Fix #13888 FP shadowVariable in friend function (#7552)

Co-authored-by: chrchr-github <noreply@github.com>

Author: chrchr-github

lib/checkother.cpp

@@ -4053,7 +4053,8 @@ void CheckOther::checkShadowVariables()
                 continue;
             if (scope.type == ScopeType::eFunction && scope.className == var.name())
                 continue;
-            if (functionScope->functionOf && functionScope->functionOf->isClassOrStructOrUnion() && functionScope->function && functionScope->function->isStatic() &&
+            if (functionScope->functionOf && functionScope->functionOf->isClassOrStructOrUnion() && functionScope->function &&
+                (functionScope->function->isStatic() || functionScope->function->isFriend()) &&
                 shadowed->variable() && !shadowed->variable()->isLocal())
                 continue;
             shadowError(var.nameToken(), shadowed, (shadowed->varId() != 0) ? "variable" : "function");

test/testother.cpp

@@ -12390,6 +12390,12 @@ class TestOther : public TestFixture {
               "}\n"
               "int g() { return 1; }\n");
         ASSERT_EQUALS("", errout_str());
+
+        check("struct S {\n" // #13888
+              "    int i;\n"
+              "    friend int f() { int i = 5; return i; }\n"
+              "};\n");
+        ASSERT_EQUALS("", errout_str());
     }
 
     void knownArgument() {