Implement override checking

test/libsolidity/syntaxTests/inheritance/override/add_view.sol

@@ -1,4 +1,5 @@
 contract B { function f() public {} }
 contract C is B { function f() public view {} }
 // ----
+// TypeError: (56-83): Overriding function is missing 'override' specifier.
 // TypeError: (56-83): Overriding function changes state mutability from "nonpayable" to "view".

test/libsolidity/syntaxTests/inheritance/override/calldata_memory.sol

@@ -6,8 +6,8 @@ contract A {
     function i(uint[] calldata) external payable {}
 }
 contract B is A {
-    function f(uint[] memory) public pure {}
-    function g(uint[] memory) public view { dummy; }
-    function h(uint[] memory) public { dummy = 42; }
-    function i(uint[] memory) public payable {}
+    function f(uint[] memory) public override pure {}
+    function g(uint[] memory) public override view { dummy; }
+    function h(uint[] memory) public override { dummy = 42; }
+    function i(uint[] memory) public override payable {}
 }

test/libsolidity/syntaxTests/inheritance/override/calldata_memory_conflict.sol

@@ -6,21 +6,17 @@ contract A {
     function i(uint[] calldata) external payable {}
 }
 contract B is A {
-    function f(uint[] calldata) external pure {}
-    function g(uint[] calldata) external view { dummy; }
-    function h(uint[] calldata) external { dummy = 42; }
-    function i(uint[] calldata) external payable {}
-    function f(uint[] memory) public pure {}
-    function g(uint[] memory) public view { dummy; }
-    function h(uint[] memory) public { dummy = 42; }
-    function i(uint[] memory) public payable {}
+    function f(uint[] calldata) external override pure {}
+    function g(uint[] calldata) external override view { dummy; }
+    function h(uint[] calldata) external override { dummy = 42; }
+    function i(uint[] calldata) external override payable {}
+    function f(uint[] memory) public override pure {}
+    function g(uint[] memory) public override view { dummy; }
+    function h(uint[] memory) public override { dummy = 42; }
+    function i(uint[] memory) public override payable {}
 }
 // ----
-// DeclarationError: (268-312): Function with same name and arguments defined twice.
-// DeclarationError: (317-369): Function with same name and arguments defined twice.
-// DeclarationError: (374-426): Function with same name and arguments defined twice.
-// DeclarationError: (431-478): Function with same name and arguments defined twice.
-// TypeError: (268-312): Overriding function visibility differs.
-// TypeError: (317-369): Overriding function visibility differs.
-// TypeError: (374-426): Overriding function visibility differs.
-// TypeError: (431-478): Overriding function visibility differs.
+// DeclarationError: (268-321): Function with same name and arguments defined twice.
+// DeclarationError: (326-387): Function with same name and arguments defined twice.
+// DeclarationError: (392-453): Function with same name and arguments defined twice.
+// DeclarationError: (458-514): Function with same name and arguments defined twice.

test/libsolidity/syntaxTests/inheritance/override/calldata_memory_interface.sol

@@ -6,8 +6,8 @@ interface I {
 }
 contract C is I {
     uint dummy;
-    function f(uint[] memory) public pure {}
-    function g(uint[] memory) public view { dummy; }
-    function h(uint[] memory) public { dummy = 42; }
-    function i(uint[] memory) public payable {}
+    function f(uint[] memory) public override pure {}
+    function g(uint[] memory) public override view { dummy; }
+    function h(uint[] memory) public override { dummy = 42; }
+    function i(uint[] memory) public override payable {}
 }

test/libsolidity/syntaxTests/inheritance/override/calldata_memory_interface_instantiate.sol

@@ -2,11 +2,11 @@ interface I {
     function f(uint[] calldata) external pure;
 }
 contract A is I {
-    function f(uint[] memory) public pure {}
+    function f(uint[] memory) public override pure {}
 }
 contract C {
     function f() public {
         I i = I(new A());
         i.f(new uint[](1));
     }
-}
+}

test/libsolidity/syntaxTests/inheritance/override/calldata_memory_interface_struct.sol

@@ -8,10 +8,10 @@ interface I {
 }
 contract C is I {
     uint dummy;
-    function f(S memory) public pure {}
-    function g(S memory) public view { dummy; }
-    function h(S memory) public { dummy = 42; }
-    function i(S memory) public payable {}
+    function f(S memory) public override pure {}
+    function g(S memory) public override view { dummy; }
+    function h(S memory) public override { dummy = 42; }
+    function i(S memory) public override payable {}
 }
 // ----
 // Warning: (0-33): Experimental features are turned on. Do not use experimental features on live deployments.

