Disallow using modifiers not in the current contract or in base contracts.

libsolidity/analysis/TypeChecker.cpp

@@ -630,7 +630,19 @@ void TypeChecker::visitManually(
 	vector<ASTPointer<VariableDeclaration>> emptyParameterList;
 	vector<ASTPointer<VariableDeclaration>> const* parameters = nullptr;
 	if (auto modifierDecl = dynamic_cast<ModifierDefinition const*>(declaration))
+	{
 		parameters = &modifierDecl->parameters();
+		if (auto const* modifierContract = dynamic_cast<ContractDefinition const*>(modifierDecl->scope()))
+			if (m_currentContract)
+			{
+				if (!contains(m_currentContract->annotation().linearizedBaseContracts, modifierContract))
+					m_errorReporter.typeError(
+						9428_error,
+						_modifier.location(),
+						"Can only use modifiers defined in the current contract or in base contracts."
+					);
+			}
+	}
 	else
 		// check parameters for Base constructors
 		for (ContractDefinition const* base: _bases)

test/libsolidity/syntaxTests/modifiers/access_in_library.sol

@@ -0,0 +1,9 @@
+library L {
+    modifier m() { _; }
+}
+contract C {
+    function f() L.m public {
+    }
+}
+// ----
+// TypeError 9428: (68-71): Can only use modifiers defined in the current contract or in base contracts.

test/libsolidity/syntaxTests/modifiers/cross_contract_access.sol

@@ -0,0 +1,9 @@
+contract C {
+    modifier m() { _; }
+}
+contract D {
+    function f() C.m public {
+    }
+}
+// ----
+// TypeError 9428: (69-72): Can only use modifiers defined in the current contract or in base contracts.

test/libsolidity/syntaxTests/modifiers/cross_contract_base.sol

@@ -0,0 +1,8 @@
+contract C {
+    modifier m() { _; }
+}
+contract D is C {
+    function f() C.m public {
+    }
+}
+// ----

test/libsolidity/syntaxTests/modifiers/cross_contract_unrelated.sol

@@ -0,0 +1,11 @@
+contract A {}
+contract C is A {
+    modifier m() { _; }
+}
+contract D is A {
+    function f() C.m public {
+    }
+}
+contract T is D, C {}
+// ----
+// TypeError 9428: (93-96): Can only use modifiers defined in the current contract or in base contracts.

test/libsolidity/syntaxTests/modifiers/library_via_using.sol

@@ -0,0 +1,10 @@
+library L {
+    modifier m() { _; }
+}
+contract C {
+    using L for *;
+    function f() L.m public {
+    }
+}
+// ----
+// TypeError 9428: (87-90): Can only use modifiers defined in the current contract or in base contracts.