether transactions, use the "fallback" keyword or the "ether" keyword instead.

test/libsolidity/syntaxTests/fallback/payable_fallback_with_inherited_receive.sol

@@ -0,0 +1,6 @@
+contract A {
+    receive() external payable { }
+}
+contract C is A {
+    fallback() external payable { }
+}

test/libsolidity/syntaxTests/fallback/payable_fallback_without_receive_empty.sol

@@ -0,0 +1,3 @@
+contract C {
+    fallback() external payable { }
+}

test/libsolidity/syntaxTests/fallback/payable_fallback_without_receive_nonempty.sol

@@ -0,0 +1,6 @@
+contract C {
+    fallback() external payable { }
+    function f() public pure { }
+}
+// ----
+// Warning: (0-83): This contract has a payable fallback function, but no receive ether function. Consider adding a receive ether function.

test/libsolidity/syntaxTests/fallback/payable_fallback_without_receive_nonempty_by_inheritance.sol

@@ -0,0 +1,8 @@
+contract A {
+    function f() external pure {}
+}
+contract C is A {
+    fallback() external payable { }
+}
+// ----
+// Warning: (49-104): This contract has a payable fallback function, but no receive ether function. Consider adding a receive ether function.

test/libsolidity/syntaxTests/fallback/payable_fallback_without_receive_only_internal.sol

@@ -0,0 +1,4 @@
+contract C {
+    fallback() external payable { }
+    function f() internal pure { }
+}

test/libsolidity/syntaxTests/fallback/pure_modifier.sol

@@ -1,6 +1,6 @@
 contract C {
     uint x;
-    function() external pure { x = 2; }
+    fallback() external pure { x = 2; }
 }
 // ----
 // TypeError: (29-64): Fallback function must be payable or non-payable, but is "pure".

test/libsolidity/syntaxTests/fallback/return_value_number.sol

@@ -0,0 +1,5 @@
+contract C {
+    fallback() external returns (bytes memory, bytes memory) {}
+}
+// ----
+// TypeError: (45-73): Fallback function can only have a single "bytes memory" return value.

test/libsolidity/syntaxTests/fallback/return_value_type.sol

@@ -0,0 +1,5 @@
+contract C {
+    fallback() external returns (uint256) {}
+}
+// ----
+// TypeError: (45-54): Fallback function can only have a single "bytes memory" return value.

test/libsolidity/syntaxTests/fallback/return_value_unsupported.sol

@@ -0,0 +1,5 @@
+contract C {
+    fallback() external returns (bytes memory) {}
+}
+// ----
+// TypeError: (45-59): Return values for fallback functions are not yet implemented.

test/libsolidity/syntaxTests/fallback/view_modifier.sol

@@ -1,6 +1,6 @@
 contract C {
     uint x;
-    function() external view { x = 2; }
+    fallback() external view { x = 2; }
 }
 // ----
 // TypeError: (29-64): Fallback function must be payable or non-payable, but is "view".

test/libsolidity/syntaxTests/imports/simple_alias.sol

@@ -1,4 +1,4 @@
 ==== Source: a ====
 contract A {}
 ==== Source: dir/a/b/c ====
-import "../../.././a" as x; contract B is x.A { function() external { x.A r = x.A(20); r; } }
+import "../../.././a" as x; contract B is x.A { fallback() external { x.A r = x.A(20); r; } }

test/libsolidity/syntaxTests/inheritance/fallback_receive/fallback_overrides_receive.sol

@@ -0,0 +1,8 @@
+contract C {
+	receive() external payable {}
+}
+contract D is C {
+	fallback() override external {}
+}
+// ----
+// TypeError: (76-84): Function has override specified but does not override anything.

test/libsolidity/syntaxTests/inheritance/fallback_receive/fallback_with_override.sol

@@ -0,0 +1,6 @@
+contract C {
+	fallback() external {}
+}
+contract D is C {
+	fallback() override external {}
+}

test/libsolidity/syntaxTests/inheritance/fallback_receive/fallback_with_override_intermediate.sol

