Merge pull request #3875 from ethereum/constructorSelfRef

Stricter check for "this" in constructor.

test/libsolidity/syntaxTests/constructor_this.sol

@@ -0,0 +1,12 @@
+contract C {
+    function f() public pure {}
+    constructor() public {
+        C c = this;
+        c.f(); // this does not warn now, but should warn in the future
+        this.f();
+        (this).f();
+    }
+}
+// ----
+// Warning: (172-176): "this" used in constructor. Note that external functions of a contract cannot be called while it is being constructed.
+// Warning: (191-195): "this" used in constructor. Note that external functions of a contract cannot be called while it is being constructed.

test/libsolidity/syntaxTests/parsing/constructor_allowed_this.sol

@@ -0,0 +1,28 @@
+contract A {
+    function a() public pure {
+    }
+}
+contract B {
+    constructor(address) public {
+    }
+    function b(address) public returns (A) {
+        return new A();
+    }
+}
+contract C {
+    B m_b;
+    C m_c;
+    constructor(C other_c) public {
+        m_c = other_c;
+        m_b = new B(this);
+        m_b.b(this).a();
+        g(this).f();
+        other_c.f();
+        m_c.f();
+    }
+    function f() public pure {
+    }
+    function g(C) public view returns (C) {
+        return m_c;
+    }
+}

test/libsolidity/syntaxTests/parsing/constructor_super.sol

@@ -0,0 +1,10 @@
+contract A {
+  function x() pure internal {}
+}
+
+contract B is A {
+  constructor() public {
+    // used to trigger warning about using ``this`` in constructor
+    super.x();
+  }
+}