test/libsolidity/syntaxTests/inheritance/override/calldata_memory_struct.sol

@@ -8,10 +8,10 @@ contract A {
     function i(S calldata) external payable {}
 }
 contract B is A {
-    function f(S memory) public pure {}
-    function g(S memory) public view { dummy; }
-    function h(S memory) public { dummy = 42; }
-    function i(S memory) public payable {}
+    function f(S memory) public override pure {}
+    function g(S memory) public override view { dummy; }
+    function h(S memory) public override { dummy = 42; }
+    function i(S memory) public override payable {}
 }
 // ----
 // Warning: (0-33): Experimental features are turned on. Do not use experimental features on live deployments.

test/libsolidity/syntaxTests/inheritance/override/change_return_types_in_interface.sol

@@ -7,4 +7,5 @@ contract B is I {
   function f() public pure returns (uint, uint) {}
 }
 // ----
+// TypeError: (182-230): Overriding function is missing 'override' specifier.
 // TypeError: (182-230): Overriding function return types differ.

test/libsolidity/syntaxTests/inheritance/override/external_turns_public_no_params.sol

@@ -2,6 +2,6 @@ contract A {
     function f() external pure {}
 }
 contract B is A {
-    function f() public pure {
+    function f() public override pure {
     }
 }

test/libsolidity/syntaxTests/inheritance/override/internal_external.sol

@@ -4,4 +4,3 @@ contract A {
 }
 // ----
 // DeclarationError: (17-61): Function with same name and arguments defined twice.
-// TypeError: (17-61): Overriding function visibility differs.

test/libsolidity/syntaxTests/inheritance/override/internal_external_inheritance.sol

@@ -6,4 +6,4 @@ contract B {
 }
 contract C is A, B {}
 // ----
-// TypeError: (81-123): Overriding function visibility differs.
+// TypeError: (126-147): Derived contract must override function "f". Function with the same name and parameter types defined in two or more base classes.

test/libsolidity/syntaxTests/inheritance/override/override.sol

@@ -1,5 +1,11 @@
-contract X {
+contract A {
+	int public testvar;
+	function test() internal returns (uint256);
+	function test2() internal returns (uint256);
+}
+contract X is A {
 	int public override testvar;
 	function test() internal override returns (uint256);
+	function test2() internal override(A) returns (uint256);
 }
 // ----

test/libsolidity/syntaxTests/inheritance/override/override_ambiguous.sol

@@ -0,0 +1,14 @@
+contract A {
+	int public testvar;
+	function foo() internal returns (uint256);
+}
+contract B {
+	function foo() internal returns (uint256);
+	function test() internal returns (uint256);
+}
+contract X is A, B {
+	int public override testvar;
+	function test() internal override returns (uint256);
+}
+// ----
+// TypeError: (184-290): Derived contract must override function "foo". Function with the same name and parameter types defined in two or more base classes.

test/libsolidity/syntaxTests/inheritance/override/override_base_base.sol

@@ -0,0 +1,20 @@
+contract A {
+	function foo() internal returns (uint256);
+}
+
+contract B is A {
+	function foo() internal override returns (uint256);
+}
+
+contract C is B {
+	function foo() internal override returns (uint256);
+}
+
+contract D is C {
+	function foo() internal override returns (uint256);
+}
+
+contract X is D {
+	function foo() internal override returns (uint256);
+}
+// ----

test/libsolidity/syntaxTests/inheritance/override/override_multiple.sol

@@ -1,9 +1,21 @@
 contract A {
+	int public testvar;
+	function foo() internal returns (uint256);
+	function test(uint8 _a) internal returns (uint256);
+}
+contract B {
+	function foo() internal returns (uint256);
+	function test() internal returns (uint256);
+}
+contract C {
 	function foo() internal returns (uint256);
 }
-contract X {
+contract D {
+	function foo() internal returns (uint256);
+}
+contract X is A, B, C, D {
 	int public override testvar;
 	function test() internal override returns (uint256);
-	function foo() internal override(X, A) returns (uint256);
+	function foo() internal override(A, B, C, D) returns (uint256);
 }
 // ----

test/libsolidity/syntaxTests/inheritance/override/override_multiple2.sol

@@ -0,0 +1,15 @@
+contract A {
+	int public testvar;
+	function foo() internal returns (uint256);
+	function test(uint8 _a) internal returns (uint256);
+}
+contract B {
+	function foo() internal returns (uint256);
+}
+
+contract C is A {
+}
+contract D is A, B, C {
+	function foo() internal override(A, B) returns (uint256);
+}
+// ----

test/libsolidity/syntaxTests/inheritance/override/override_multiple_duplicated.sol

