Merge pull request #10255 from ethereum/this-super-underscore-reserved-identifiers

[BREAKING] Disallow declarations with name "this", "super" and "_"

Changelog.md

@@ -13,6 +13,7 @@ Breaking Changes:
  * Code Generator: Use ``revert`` with error signature ``Panic(uint256)`` and error codes instead of invalid opcode on failing assertions.
  * Type System: Explicit conversions from literals to integer type is as strict as implicit conversions.
  * Type System: Explicit conversions from literals to enums are only allowed if the value fits in the enum.
+ * Type System: Declarations with the name ``this``, ``super`` and ``_`` are disallowed, with the exception of public functions and events.
 
 Language Features:
  * Super constructors can now be called using the member notation e.g. ``M.C(123)``.

docs/080-breaking-changes.rst

@@ -58,3 +58,6 @@ New Restrictions
 * ``enum`` definitions cannot contain more than 256 members.
 
   This will make it safe to assume that the underlying type in the ABI is always ``uint8``.
+
+* Declarations with the name ``this``, ``super`` and ``_`` are disallowed, with the exception of
+  public functions and events.

libsolidity/analysis/NameAndTypeResolver.cpp

@@ -509,6 +509,33 @@ bool DeclarationRegistrationHelper::registerDeclaration(
 	// We use "invisible" for both inactive variables in blocks and for members invisible in contracts.
 	// They cannot both be true at the same time.
 	solAssert(!(_inactive && !_declaration.isVisibleInContract()), "");
+
+	static set<string> illegalNames{"_", "super", "this"};
+
+	if (illegalNames.count(name))
+	{
+		auto isPublicFunctionOrEvent = [](Declaration const* _d) -> bool
+		{
+			if (auto functionDefinition = dynamic_cast<FunctionDefinition const*>(_d))
+			{
+				if (!functionDefinition->isFree() && functionDefinition->isPublic())
+					return true;
+			}
+			else if (dynamic_cast<EventDefinition const*>(_d))
+				return true;
+
+			return false;
+		};
+
+		// We allow an exception for public functions or events.
+		if (!isPublicFunctionOrEvent(&_declaration))
+			_errorReporter.declarationError(
+				3726_error,
+				*_errorLocation,
+				"The name \"" + name + "\" is reserved."
+			);
+	}
+
 	if (!_container.registerDeclaration(_declaration, _name, _errorLocation, !_declaration.isVisibleInContract() || _inactive, false))
 	{
 		SourceLocation firstDeclarationLocation;

libsolidity/analysis/ReferencesResolver.cpp

@@ -380,4 +380,11 @@ void ReferencesResolver::validateYulIdentifierName(yul::YulString _name, SourceL
 			_location,
 			"User-defined identifiers in inline assembly cannot contain '.'."
 		);
+
+	if (set<string>{"this", "super", "_"}.count(_name.str()))
+		m_errorReporter.declarationError(
+			4113_error,
+			_location,
+			"The identifier name \"" + _name.str() + "\" is reserved."
+		);
 }

test/libsolidity/semanticTests/underscore/in_function.sol

@@ -1,17 +0,0 @@
-contract C {
-    function f() public pure returns (uint) {
-        uint _;
-        return _;
-    }
-
-    function g() public pure returns (uint) {
-        uint _ = 1;
-        return _;
-    }
-}
-// ====
-// compileViaYul: also
-// compileToEwasm: also
-// ----
-// f() -> 0
-// g() -> 1

test/libsolidity/semanticTests/underscore/in_modifier.sol

@@ -1,23 +0,0 @@
-contract C {
-    modifier m() {
-        _;
-    }
-
-    modifier n() {
-        string memory _ = "failed";
-        _;
-        revert(_);
-    }
-
-    function f() m() public returns (uint) {
-        return 88;
-    }
-
-    function g() n() public returns (uint) {
-    }
-}
-// ====
-// EVMVersion: >=byzantium
-// ----
-// f() -> 88
-// g() -> FAILURE, hex"08c379a0", 0x20, 6, "failed"

test/libsolidity/smtCheckerTests/functions/this_fake.sol

@@ -1,24 +0,0 @@
-pragma experimental SMTChecker;
-
-contract C
-{
-    uint public x;
-    C c;
-    function f(C _c) public {
-        c = _c;
-    }
-    function g() public {
-        C this = c;
-		x = 0;
-        this.h();
-		// State knowledge is erased.
-		// Function call is not inlined.
-		assert(x == 0);
-    }
-    function h() public {
-        x = 2;
-    }
-}
-// ----
-// Warning 2319: (160-166): This declaration shadows a builtin symbol.
-// Warning 6328: (268-282): CHC: Assertion violation happens here.

