Fix #13286 FN constParameterPointer with decrement (regression) (#6979)

Author: chrchr-github

lib/checkother.cpp

@@ -1688,7 +1688,7 @@ void CheckOther::checkConstPointer()
         else if (Token::simpleMatch(parent, "[") && parent->astOperand1() == tok && tok != nameTok)
             deref = DEREF;
         else if (Token::Match(parent, "%op%") && Token::simpleMatch(parent->astParent(), "."))
-            deref = DEREF;
+            deref = MEMBER;
         else if (Token::simpleMatch(parent, "."))
             deref = MEMBER;
         else if (astIsRangeBasedForDecl(tok))
@@ -1707,12 +1707,12 @@ void CheckOther::checkConstPointer()
                         continue;
                 }
             }
-            if (Token::Match(gparent, "%cop%") && !gparent->isUnaryOp("&") && !gparent->isUnaryOp("*"))
-                continue;
             if (hasIncDecPlus) {
                 parent = gparent;
                 gparent = gparent ? gparent->astParent() : nullptr;
             }
+            if (Token::Match(gparent, "%cop%") && !gparent->isUnaryOp("&") && !gparent->isUnaryOp("*"))
+                continue;
             int argn = -1;
             if (Token::simpleMatch(gparent, "return")) {
                 const Function* function = gparent->scope()->function;
@@ -1744,6 +1744,8 @@ void CheckOther::checkConstPointer()
             int argn = -1;
             if (Token::Match(parent, "%oror%|%comp%|&&|?|!|-|<<"))
                 continue;
+            if (hasIncDecPlus && !parent->astParent())
+                continue;
             if (Token::simpleMatch(parent, "(") && Token::Match(parent->astOperand1(), "if|while"))
                 continue;
             if (Token::simpleMatch(parent, "=") && parent->astOperand1() == tok)

test/testother.cpp

@@ -4313,6 +4313,18 @@ class TestOther : public TestFixture {
               "}\n");
         ASSERT_EQUALS("[test.cpp:1]: (style) Parameter 'b' can be declared as pointer to const\n",
                       errout_str());
+
+        check("struct S { int a; };\n" // #13286
+              "void f(struct S* s) {\n"
+              "    if ((--s)->a >= 0) {}\n"
+              "}\n"
+              "void g(struct S* s) {\n"
+              "    --s;\n"
+              "    if (s->a >= 0) {}\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:2]: (style) Parameter 's' can be declared as pointer to const\n"
+                      "[test.cpp:5]: (style) Parameter 's' can be declared as pointer to const\n",
+                      errout_str());
     }
 
     void constArray() {