[clang-tidy] Sequence init statements, declarations, and conditions correctly in if, switch, and while

Summary: Fixes https://bugs.llvm.org/show_bug.cgi?id=36516.

Reviewers: ilya-biryukov, alexfh, aaron.ballman, hokein

Reviewed By: alexfh

Subscribers: xazax.hun, cfe-commits

Tags: #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D49918

llvm-svn: 338932

clang-tools-extra/clang-tidy/utils/ExprSequence.cpp

@@ -139,11 +139,26 @@ const Stmt *ExprSequence::getSequenceSuccessor(const Stmt *S) const {
       if (S == ForRange->getLoopVarStmt())
         return ForRange->getBody();
     } else if (const auto *TheIfStmt = dyn_cast<IfStmt>(Parent)) {
-      // If statement: If a variable is declared inside the condition, the
-      // expression used to initialize the variable is sequenced before the
-      // evaluation of the condition.
+      // If statement:
+      // - Sequence init statement before variable declaration.
+      // - Sequence variable declaration (along with the expression used to
+      //   initialize it) before the evaluation of the condition.
+      if (S == TheIfStmt->getInit())
+        return TheIfStmt->getConditionVariableDeclStmt();
       if (S == TheIfStmt->getConditionVariableDeclStmt())
         return TheIfStmt->getCond();
+    } else if (const auto *TheSwitchStmt = dyn_cast<SwitchStmt>(Parent)) {
+      // Ditto for switch statements.
+      if (S == TheSwitchStmt->getInit())
+        return TheSwitchStmt->getConditionVariableDeclStmt();
+      if (S == TheSwitchStmt->getConditionVariableDeclStmt())
+        return TheSwitchStmt->getCond();
+    } else if (const auto *TheWhileStmt = dyn_cast<WhileStmt>(Parent)) {
+      // While statement: Sequence variable declaration (along with the
+      // expression used to initialize it) before the evaluation of the
+      // condition.
+      if (S == TheWhileStmt->getConditionVariableDeclStmt())
+        return TheWhileStmt->getCond();
     }
   }
 

clang-tools-extra/test/clang-tidy/bugprone-use-after-move.cpp

@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy %s bugprone-use-after-move %t -- -- -std=c++11 -fno-delayed-template-parsing
+// RUN: %check_clang_tidy %s bugprone-use-after-move %t -- -- -std=c++17 -fno-delayed-template-parsing
 
 typedef decltype(nullptr) nullptr_t;
 
@@ -1132,13 +1132,30 @@ void forRangeSequences() {
   }
 }
 
-// If a variable is declared in an if statement, the declaration of the variable
-// (which is treated like a reinitialization by the check) is sequenced before
-// the evaluation of the condition (which constitutes a use).
-void ifStmtSequencesDeclAndCondition() {
+// If a variable is declared in an if, while or switch statement, the init
+// statement (for if and switch) is sequenced before the variable declaration,
+// which in turn is sequenced before the evaluation of the condition.
+void ifWhileAndSwitchSequenceInitDeclAndCondition() {
   for (int i = 0; i < 10; ++i) {
-    if (A a = A()) {
-      std::move(a);
+    A a1;
+    if (A a2 = std::move(a1)) {
+      std::move(a2);
+    }
+  }
+  for (int i = 0; i < 10; ++i) {
+    A a1;
+    if (A a2 = std::move(a1); A a3 = std::move(a2)) {
+      std::move(a3);
+    }
+  }
+  while (A a = A()) {
+    std::move(a);
+  }
+  for (int i = 0; i < 10; ++i) {
+    A a1;
+    switch (A a2 = a1; A a3 = std::move(a2)) {
+      case true:
+        std::move(a3);
     }
   }
 }