test/libsolidity/syntaxTests/duplicateFunctions/illegal_names_exception.sol

@@ -0,0 +1,12 @@
+// Exception for the rule about illegal names.
+contract C {
+	function this() public {
+	}
+	function super() public {
+	}
+	function _() public {
+	}
+}
+// ----
+// Warning 2319: (61-88): This declaration shadows a builtin symbol.
+// Warning 2319: (90-118): This declaration shadows a builtin symbol.

test/libsolidity/syntaxTests/duplicateFunctions/illegal_names_functions.sol

@@ -0,0 +1,17 @@
+contract C {
+    function _() internal returns(uint) {
+        return 1;
+    }
+
+    function super() internal {
+    }
+
+    function this() internal {
+    }
+}
+// ----
+// DeclarationError 3726: (17-78): The name "_" is reserved.
+// DeclarationError 3726: (84-117): The name "super" is reserved.
+// DeclarationError 3726: (123-155): The name "this" is reserved.
+// Warning 2319: (84-117): This declaration shadows a builtin symbol.
+// Warning 2319: (123-155): This declaration shadows a builtin symbol.

test/libsolidity/syntaxTests/enums/illegal_names.sol

@@ -0,0 +1,31 @@
+enum this {
+    a
+}
+enum super {
+    b
+}
+enum _ {
+    c
+}
+
+enum E {
+    this,
+    super,
+    _
+}
+
+contract C {
+    this a;
+    super b;
+    _ c;
+    E e;
+}
+// ----
+// DeclarationError 3726: (0-19): The name "this" is reserved.
+// DeclarationError 3726: (20-40): The name "super" is reserved.
+// DeclarationError 3726: (41-57): The name "_" is reserved.
+// DeclarationError 3726: (72-76): The name "this" is reserved.
+// DeclarationError 3726: (82-87): The name "super" is reserved.
+// DeclarationError 3726: (93-94): The name "_" is reserved.
+// Warning 2319: (0-19): This declaration shadows a builtin symbol.
+// Warning 2319: (20-40): This declaration shadows a builtin symbol.

test/libsolidity/syntaxTests/events/illegal_names_exception.sol

@@ -0,0 +1,9 @@
+// Exception for the illegal name list. External interface events
+contract C {
+	event this();
+	event super();
+	event _();
+}
+// ----
+// Warning 2319: (80-93): This declaration shadows a builtin symbol.
+// Warning 2319: (95-109): This declaration shadows a builtin symbol.

test/libsolidity/syntaxTests/freeFunctions/illegal_names.sol

@@ -0,0 +1,17 @@
+function this() {}
+function super() {}
+function _() {}
+
+contract C {
+	function test() public {
+		this();
+		super();
+		_();
+	}
+}
+// ----
+// DeclarationError 3726: (0-18): The name "this" is reserved.
+// DeclarationError 3726: (19-38): The name "super" is reserved.
+// DeclarationError 3726: (39-54): The name "_" is reserved.
+// Warning 2319: (0-18): This declaration shadows a builtin symbol.
+// Warning 2319: (19-38): This declaration shadows a builtin symbol.

test/libsolidity/syntaxTests/immutable/illegal_names.sol

@@ -0,0 +1,11 @@
+contract C {
+    uint immutable super;
+    uint immutable _;
+    uint immutable this;
+}
+// ----
+// DeclarationError 3726: (17-37): The name "super" is reserved.
+// DeclarationError 3726: (43-59): The name "_" is reserved.
+// DeclarationError 3726: (65-84): The name "this" is reserved.
+// Warning 2319: (17-37): This declaration shadows a builtin symbol.
+// Warning 2319: (65-84): This declaration shadows a builtin symbol.

test/libsolidity/syntaxTests/inlineAssembly/invalid/illegal_names.sol

@@ -0,0 +1,55 @@
+contract C {
+    function f() public {
+        // reserved function names
+        assembly {
+            function this() {
+            }
+            function super() {
+            }
+            function _() {
+            }
+        }
+
+        // reserved names as function argument
+        assembly {
+            function a(this) {
+            }
+            function b(super) {
+            }
+            function c(_) {
+            }
+        }
+
+        // reserved names as function return parameter
+        assembly {
+            function d() -> this {
+            }
+            function g() -> super {
+            }
+            function c() -> _ {
+            }
+        }
+
+        // reserved names as variable declaration
+        assembly {
+            let this := 1
+            let super := 1
+            let _ := 1
+        }
+    }
+}
+// ----
+// DeclarationError 4113: (105-136): The identifier name "this" is reserved.
+// DeclarationError 4113: (149-181): The identifier name "super" is reserved.
+// DeclarationError 4113: (194-222): The identifier name "_" is reserved.
+// DeclarationError 4113: (323-327): The identifier name "this" is reserved.
+// DeclarationError 4113: (368-373): The identifier name "super" is reserved.
+// DeclarationError 4113: (414-415): The identifier name "_" is reserved.
+// DeclarationError 4113: (546-550): The identifier name "this" is reserved.
+// DeclarationError 4113: (595-600): The identifier name "super" is reserved.
+// DeclarationError 4113: (645-646): The identifier name "_" is reserved.
+// DeclarationError 4113: (759-763): The identifier name "this" is reserved.
+// DeclarationError 3859: (759-763): This declaration shadows a declaration outside the inline assembly block.
+// DeclarationError 4113: (785-790): The identifier name "super" is reserved.
+// DeclarationError 3859: (785-790): This declaration shadows a declaration outside the inline assembly block.
+// DeclarationError 4113: (812-813): The identifier name "_" is reserved.

