[PATCH] D74692: [clang-tidy] Make bugprone-use-after-move ignore std::move for const values

[Zinovy Nis via Phabricator via cfe-commits]

zinovy.nis created this revision.
zinovy.nis added reviewers: mboehme, alexfh.
zinovy.nis added a project: clang-tools-extra.
Herald added subscribers: cfe-commits, mgehre, xazax.hun.
Herald added a project: clang.

std::move for const values is NO-OP, so it has no sense to report it in bugprone-use-after-move

  void simpleConst(const A a) {
    A other_a = std::move(a); // no actual move takes place here,
    a.foo();                  // so this call is safe and must not be reported.
  }

Anyway, redundant std::move for consts can be found with ```performance-move-const-arg``` check.


Repository:
  rCTE Clang Tools Extra

https://reviews.llvm.org/D74692

Files:
  clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp
  clang-tools-extra/test/clang-tidy/checkers/bugprone-use-after-move.cpp


Index: clang-tools-extra/test/clang-tidy/checkers/bugprone-use-after-move.cpp
===================================================================
--- clang-tools-extra/test/clang-tidy/checkers/bugprone-use-after-move.cpp
+++ clang-tools-extra/test/clang-tidy/checkers/bugprone-use-after-move.cpp
@@ -129,6 +129,14 @@
   // CHECK-NOTES: [[@LINE-3]]:15: note: move occurred here
 }
 
+// Simple case for const value.
+void simpleConst(const A a) {
+  A other_a = std::move(a);
+  a.foo();
+  // CHECK-NOTES-NOT: [[@LINE-1]]:3: warning: 'a' used after it was moved
+  // CHECK-NOTES-NOT: [[@LINE-3]]:15: note: move occurred here
+}
+
 // A warning should only be emitted for one use-after-move.
 void onlyFlagOneUseAfterMove() {
   A a;
@@ -314,8 +322,8 @@
     auto lambda = [a] {
       std::move(a);
       a.foo();
-      // CHECK-NOTES: [[@LINE-1]]:7: warning: 'a' used after it was moved
-      // CHECK-NOTES: [[@LINE-3]]:7: note: move occurred here
+      // CHECK-NOTES-NOT: [[@LINE-1]]:7: warning: 'a' used after it was moved
+      // CHECK-NOTES-NOT: [[@LINE-3]]:7: note: move occurred here
     };
   }
   // This is just as true if the variable was declared inside the lambda.
@@ -721,14 +729,14 @@
     const A a;
     std::move(a);
     passByConstPointer(&a);
-    // CHECK-NOTES: [[@LINE-1]]:25: warning: 'a' used after it was moved
-    // CHECK-NOTES: [[@LINE-3]]:5: note: move occurred here
+    // CHECK-NOTES-NOT: [[@LINE-1]]:25: warning: 'a' used after it was moved
+    // CHECK-NOTES-NOT: [[@LINE-3]]:5: note: move occurred here
   }
   const A a;
   std::move(a);
   passByConstReference(a);
-  // CHECK-NOTES: [[@LINE-1]]:24: warning: 'a' used after it was moved
-  // CHECK-NOTES: [[@LINE-3]]:3: note: move occurred here
+  // CHECK-NOTES-NOT: [[@LINE-1]]:24: warning: 'a' used after it was moved
+  // CHECK-NOTES-NOT: [[@LINE-3]]:3: note: move occurred here
 }
 
 // Clearing a standard container using clear() is treated as a
Index: clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp
+++ clang-tools-extra/clang-tidy/bugprone/UseAfterMoveCheck.cpp
@@ -425,13 +425,17 @@
 }
 
 void UseAfterMoveCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *Arg = Result.Nodes.getNodeAs<DeclRefExpr>("arg");
+
+  if (Arg->getType().isConstQualified())
+    return;
+
   const auto *ContainingLambda =
       Result.Nodes.getNodeAs<LambdaExpr>("containing-lambda");
   const auto *ContainingFunc =
       Result.Nodes.getNodeAs<FunctionDecl>("containing-func");
   const auto *CallMove = Result.Nodes.getNodeAs<CallExpr>("call-move");
   const auto *MovingCall = Result.Nodes.getNodeAs<Expr>("moving-call");
-  const auto *Arg = Result.Nodes.getNodeAs<DeclRefExpr>("arg");
 
   if (!MovingCall || !MovingCall->getExprLoc().isValid())
     MovingCall = CallMove;


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