@@ -0,0 +1,8 @@
+contract C {
+	fallback() external {}
+}
+contract D is C {
+}
+contract E is D {
+	fallback() override external {}
+}

test/libsolidity/syntaxTests/inheritance/fallback_receive/fallback_without_override.sol

@@ -0,0 +1,8 @@
+contract C {
+	fallback() external {}
+}
+contract D is C {
+	fallback() external {}
+}
+// ----
+// TypeError: (58-80): Overriding function is missing 'override' specifier.

test/libsolidity/syntaxTests/inheritance/fallback_receive/fallback_without_override_intermediate.sol

@@ -0,0 +1,10 @@
+contract C {
+	fallback() external {}
+}
+contract D is C {
+}
+contract E is D {
+	fallback() external {}
+}
+// ----
+// TypeError: (78-100): Overriding function is missing 'override' specifier.

test/libsolidity/syntaxTests/inheritance/fallback_receive/receive_overrides_fallback.sol

@@ -0,0 +1,8 @@
+contract C {
+	fallback() external {}
+}
+contract D is C {
+	receive() override external payable {}
+}
+// ----
+// TypeError: (68-76): Function has override specified but does not override anything.

test/libsolidity/syntaxTests/inheritance/fallback_receive/receive_with_override.sol

@@ -0,0 +1,6 @@
+contract C {
+	receive() external payable {}
+}
+contract D is C {
+	receive() override external payable {}
+}

test/libsolidity/syntaxTests/inheritance/fallback_receive/receive_with_override_intermediate.sol

@@ -0,0 +1,8 @@
+contract C {
+	receive() external payable {}
+}
+contract D is C {
+}
+contract E is D {
+	receive() override external payable {}
+}

test/libsolidity/syntaxTests/inheritance/fallback_receive/receive_without_override.sol

@@ -0,0 +1,8 @@
+contract C {
+	receive() external payable {}
+}
+contract D is C {
+	receive() external payable {}
+}
+// ----
+// TypeError: (65-94): Overriding function is missing 'override' specifier.

test/libsolidity/syntaxTests/inheritance/fallback_receive/receive_without_override_intermediate.sol

@@ -0,0 +1,10 @@
+contract C {
+	receive() external payable {}
+}
+contract D is C {
+}
+contract E is D {
+	receive() external payable {}
+}
+// ----
+// TypeError: (85-114): Overriding function is missing 'override' specifier.

test/libsolidity/syntaxTests/inlineAssembly/storage_reference.sol

@@ -1,6 +1,6 @@
 contract C {
     uint[] x;
-    function() external {
+    fallback() external {
         uint[] storage y = x;
         assembly {
             pop(y)

test/libsolidity/syntaxTests/inlineAssembly/storage_reference_assignment.sol

@@ -1,6 +1,6 @@
 contract C {
     uint[] x;
-    function() external {
+    fallback() external {
         uint[] storage y = x;
         assembly {
             y_slot := 1

test/libsolidity/syntaxTests/inlineAssembly/storage_reference_fine.sol

@@ -1,6 +1,6 @@
 contract C {
     uint[] x;
-    function() external {
+    fallback() external {
         uint[] storage y = x;
         assembly {
             pop(y_slot)

test/libsolidity/syntaxTests/inlineAssembly/storage_reference_on_memory.sol

@@ -1,6 +1,6 @@
 contract C {
     uint[] x;
-    function() external {
+    fallback() external {
         uint[] memory y = x;
         assembly {
             pop(y_slot)

test/libsolidity/syntaxTests/nameAndTypeResolution/074_fallback_function.sol

@@ -1,4 +1,4 @@
 contract C {
     uint x;
-    function() external { x = 2; }
+    fallback() external { x = 2; }
 }

test/libsolidity/syntaxTests/nameAndTypeResolution/075_fallback_function_with_arguments.sol