@@ -0,0 +1,26 @@
+contract A {
+	int public testvar;
+	function foo() internal returns (uint256);
+	function test(uint8 _a) internal returns (uint256);
+}
+contract B {
+	function foo() internal returns (uint256);
+	function test() internal returns (uint256);
+}
+contract C {
+	function foo() internal returns (uint256);
+}
+contract D {
+	function foo() internal returns (uint256);
+	function test() internal returns (uint256);
+}
+contract X is A, B, C, D {
+	int public override testvar;
+	function test() internal override(B, D, D) returns (uint256);
+	function foo() internal override(A, C, B, B, B, D ,D) returns (uint256);
+}
+// ----
+// TypeError: (498-499): Duplicate contract "D" found in override list of "test".
+// TypeError: (563-564): Duplicate contract "B" found in override list of "foo".
+// TypeError: (566-567): Duplicate contract "B" found in override list of "foo".
+// TypeError: (572-573): Duplicate contract "D" found in override list of "foo".

test/libsolidity/syntaxTests/inheritance/override/override_multiple_missing.sol

@@ -0,0 +1,24 @@
+contract A {
+	int public testvar;
+	function foo() internal returns (uint256);
+	function test(uint8 _a) internal returns (uint256);
+}
+contract B {
+	function foo() internal returns (uint256);
+	function test() internal returns (uint256);
+}
+contract C {
+	function foo() internal returns (uint256);
+}
+contract D {
+	function foo() internal returns (uint256);
+	function test() internal returns (uint256);
+}
+contract X is A, B, C, D {
+	int public override testvar;
+	function test() internal override(B, D, C) returns (uint256);
+	function foo() internal override(A, C) returns (uint256);
+}
+// ----
+// TypeError: (483-500): Invalid contract specified in override list: C.
+// TypeError: (545-559): Function needs to specify overridden contracts B and D.

test/libsolidity/syntaxTests/inheritance/override/override_multiple_unresolved.sol

@@ -0,0 +1,6 @@
+contract A {
+	int public testvar;
+	function foo() internal override(N, Z) returns (uint256);
+}
+// ----
+// DeclarationError: (68-69): Identifier not found or not unique.

test/libsolidity/syntaxTests/inheritance/override/override_return_mismatch.sol

@@ -0,0 +1,14 @@
+contract A {
+	int public testvar;
+	function foo() internal returns (uint256);
+}
+contract B {
+	function foo() internal returns (uint8);
+	function test() internal returns (uint256);
+}
+contract X is A, B {
+	int public override testvar;
+	function test() internal override returns (uint256);
+}
+// ----
+// TypeError: (182-288): Derived contract must override function "foo". Function with the same name and parameter types defined in two or more base classes.

test/libsolidity/syntaxTests/inheritance/override/override_shared_base.sol

@@ -0,0 +1,15 @@
+contract I {
+	function set() public {}
+}
+contract A is I {
+	uint a;
+	function set() public override { a = 1; super.set(); a = 2; }
+}
+contract B is I {
+	uint b;
+	function set() public override { b = 1; super.set(); b = 2; }
+
+}
+contract X is A, B {
+	function set() public override(A, B) { super.set(); }
+}

test/libsolidity/syntaxTests/inheritance/override/override_shared_base_partial.sol

@@ -0,0 +1,10 @@
+contract I {
+  function f() external {}
+}
+contract A is I {
+  function f() external override {}
+}
+contract B is I {}
+contract C is A, B {
+  function f() external override(A, I) {}
+}

test/libsolidity/syntaxTests/inheritance/override/override_shared_base_simple.sol

