Extra asserts, test renaming, test for super in modifiers

libsolidity/codegen/CompilerContext.cpp

@@ -286,7 +286,11 @@ FunctionDefinition const& CompilerContext::superFunction(FunctionDefinition cons
 	solAssert(m_mostDerivedContract, "No most derived contract set.");
 	ContractDefinition const* super = _base.superContract(mostDerivedContract());
 	solAssert(super, "Super contract not available.");
-	return _function.resolveVirtual(mostDerivedContract(), super);
+
+	FunctionDefinition const& resolvedFunction = _function.resolveVirtual(mostDerivedContract(), super);
+	solAssert(resolvedFunction.isImplemented(), "");
+
+	return resolvedFunction;
 }
 
 ContractDefinition const& CompilerContext::mostDerivedContract() const

libsolidity/codegen/ContractCompiler.cpp

@@ -604,6 +604,8 @@ bool ContractCompiler::visit(VariableDeclaration const& _variableDeclaration)
 
 bool ContractCompiler::visit(FunctionDefinition const& _function)
 {
+	solAssert(_function.isImplemented(), "");
+
 	CompilerContext::LocationSetter locationSetter(m_context, _function);
 
 	m_context.startFunction(_function);

test/libsolidity/syntaxTests/modifiers/cross_contract_super.sol

@@ -0,0 +1,9 @@
+contract C {
+    modifier m() { _; }
+}
+contract D is C {
+    function f() super.m public {
+    }
+}
+// ----
+// DeclarationError 7920: (74-81): Identifier not found or not unique.