@@ -1,6 +1,6 @@
 contract C {
     uint x;
-    function(uint a) external { x = 2; }
+    fallback(uint a) external { x = 2; }
 }
 // ----
 // TypeError: (37-45): Fallback function cannot take parameters.

test/libsolidity/syntaxTests/nameAndTypeResolution/076_fallback_function_in_library.sol

@@ -1,5 +1,5 @@
 library C {
-    function() external {}
+    fallback() external {}
 }
 // ----
 // TypeError: (16-38): Libraries cannot have fallback functions.

test/libsolidity/syntaxTests/nameAndTypeResolution/076_receive_function_in_library.sol

@@ -0,0 +1,6 @@
+library C {
+    receive() external payable {}
+}
+// ----
+// TypeError: (16-45): Library functions cannot be payable.
+// TypeError: (16-45): Libraries cannot have receive ether functions.

test/libsolidity/syntaxTests/nameAndTypeResolution/077_fallback_function_with_return_parameters.sol

@@ -1,5 +1,5 @@
 contract C {
-    function() external returns (uint) { }
+    fallback() external returns (uint) { }
 }
 // ----
-// TypeError: (45-51): Fallback function cannot return values.
+// TypeError: (45-51): Fallback function can only have a single "bytes memory" return value.

test/libsolidity/syntaxTests/nameAndTypeResolution/078_fallback_function_twice.sol

@@ -1,7 +1,7 @@
 contract C {
     uint x;
-    function() external { x = 2; }
-    function() external { x = 3; }
+    fallback() external { x = 2; }
+    fallback() external { x = 3; }
 }
 // ----
 // DeclarationError: (64-94): Only one fallback function is allowed.

test/libsolidity/syntaxTests/nameAndTypeResolution/079_fallback_function_inheritance.sol

@@ -1,7 +1,7 @@
 contract A {
     uint x;
-    function() external { x = 1; }
+    fallback() external { x = 1; }
 }
 contract C is A {
-    function() override external { x = 2; }
+    fallback() override external { x = 2; }
 }

test/libsolidity/syntaxTests/nameAndTypeResolution/196_integer_boolean_or.sol

@@ -1,3 +1,3 @@
-contract test { function() external { uint x = 1; uint y = 2; x || y; } }
+contract test { fallback() external { uint x = 1; uint y = 2; x || y; } }
 // ----
 // TypeError: (62-68): Operator || not compatible with types uint256 and uint256

test/libsolidity/syntaxTests/nameAndTypeResolution/197_integer_boolean_and.sol

@@ -1,3 +1,3 @@
-contract test { function() external { uint x = 1; uint y = 2; x && y; } }
+contract test { fallback() external { uint x = 1; uint y = 2; x && y; } }
 // ----
 // TypeError: (62-68): Operator && not compatible with types uint256 and uint256

test/libsolidity/syntaxTests/nameAndTypeResolution/198_integer_boolean_not.sol

@@ -1,3 +1,3 @@
-contract test { function() external { uint x = 1; !x; } }
+contract test { fallback() external { uint x = 1; !x; } }
 // ----
 // TypeError: (50-52): Unary operator ! cannot be applied to type uint256

test/libsolidity/syntaxTests/nameAndTypeResolution/199_integer_unsigned_exp_signed.sol

@@ -1,3 +1,3 @@
-contract test { function() external { uint x = 3; int y = -4; x ** y; } }
+contract test { fallback() external { uint x = 3; int y = -4; x ** y; } }
 // ----
 // TypeError: (62-68): Operator ** not compatible with types uint256 and int256. Exponentiation power is not allowed to be a signed integer type.

test/libsolidity/syntaxTests/nameAndTypeResolution/200_integer_signed_exp_unsigned.sol