@@ -0,0 +1,6 @@
+contract I {
+  function f() external {}
+}
+contract A is I {}
+contract B is I {}
+contract C is A, B {}

test/libsolidity/syntaxTests/inheritance/override/remove_view.sol

@@ -1,4 +1,5 @@
 contract B { function f() public view {} }
 contract C is B { function f() public {} }
 // ----
+// TypeError: (61-83): Overriding function is missing 'override' specifier.
 // TypeError: (61-83): Overriding function changes state mutability from "view" to "nonpayable".

test/libsolidity/syntaxTests/inheritance/super_on_external.sol

@@ -2,9 +2,9 @@ contract A {
     function f() external pure {}
 }
 contract B is A {
-    function f() public pure {
+    function f() public override pure {
         super.f();
     }
 }
 // ----
-// TypeError: (106-113): Member "f" not found or not visible after argument-dependent lookup in contract super B.
+// TypeError: (115-122): Member "f" not found or not visible after argument-dependent lookup in contract super B.

test/libsolidity/syntaxTests/modifiers/illegal_modifier_override.sol

@@ -1,4 +1,5 @@
 contract A { modifier mod(uint a) { _; } }
 contract B is A { modifier mod(uint8 a) { _; } }
 // ----
+// TypeError: (61-89): Overriding modifier is missing 'override' specifier.
 // TypeError: (61-89): Override changes modifier signature.

test/libsolidity/syntaxTests/modifiers/modifier_overrides_function.sol

@@ -2,4 +2,4 @@ contract A { modifier mod(uint a) { _; } }
 contract B is A { function mod(uint a) public { } }
 // ----
 // DeclarationError: (61-92): Identifier already declared.
-// TypeError: (13-40): Override changes modifier to function.
+// TypeError: (61-92): Override changes modifier to function.

test/libsolidity/syntaxTests/nameAndTypeResolution/030_redeclare_implemented_abstract_function_as_abstract.sol

@@ -1,5 +1,6 @@
 contract base { function foo() public; }
-contract derived is base { function foo() public {} }
+contract derived is base { function foo() public override {} }
 contract wrong is derived { function foo() public; }
 // ----
-// TypeError: (123-145): Redeclaring an already implemented function as abstract
+// TypeError: (132-154): Overriding function is missing 'override' specifier.
+// TypeError: (132-154): Redeclaring an already implemented function as abstract

test/libsolidity/syntaxTests/nameAndTypeResolution/055_inheritance_diamond_basic.sol

@@ -2,6 +2,7 @@ contract root { function rootFunction() public {} }
 contract inter1 is root { function f() public {} }
 contract inter2 is root { function f() public {} }
 contract derived is root, inter2, inter1 {
-    function g() public { f(); rootFunction(); }
+	function g() public { f(); rootFunction(); }
+	function f() override(inter1, inter2) public {}
 }
 // ----

test/libsolidity/syntaxTests/nameAndTypeResolution/059_illegal_override_visibility.sol

@@ -1,4 +1,5 @@
 contract B { function f() internal {} }
 contract C is B { function f() public {} }
 // ----
+// TypeError: (58-80): Overriding function is missing 'override' specifier.
 // TypeError: (58-80): Overriding function visibility differs.

test/libsolidity/syntaxTests/nameAndTypeResolution/060_complex_inheritance.sol

@@ -1,5 +1,5 @@
 contract A { function f() public { uint8 x = C(0).g(); } }
 contract B { function f() public {} function g() public returns (uint8) {} }
-contract C is A, B { }
+contract C is A, B { function f() public override (A, B) { A.f(); } }
 // ----
 // Warning: (35-42): Unused local variable.

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

@@ -3,5 +3,5 @@ contract A {
     function() external { x = 1; }
 }
 contract C is A {
-    function() external { x = 2; }
+    function() override external { x = 2; }
 }

test/libsolidity/syntaxTests/nameAndTypeResolution/149_test_for_bug_override_function_with_bytearray_type.sol

@@ -2,7 +2,7 @@ contract Vehicle {
     function f(bytes calldata) external returns (uint256 r) {r = 1;}
 }
 contract Bike is Vehicle {
-    function f(bytes calldata) external returns (uint256 r) {r = 42;}
+    function f(bytes calldata) override external returns (uint256 r) {r = 42;}
 }
 // ----
 // Warning: (23-87): Function state mutability can be restricted to pure

test/libsolidity/syntaxTests/nameAndTypeResolution/181_override_changes_return_types.sol

