Extract tests.

test/libsolidity/syntaxTests/constructor/overriding_constructor.sol

@@ -0,0 +1,6 @@
+// It is fine to "override" constructor of a base class since it is invisible
+contract A { function A() public { } }
+contract B is A { function A() public pure returns (uint8) {} }
+// ----
+// Warning: (91-114): Defining constructors as functions with the same name as the contract is deprecated. Use "constructor(...) { ... }" instead.
+// Warning: (135-178): This declaration shadows an existing declaration.