@@ -1,5 +1,5 @@
 contract test {
-    function() external { uint x = 3; int y = -4; y ** x; }
+    fallback() external { uint x = 3; int y = -4; y ** x; }
     function f() public pure { int16 x = 3; uint8 y = 4; x ** y; }
     function g() public pure { int16 x = 3; uint16 y = 4; x ** y; }
 }

test/libsolidity/syntaxTests/nameAndTypeResolution/202_bytes_reference_compare_operators.sol

@@ -1,3 +1,3 @@
-contract test { bytes a; bytes b; function() external { a == b; } }
+contract test { bytes a; bytes b; fallback() external { a == b; } }
 // ----
 // TypeError: (56-62): Operator == not compatible with types bytes storage ref and bytes storage ref

test/libsolidity/syntaxTests/nameAndTypeResolution/203_struct_reference_compare_operators.sol

@@ -2,7 +2,7 @@ contract test {
   struct s {uint a;}
   s x;
   s y;
-  function() external {
+  fallback() external {
     x == y;
   }
 }

test/libsolidity/syntaxTests/nameAndTypeResolution/415_interface_functions.sol

@@ -1,5 +1,5 @@
 interface I {
-    function() external;
+    fallback() external;
     function f() external;
 }
 // ----

test/libsolidity/syntaxTests/nameAndTypeResolution/424_using_interface_complex.sol

@@ -2,7 +2,7 @@ interface I {
     event A();
     function f() external;
     function g() external;
-    function() external;
+    fallback() external;
 }
 contract C is I {
     function f() public override {

test/libsolidity/syntaxTests/nameAndTypeResolution/466_does_not_error_transfer_payable_fallback.sol

@@ -2,13 +2,13 @@
 // because A does not have a payable fallback function.
 
 contract A {
-    function() payable external {}
+    receive() payable external {}
 }
 
 contract B {
     A a;
 
-    function() external {
+    fallback() external {
         address(a).transfer(100);
     }
 }

test/libsolidity/syntaxTests/nameAndTypeResolution/467_does_not_error_transfer_regular_function.sol

@@ -5,7 +5,7 @@ contract A {
 contract B {
     A a;
 
-    function() external {
+    fallback() external {
         a.transfer();
     }
 }

test/libsolidity/syntaxTests/nameAndTypeResolution/526_fallback_marked_external.sol

@@ -1,3 +1,3 @@
 contract C {
-    function () external { }
+    fallback () external { }
 }

test/libsolidity/syntaxTests/nameAndTypeResolution/527_fallback_marked_internal.sol

@@ -1,5 +1,5 @@
 contract C {
-    function () internal { }
+    fallback () internal { }
 }
 // ----
 // TypeError: (17-41): Fallback function must be defined as "external".

test/libsolidity/syntaxTests/nameAndTypeResolution/528_fallback_marked_private.sol

@@ -1,5 +1,5 @@
 contract C {
-    function () private { }
+    fallback () private { }
 }
 // ----
 // TypeError: (17-40): Fallback function must be defined as "external".

test/libsolidity/syntaxTests/nameAndTypeResolution/529_fallback_marked_public.sol

@@ -1,5 +1,5 @@
 contract C {
-    function () public { }
+    fallback () public { }
 }
 // ----
 // TypeError: (17-39): Fallback function must be defined as "external".

test/libsolidity/syntaxTests/nameAndTypeResolution/535_address_overload_resolution.sol

@@ -6,7 +6,7 @@ contract C {
     function transfer(uint amount) public {
         address(this).transfer(amount); // to avoid pureness warning
     }
-    function() payable external {
+    receive() payable external {
     }
 }
 contract D {

test/libsolidity/syntaxTests/parsing/fallback_function.sol

@@ -1,4 +1,4 @@
 contract c {
-    function() external { }
+    fallback() external { }
 }
 // ----

test/libsolidity/syntaxTests/parsing/function_type_as_storage_variable_with_modifiers.sol