@@ -2,7 +2,7 @@ contract base {
     function f(uint a) public returns (uint) { }
 }
 contract test is base {
-    function f(uint a) public returns (uint8) { }
+    function f(uint a) public override returns (uint8) { }
 }
 // ----
-// TypeError: (95-140): Overriding function return types differ.
+// TypeError: (95-149): Overriding function return types differ.

test/libsolidity/syntaxTests/nameAndTypeResolution/182_equal_overload.sol

@@ -4,4 +4,3 @@ contract C {
 }
 // ----
 // DeclarationError: (17-66): Function with same name and arguments defined twice.
-// TypeError: (17-66): Overriding function return types differ.

test/libsolidity/syntaxTests/nameAndTypeResolution/358_illegal_override_payable.sol

@@ -1,4 +1,5 @@
 contract B { function f() payable public {} }
 contract C is B { function f() public {} }
 // ----
+// TypeError: (64-86): Overriding function is missing 'override' specifier.
 // TypeError: (64-86): Overriding function changes state mutability from "payable" to "nonpayable".

test/libsolidity/syntaxTests/nameAndTypeResolution/359_illegal_override_payable_nonpayable.sol

@@ -1,4 +1,5 @@
 contract B { function f() public {} }
 contract C is B { function f() payable public {} }
 // ----
+// TypeError: (56-86): Overriding function is missing 'override' specifier.
 // TypeError: (56-86): Overriding function changes state mutability from "nonpayable" to "payable".

test/libsolidity/syntaxTests/nameAndTypeResolution/423_using_interface.sol

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

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

@@ -5,7 +5,7 @@ interface I {
     function() external;
 }
 contract C is I {
-    function f() public {
+    function f() public override {
     }
 }
 // ----

test/libsolidity/syntaxTests/nameAndTypeResolution/425_interface_implement_public_contract.sol

@@ -2,6 +2,6 @@ interface I {
     function f() external;
 }
 contract C is I {
-    function f() public {
+    function f() public override {
     }
 }

test/libsolidity/syntaxTests/unimplemented_super_function.sol

@@ -2,7 +2,7 @@ contract a {
     function f() public;
 }
 contract b is a {
-    function f() public { super.f(); }
+    function f() public override { super.f(); }
 }
 // ----
-// TypeError: (84-91): Member "f" not found or not visible after argument-dependent lookup in contract super b.
+// TypeError: (93-100): Member "f" not found or not visible after argument-dependent lookup in contract super b.

test/libsolidity/syntaxTests/unimplemented_super_function_derived.sol

@@ -2,11 +2,11 @@ contract a {
     function f() public;
 }
 contract b is a {
-    function f() public { super.f(); }
+    function f() public override { super.f(); }
 }
 contract c is a,b {
     // No error here.
-    function f() public { super.f(); }
+    function f() public override(a, b) { super.f(); }
 }
 // ----
-// TypeError: (84-91): Member "f" not found or not visible after argument-dependent lookup in contract super b.
+// TypeError: (93-100): Member "f" not found or not visible after argument-dependent lookup in contract super b.

test/libsolidity/syntaxTests/viewPureChecker/interface.sol

@@ -2,5 +2,5 @@ interface D {
     function f() view external;
 }
 contract C is D {
-    function f() view external {}
+    function f() override view external {}
 }

test/libsolidity/syntaxTests/viewPureChecker/overriding_fail.sol

@@ -4,13 +4,13 @@ contract D {
     function g() public pure {}
 }
 contract C1 is D {
-    function f() public {}
-    function g() public view {}
+    function f() public override {}
+    function g() public override view {}
 }
 contract C2 is D {
-    function g() public {}
+    function g() public override {}
 }
 // ----
-// TypeError: (118-140): Overriding function changes state mutability from "view" to "nonpayable".
-// TypeError: (145-172): Overriding function changes state mutability from "pure" to "view".
-// TypeError: (198-220): Overriding function changes state mutability from "pure" to "nonpayable".
+// TypeError: (118-149): Overriding function changes state mutability from "view" to "nonpayable".
+// TypeError: (154-190): Overriding function changes state mutability from "pure" to "view".
+// TypeError: (216-247): Overriding function changes state mutability from "pure" to "nonpayable".

test/libsolidity/syntaxTests/viewPureChecker/overriding_no_restrict_warning.sol

@@ -3,5 +3,5 @@ contract D {
     function f() public { x = 2; }
 }
 contract C is D {
-    function f() public {}
+    function f() public override {}
 }