Fixed #10495 (False positive: unreadVariable when assigning to reference returned by method)

Author: danmar

lib/astutils.cpp

@@ -2627,6 +2627,14 @@ bool isNullOperand(const Token *expr)
 
 bool isGlobalData(const Token *expr, bool cpp)
 {
+    // function call that returns reference => assume global data
+    if (expr && expr->str() == "(" && expr->valueType() && expr->valueType()->reference != Reference::None) {
+        if (expr->isBinaryOp())
+            return true;
+        if (expr->astOperand1() && precedes(expr->astOperand1(), expr))
+            return true;
+    }
+
     bool globalData = false;
     bool var = false;
     visitAstNodes(expr,

test/testunusedvar.cpp

@@ -173,6 +173,7 @@ class TestUnusedVar : public TestFixture {
         TEST_CASE(localvarStruct9);
         TEST_CASE(localvarStruct10);
         TEST_CASE(localvarStruct11); // 10095
+        TEST_CASE(localvarStruct12); // #10495
         TEST_CASE(localvarStructArray);
         TEST_CASE(localvarUnion1);
 
@@ -4509,6 +4510,16 @@ class TestUnusedVar : public TestFixture {
         ASSERT_EQUALS("", errout.str());
     }
 
+    void localvarStruct12() { // #10495
+        functionVariableUsage("struct S { bool& Ref(); };\n"
+                              "\n"
+                              "void Set() {\n"
+                              "    S s;\n"
+                              "    s.Ref() = true;\n"
+                              "}");
+        ASSERT_EQUALS("", errout.str());
+    }
+
     void localvarStructArray() {
         // extracttests.start: struct X {int a;};