@@ -2,4 +2,4 @@ contract test {
 	function (uint, uint) modifier1() returns (uint) f1;
 }
 // ----
-// ParserError: (66-68): Expected '{' but got identifier
+// ParserError: (48-49): Expected ';' but got '('

test/libsolidity/syntaxTests/receiveEther/arguments.sol

@@ -0,0 +1,5 @@
+contract C {
+    receive(uint256) external payable {}
+}
+// ----
+// TypeError: (24-33): Receive ether function cannot take parameters.

test/libsolidity/syntaxTests/receiveEther/default_visibility.sol

@@ -0,0 +1,8 @@
+contract C {
+    // Check that visibility is also enforced for the receive ether function.
+    receive() {}
+}
+// ----
+// SyntaxError: (95-107): No visibility specified. Did you intend to add "external"?
+// TypeError: (95-107): Receive ether function must be payable, but is "nonpayable".
+// TypeError: (95-107): Receive ether function must be defined as "external".

test/libsolidity/syntaxTests/receiveEther/old_syntax.sol

@@ -0,0 +1,5 @@
+contract C {
+    function() external payable {}
+}
+// ----
+// ParserError: (45-46): Expected a state variable declaration. If you intended this as a fallback function or a function to handle plain ether transactions, use the "fallback" keyword or the "ether" keyword instead.

test/libsolidity/syntaxTests/receiveEther/pure_modifier.sol

@@ -0,0 +1,6 @@
+contract C {
+    uint x;
+    receive() external pure { x = 2; }
+}
+// ----
+// TypeError: (29-63): Receive ether function must be payable, but is "pure".

test/libsolidity/syntaxTests/receiveEther/receive_as_function_name.sol

@@ -0,0 +1,5 @@
+contract C {
+    function receive() external pure {}
+}
+// ----
+// Warning: (26-33): This function is named "receive" but is not the receive function of the contract. If you intend this to be a receive function, use "receive(...) { ... }" without the "function" keyword to define it.

test/libsolidity/syntaxTests/receiveEther/return_value.sol

@@ -0,0 +1,6 @@
+contract C {
+    receive() external returns (uint256) {}
+}
+// ----
+// TypeError: (17-56): Receive ether function must be payable, but is "nonpayable".
+// TypeError: (44-53): Receive ether function cannot return values.

test/libsolidity/syntaxTests/receiveEther/view_modifier.sol

@@ -0,0 +1,6 @@
+contract C {
+    uint x;
+    receive() external view { x = 2; }
+}
+// ----
+// TypeError: (29-63): Receive ether function must be payable, but is "view".

test/libsolidity/syntaxTests/types/address/address_in_struct_fine.sol

@@ -15,6 +15,6 @@ contract B {
     function f() public {
         s.a = address(this);
     }
-    function() external payable {
+    receive() external payable {
     }
 }

test/libsolidity/syntaxTests/types/address/address_to_contract_payable_fallback.sol

@@ -2,7 +2,8 @@ contract C {
   function f() public pure returns (C c) {
     c = C(address(2));
   }
-  function() external payable {
+  fallback() external payable {
   }
 }
 // ----
+// Warning: (0-120): This contract has a payable fallback function, but no receive ether function. Consider adding a receive ether function.

test/libsolidity/syntaxTests/types/address/address_to_contract_receive.sol

@@ -0,0 +1,8 @@
+contract C {
+  function f() public pure returns (C c) {
+    c = C(address(2));
+  }
+  receive() external payable {
+  }
+}
+// ----

test/libsolidity/syntaxTests/types/address/contract_non_payable_fallback_to_payable_address.sol

@@ -3,7 +3,7 @@ contract C {
     address payable a = address(this);
     a;
   }
-  function() external {
+  fallback() external {
   }
 }
 // ----

test/libsolidity/syntaxTests/types/address/contract_payable_fallback_to_payable_address.sol

