FunctionDefinition.resolveVirtual(): Skip unimplemented functions when lookup happens via super

test/libsolidity/semanticTests/functionCall/inheritance/call_unimplemented_base.sol

@@ -2,13 +2,17 @@ abstract contract I
 {
     function a() internal view virtual returns(uint256);
 }
-abstract contract V is I
+abstract contract J is I
+{
+    function a() internal view virtual override returns(uint256);
+}
+abstract contract V is J
 {
     function b() public view returns(uint256) { return a(); }
 }
 contract C is V
 {
-    function a() internal view override returns (uint256) { return 42;}
+    function a() internal view override returns (uint256) { return 42; }
 }
 // ====
 // compileToEwasm: also

test/libsolidity/semanticTests/functionCall/inheritance/super_skip_unimplemented_in_abstract_contract.sol

@@ -0,0 +1,22 @@
+contract A {
+    function f() public virtual returns (uint) {
+        return 42;
+    }
+}
+
+abstract contract I {
+    function f() external virtual returns (uint);
+}
+
+contract B is A, I {
+    function f() override(A, I) public returns (uint) {
+        // I.f() is before A.f() in the C3 linearized order
+        // but it has no implementation.
+        return super.f();
+    }
+}
+// ====
+// compileToEwasm: also
+// compileViaYul: also
+// ----
+// f() -> 42

test/libsolidity/semanticTests/functionCall/inheritance/super_skip_unimplemented_in_interface.sol

@@ -0,0 +1,22 @@
+contract A {
+    function f() public virtual returns (uint) {
+        return 42;
+    }
+}
+
+interface I {
+    function f() external returns (uint);
+}
+
+contract B is A, I {
+    function f() override(A, I) public returns (uint) {
+        // I.f() is before A.f() in the C3 linearized order
+        // but it has no implementation.
+        return super.f();
+    }
+}
+// ====
+// compileToEwasm: also
+// compileViaYul: also
+// ----
+// f() -> 42