Take revert statement into account in control flow graph.

libsolidity/analysis/ControlFlowBuilder.cpp

@@ -236,6 +236,16 @@ bool ControlFlowBuilder::visit(Throw const& _throw)
 	return false;
 }
 
+bool ControlFlowBuilder::visit(RevertStatement const& _revert)
+{
+	solAssert(!!m_currentNode, "");
+	solAssert(!!m_revertNode, "");
+	visitNode(_revert);
+	connect(m_currentNode, m_revertNode);
+	m_currentNode = newLabel();
+	return false;
+}
+
 bool ControlFlowBuilder::visit(PlaceholderStatement const&)
 {
 	solAssert(!!m_currentNode, "");

libsolidity/analysis/ControlFlowBuilder.h

@@ -56,6 +56,7 @@ private:
 	bool visit(Break const&) override;
 	bool visit(Continue const&) override;
 	bool visit(Throw const&) override;
+	bool visit(RevertStatement const&) override;
 	bool visit(PlaceholderStatement const&) override;
 	bool visit(FunctionCall const& _functionCall) override;
 	bool visit(ModifierInvocation const& _modifierInvocation) override;

test/libsolidity/syntaxTests/errors/duplicate.sol

@@ -0,0 +1,21 @@
+==== Source: A ====
+
+error E();
+
+==== Source: B ====
+
+error E();
+
+==== Source: C ====
+
+import "A" as A;
+import "B" as B;
+
+contract Test {
+    function f() public pure {
+        revert A.E();
+    }
+    function g() public pure {
+        revert B.E();
+    }
+}

test/libsolidity/syntaxTests/errors/unreachable.sol

@@ -0,0 +1,10 @@
+contract C {
+    error E();
+    uint x = 2;
+    function f() public {
+        revert E();
+        x = 4;
+    }
+}
+// ----
+// Warning 5740: (98-103): Unreachable code.