test/libsolidity/syntaxTests/modifiers/illegal_name.sol

@@ -0,0 +1,11 @@
+contract C {
+	modifier this { _; }
+	modifier super { _; }
+	modifier _ { _; }
+}
+// ----
+// DeclarationError 3726: (14-34): The name "this" is reserved.
+// DeclarationError 3726: (36-57): The name "super" is reserved.
+// DeclarationError 3726: (59-76): The name "_" is reserved.
+// Warning 2319: (14-34): This declaration shadows a builtin symbol.
+// Warning 2319: (36-57): This declaration shadows a builtin symbol.

test/libsolidity/syntaxTests/nameAndTypeResolution/shadowsBuiltin/illegal_names_assembly_functions.sol

@@ -0,0 +1,16 @@
+contract C {
+    function f() public pure {
+        assembly {
+            function this() {
+            }
+            function super() {
+            }
+            function _() {
+            }
+        }
+    }
+}
+// ----
+// DeclarationError 4113: (75-106): The identifier name "this" is reserved.
+// DeclarationError 4113: (119-151): The identifier name "super" is reserved.
+// DeclarationError 4113: (164-192): The identifier name "_" is reserved.

test/libsolidity/syntaxTests/nameAndTypeResolution/shadowsBuiltin/illegal_names_assembly_identifier.sol

@@ -0,0 +1,15 @@
+contract C {
+    function f() public {
+        assembly {
+            let super := 1
+            let this := 1
+            let _ := 1
+        }
+    }
+}
+// ----
+// DeclarationError 4113: (74-79): The identifier name "super" is reserved.
+// DeclarationError 3859: (74-79): This declaration shadows a declaration outside the inline assembly block.
+// DeclarationError 4113: (101-105): The identifier name "this" is reserved.
+// DeclarationError 3859: (101-105): This declaration shadows a declaration outside the inline assembly block.
+// DeclarationError 4113: (127-128): The identifier name "_" is reserved.

test/libsolidity/syntaxTests/nameAndTypeResolution/shadowsBuiltin/illegal_names_function_parameters.sol

@@ -0,0 +1,28 @@
+contract C {
+    function f(uint super) public {
+    }
+    function g(uint this) public {
+    }
+    function h(uint _) public {
+    }
+    function i() public returns (uint super) {
+        return 1;
+    }
+    function j() public returns (uint this) {
+        return 1;
+    }
+    function k() public returns (uint _) {
+        return 1;
+    }
+}
+// ----
+// DeclarationError 3726: (28-38): The name "super" is reserved.
+// DeclarationError 3726: (70-79): The name "this" is reserved.
+// DeclarationError 3726: (111-117): The name "_" is reserved.
+// DeclarationError 3726: (167-177): The name "super" is reserved.
+// DeclarationError 3726: (238-247): The name "this" is reserved.
+// DeclarationError 3726: (308-314): The name "_" is reserved.
+// Warning 2319: (28-38): This declaration shadows a builtin symbol.
+// Warning 2319: (70-79): This declaration shadows a builtin symbol.
+// Warning 2319: (167-177): This declaration shadows a builtin symbol.
+// Warning 2319: (238-247): This declaration shadows a builtin symbol.

test/libsolidity/syntaxTests/nameAndTypeResolution/shadowsBuiltin/illegal_names_library_using_for.sol

@@ -0,0 +1,26 @@
+library super {
+    function f() public {
+    }
+}
+
+library this {
+    function f() public {
+    }
+}
+library _ {
+    function f() public {
+    }
+}
+
+contract C {
+    // These are not errors
+    using super for uint;
+    using this for uint16;
+    using _ for int;
+}
+// ----
+// DeclarationError 3726: (0-49): The name "super" is reserved.
+// DeclarationError 3726: (51-99): The name "this" is reserved.
+// DeclarationError 3726: (100-145): The name "_" is reserved.
+// Warning 2319: (0-49): This declaration shadows a builtin symbol.
+// Warning 2319: (51-99): This declaration shadows a builtin symbol.