@@ -3,7 +3,8 @@ contract C {
     address payable a = address(this);
     a;
   }
-  function() external payable {
+  fallback() external payable {
   }
 }
 // ----
+// Warning: (0-129): This contract has a payable fallback function, but no receive ether function. Consider adding a receive ether function.

test/libsolidity/syntaxTests/types/address/contract_payable_fallback_to_payable_address_implicitly.sol

@@ -3,8 +3,9 @@ contract C {
     address payable a = this;
     a;
   }
-  function() external payable {
+  fallback() external payable {
   }
 }
 // ----
+// Warning: (0-120): This contract has a payable fallback function, but no receive ether function. Consider adding a receive ether function.
 // TypeError: (46-70): Type contract C is not implicitly convertible to expected type address payable.

test/libsolidity/syntaxTests/types/address/contract_receive_to_payable_address.sol

@@ -0,0 +1,9 @@
+contract C {
+  function f() public view {
+    address payable a = address(this);
+    a;
+  }
+  receive() external payable {
+  }
+}
+// ----

test/libsolidity/syntaxTests/types/address/contract_receive_to_payable_address_implicitly.sol

@@ -0,0 +1,10 @@
+contract C {
+  function f() public view {
+    address payable a = this;
+    a;
+  }
+  receive() external payable {
+  }
+}
+// ----
+// TypeError: (46-70): Type contract C is not implicitly convertible to expected type address payable.

test/libsolidity/syntaxTests/types/address/nonpayable_address_to_contract_payable_fallback.sol

@@ -3,8 +3,9 @@ contract C {
     address a = address(2);
     c = C(a);
   }
-  function() external payable {
+  fallback() external payable {
   }
 }
 // ----
+// Warning: (0-139): This contract has a payable fallback function, but no receive ether function. Consider adding a receive ether function.
 // TypeError: (92-96): Explicit type conversion not allowed from non-payable "address" to "contract C", which has a payable fallback function.

test/libsolidity/syntaxTests/types/address/nonpayable_address_to_contract_receive.sol

@@ -0,0 +1,10 @@
+contract C {
+  function f() public pure returns (C c) {
+    address a = address(2);
+    c = C(a);
+  }
+  receive() external payable {
+  }
+}
+// ----
+// TypeError: (92-96): Explicit type conversion not allowed from non-payable "address" to "contract C", which has a payable fallback function.

test/libsolidity/syntaxTests/types/var_decl_val_mismatch.sol

@@ -1,6 +1,6 @@
 contract n
 {
-	function()
+	fallback()
 	{
 		// Used to cause a segfault
 		var (x,y) = (1);
@@ -13,5 +13,4 @@ contract n
 }
 // ----
 // SyntaxError: (14-129): No visibility specified. Did you intend to add "external"?
-// TypeError: (14-129): Fallback function must be defined as "external".
 // TypeError: (60-75): Different number of components on the left hand side (2) than on the right hand side (1).

test/libsolidity/syntaxTests/viewPureChecker/builtin_functions.sol

@@ -16,5 +16,5 @@ contract C {
         assert(true);
         x; y; z;
     }
-    function() payable external {}
+    receive() payable external {}
 }

test/libsolidity/syntaxTests/viewPureChecker/builtin_functions_view_fail.sol

@@ -16,7 +16,7 @@ contract C {
         (bool success,) = address(this).call("");
         require(success);
     }
-    function() payable external {
+    receive() payable external {
     }
 }
 // ----

test/libsolidity/syntaxTests/viewPureChecker/callvalue_nonpayable_assembly_fallback.sol

@@ -1,6 +1,6 @@
 contract C
 {
-    function () external {
+    fallback() external {
         uint x;
         assembly {
             x := callvalue()

test/libsolidity/syntaxTests/viewPureChecker/callvalue_payable_assembly_fallback.sol

@@ -1,6 +1,8 @@
 contract C
 {
-    function () external payable {
+    receive () external payable {
+    }
+    fallback () external payable {
         uint x;
         assembly {
             x := callvalue()