From 850ad0fed97839ff48a187a30dd1c06b5972d873 Mon Sep 17 00:00:00 2001
From: chrchr-github <78114321+chrchr-github@users.noreply.github.com>
Date: Wed, 9 Mar 2022 18:21:47 +0100
Subject: [PATCH] #8451: Add error message for unused casts, log unhandled
 errors (#3883)

* #8451: Add error message for unused casts, log unhandled errors

* Fix TODO

* Fix TODO
---
 lib/checkother.cpp               | 12 +++++++++---
 test/testincompletestatement.cpp |  5 ++++-
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/lib/checkother.cpp b/lib/checkother.cpp
index a8a2df548..d2a0bbde8 100644
--- a/lib/checkother.cpp
+++ b/lib/checkother.cpp
@@ -1833,7 +1833,7 @@ void CheckOther::checkIncompleteStatement()
 
         const Token *rtok = nextAfterAstRightmostLeaf(tok);
         if (!Token::simpleMatch(tok->astParent(), ";") && !Token::simpleMatch(rtok, ";") &&
-            !Token::Match(tok->previous(), ";|}|{ %any% ;"))
+            !Token::Match(tok->previous(), ";|}|{ %any% ;") && !(mTokenizer->isCPP() && tok->isCast() && !tok->astParent()))
             continue;
         // Skip statement expressions
         if (Token::simpleMatch(rtok, "; } )"))
@@ -1868,8 +1868,14 @@ void CheckOther::constStatementError(const Token *tok, const std::string &type,
         msg = "Redundant code: Found a statement that begins with " + std::string(valueTok->isNumber() ? "numeric" : "string") + " constant.";
     else if (!tok)
         msg = "Redundant code: Found a statement that begins with " + type + " constant.";
-    else
-        return; // Strange!
+    else if (tok->isCast() && tok->tokType() == Token::Type::eExtendedOp) {
+        msg = "Found unused cast ";
+        msg += valueTok ? "of expression '" + valueTok->expressionString() + "'." : "expression.";
+    }
+    else {
+        reportError(tok, Severity::debug, "debug", "constStatementError not handled.");
+        return;
+    }
     reportError(tok, Severity::warning, "constStatement", msg, CWE398, inconclusive ? Certainty::inconclusive : Certainty::normal);
 }
 
diff --git a/test/testincompletestatement.cpp b/test/testincompletestatement.cpp
index f50358888..8a816c891 100644
--- a/test/testincompletestatement.cpp
+++ b/test/testincompletestatement.cpp
@@ -170,7 +170,7 @@ private:
               "    (void)c;\n"
               "  }\n"
               "}");
-        ASSERT_EQUALS("", errout.str());
+        TODO_ASSERT_EQUALS("", "[test.cpp:9]: (debug) constStatementError not handled.\n", errout.str());
     }
 
     void test_numeric() {
@@ -375,6 +375,7 @@ private:
                       "[test.cpp:5]: (warning) Redundant code: Found a statement that begins with numeric constant.\n"
                       "[test.cpp:6]: (warning, inconclusive) Found suspicious operator '!'\n"
                       "[test.cpp:7]: (warning, inconclusive) Found suspicious operator '!'\n"
+                      "[test.cpp:8]: (warning) Found unused cast of expression '!x'.\n"
                       "[test.cpp:9]: (warning, inconclusive) Found suspicious operator '~'\n", errout.str());
 
         check("void f1(int x) { x; }", true);
@@ -383,6 +384,8 @@ private:
         check("void f() { if (Type t; g(t)) {} }"); // #9776
         ASSERT_EQUALS("", errout.str());
 
+        check("void f(int x) { static_cast<unsigned>(x); }");
+        ASSERT_EQUALS("[test.cpp:1]: (warning) Found unused cast of expression 'x'.\n", errout.str());
     }
 
     void vardecl() {