[clang-tools-extra] 8b326d5 - [clang-tidy] fix false negative in cppcoreguidelines-missing-std-forward (#83987)

[via cfe-commits]

Author: Qizhi Hu
Date: 2024-03-06T09:27:32+08:00
New Revision: 8b326d59467b941831942c651c585055b3d512e4

URL: https://github.com/llvm/llvm-project/commit/8b326d59467b941831942c651c585055b3d512e4
DIFF: https://github.com/llvm/llvm-project/commit/8b326d59467b941831942c651c585055b3d512e4.diff

LOG: [clang-tidy] fix false negative in cppcoreguidelines-missing-std-forward (#83987)

Try to fix https://github.com/llvm/llvm-project/issues/83845
When `std::forward` is invoked in a function, make sure it uses correct
parameter by checking if the bounded `var` equals the parameter.

Co-authored-by: huqizhi <836744285 at qq.com>

Added: 
    

Modified: 
    clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp
    clang-tools-extra/docs/ReleaseNotes.rst
    clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp

Removed: 
    


################################################################################
diff  --git a/clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp b/clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp
index c633683570f748..87fd8adf997082 100644
--- a/clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp
+++ b/clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp
@@ -112,10 +112,12 @@ void MissingStdForwardCheck::registerMatchers(MatchFinder *Finder) {
 
   auto ForwardCallMatcher = callExpr(
       callExpr().bind("call"), argumentCountIs(1),
-      hasArgument(
-          0, declRefExpr(to(
-                 varDecl(optionally(equalsBoundNode("param"))).bind("var")))),
-      forCallable(anyOf(equalsBoundNode("func"), CapturedInLambda)),
+      hasArgument(0, declRefExpr(to(varDecl().bind("var")))),
+      forCallable(
+          anyOf(allOf(equalsBoundNode("func"),
+                      functionDecl(hasAnyParameter(parmVarDecl(allOf(
+                          equalsBoundNode("param"), equalsBoundNode("var")))))),
+                CapturedInLambda)),
       callee(unresolvedLookupExpr(hasAnyDeclaration(
           namedDecl(hasUnderlyingDecl(hasName("::std::forward")))))),
 

diff  --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 143ae230fc443c..1b839a35c3ed65 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -156,7 +156,8 @@ Changes in existing checks
 
 - Improved :doc:`cppcoreguidelines-missing-std-forward
   <clang-tidy/checks/cppcoreguidelines/missing-std-forward>` check by no longer
-  giving false positives for deleted functions.
+  giving false positives for deleted functions and fix false negative when some
+  parameters are forwarded, but other aren't.
 
 - Cleaned up :doc:`cppcoreguidelines-prefer-member-initializer
   <clang-tidy/checks/cppcoreguidelines/prefer-member-initializer>`

diff  --git a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp
index 20e43f04180ff3..9a50eabf619bd5 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp
@@ -95,6 +95,16 @@ void lambda_value_capture_copy(T&& t) {
   [&,t]() { T other = std::forward<T>(t); };
 }
 
+template <typename X>
+void use(const X &x) {}
+
+template <typename X, typename Y>
+void foo(X &&x, Y &&y) {
+  // CHECK-MESSAGES: :[[@LINE-1]]:21: warning: forwarding reference parameter 'y' is never forwarded inside the function body [cppcoreguidelines-missing-std-forward]
+    use(std::forward<X>(x));
+    use(y);
+}
+
 } // namespace positive_cases
 
 namespace negative_cases {