ControlFlowAnalyser: Also consider called functions in a flow

test/libsolidity/syntaxTests/multiSource/free_function_control_flow_analysis.sol

@@ -0,0 +1,12 @@
+==== Source: s1.sol ====
+function normal() pure returns (uint) { return 1337; }
+function reverting() pure returns (uint) { revert(); }
+==== Source: s2.sol ====
+import "s1.sol";
+contract C
+{
+	function foo() public pure returns (uint) { normal(); }
+	function bar() public pure returns (uint) { reverting(); }
+}
+// ----
+// Warning 6321: (s2.sol:67-71): Unnamed return variable can remain unassigned. Add an explicit return with value to all non-reverting code paths or name the variable.

test/libsolidity/syntaxTests/multiSource/libraries_control_flow_analysis.sol

@@ -0,0 +1,16 @@
+==== Source: s1.sol ====
+library L
+{
+	function normal() public pure returns (uint) { return 1337; }
+	function reverting() public pure returns (uint) { revert(); }
+}
+==== Source: s2.sol ====
+import "s1.sol";
+contract C
+{
+	function foo() public pure returns (uint) { L.normal(); }
+	function bar() public pure returns (uint) { L.reverting(); }
+}
+// ----
+// Warning 6321: (s2.sol:67-71): Unnamed return variable can remain unassigned. Add an explicit return with value to all non-reverting code paths or name the variable.
+// Warning 6321: (s2.sol:126-130): Unnamed return variable can remain unassigned. Add an explicit return with value to all non-reverting code paths or name the variable.

test/libsolidity/syntaxTests/multiSource/split_contract_hierarchy_control_flow_analysis.sol

@@ -0,0 +1,15 @@
+==== Source: s1.sol ====
+contract C
+{
+	function normal() public pure returns (uint) { return 1337; }
+	function reverting() public pure returns (uint) { revert(); }
+}
+==== Source: s2.sol ====
+import "s1.sol";
+contract D is C
+{
+	function foo() public pure returns (uint) { normal(); }
+	function bar() public pure returns (uint) { reverting(); }
+}
+// ----
+// Warning 6321: (s2.sol:72-76): Unnamed return variable can remain unassigned. Add an explicit return with value to all non-reverting code paths or name the variable.

test/libsolidity/syntaxTests/multiSource/split_contract_hierarchy_control_flow_analysis_complex.sol

@@ -0,0 +1,24 @@
+==== Source: s1.sol ====
+contract C
+{
+	function normal(bool x) public pure returns (uint)
+	{
+		if (x)
+			return xxx();
+		else
+			return yyy();
+	}
+	function yyy() public pure returns (uint) { revert(); }
+	function bar() public pure returns (uint) { normal(true); }
+
+	function xxx() public virtual pure returns (uint) { return 1; }
+}
+==== Source: s2.sol ====
+import "s1.sol";
+contract D is C
+{
+	function foo() public pure returns (uint) { normal(false); }
+	function xxx() public override pure returns(uint) { revert(); }
+}
+// ----
+// Warning 6321: (s1.sol:215-219): Unnamed return variable can remain unassigned. Add an explicit return with value to all non-reverting code paths or name the variable.