test/libsolidity/syntaxTests/nameAndTypeResolution/shadowsBuiltin/illegal_names_using_for.sol

@@ -0,0 +1,32 @@
+library L {
+    function f() public {
+    }
+}
+
+// error
+struct super {
+    uint a;
+}
+
+// error
+struct this {
+    uint a;
+}
+
+// error
+struct _ {
+    uint a;
+}
+
+contract C {
+    // These are not errors
+    using L for super;
+    using L for _;
+    using L for this;
+}
+// ----
+// DeclarationError 3726: (56-84): The name "super" is reserved.
+// DeclarationError 3726: (95-122): The name "this" is reserved.
+// DeclarationError 3726: (133-157): The name "_" is reserved.
+// Warning 2319: (56-84): This declaration shadows a builtin symbol.
+// Warning 2319: (95-122): This declaration shadows a builtin symbol.

test/libsolidity/syntaxTests/nameAndTypeResolution/shadowsBuiltin/this_super.sol

@@ -5,7 +5,7 @@ contract C {
     }
 }
 // ----
+// DeclarationError 3726: (52-62): The name "super" is reserved.
+// DeclarationError 3726: (76-85): The name "this" is reserved.
 // Warning 2319: (52-62): This declaration shadows a builtin symbol.
 // Warning 2319: (76-85): This declaration shadows a builtin symbol.
-// Warning 2072: (52-62): Unused local variable.
-// Warning 2072: (76-85): Unused local variable.

test/libsolidity/syntaxTests/parsing/placeholder_in_function_context.sol

@@ -5,4 +5,4 @@ contract c {
     }
 }
 // ----
-// Warning 2018: (17-105): Function state mutability can be restricted to pure
+// DeclarationError 3726: (66-72): The name "_" is reserved.

test/libsolidity/syntaxTests/structs/illegal_names.sol

@@ -0,0 +1,15 @@
+struct this { uint a; }
+struct super { uint b; }
+struct _ { uint c; }
+
+contract C {
+	this a;
+	super b;
+	_ c;
+}
+// ----
+// DeclarationError 3726: (0-23): The name "this" is reserved.
+// DeclarationError 3726: (24-48): The name "super" is reserved.
+// DeclarationError 3726: (49-69): The name "_" is reserved.
+// Warning 2319: (0-23): This declaration shadows a builtin symbol.
+// Warning 2319: (24-48): This declaration shadows a builtin symbol.

test/libsolidity/syntaxTests/underscore/as_function.sol

@@ -10,3 +10,4 @@ contract C {
         _;
     }
 }
+// ----

test/libsolidity/syntaxTests/underscore/in_function.sol

@@ -14,4 +14,6 @@ contract C {
     }
 }
 // ----
+// DeclarationError 3726: (67-73): The name "_" is reserved.
+// DeclarationError 3726: (154-160): The name "_" is reserved.
 // DeclarationError 7576: (230-231): Undeclared identifier.

test/libsolidity/syntaxTests/underscore/in_modifier.sol

@@ -16,3 +16,4 @@ contract C {
     }
 }
 // ----
+// DeclarationError 3726: (77-92): The name "_" is reserved.

test/libsolidity/syntaxTests/variableDeclaration/illegal_names.sol

@@ -0,0 +1,30 @@
+uint constant this = 1;
+uint constant super = 2;
+uint constant _ = 3;
+contract C {
+	address this;
+	int super;
+	mapping (address => address) _;
+}
+
+contract D {
+	address[] this;
+	struct _ { uint super; }
+}
+// ----
+// DeclarationError 3726: (0-22): The name "this" is reserved.
+// DeclarationError 3726: (24-47): The name "super" is reserved.
+// DeclarationError 3726: (49-68): The name "_" is reserved.
+// DeclarationError 3726: (84-96): The name "this" is reserved.
+// DeclarationError 3726: (99-108): The name "super" is reserved.
+// DeclarationError 3726: (111-141): The name "_" is reserved.
+// DeclarationError 3726: (160-174): The name "this" is reserved.
+// DeclarationError 3726: (177-201): The name "_" is reserved.
+// DeclarationError 3726: (188-198): The name "super" is reserved.
+// Warning 2519: (84-96): This declaration shadows an existing declaration.
+// Warning 2519: (99-108): This declaration shadows an existing declaration.
+// Warning 2519: (111-141): This declaration shadows an existing declaration.
+// Warning 2519: (160-174): This declaration shadows an existing declaration.
+// Warning 2519: (177-201): This declaration shadows an existing declaration.
+// Warning 2319: (0-22): This declaration shadows a builtin symbol.
+// Warning 2319: (24-47): This declaration shadows a builtin symbol.