[clang-tidy] Support functional cast in bugprone-dangling-handle (#69067)

Add support for constructor conversion based functional
cast. Allows to detect issues like:
const std::string_view test1 = std::string(a);

Author: PiotrZSL

clang-tools-extra/clang-tidy/bugprone/DanglingHandleCheck.cpp

@@ -33,14 +33,20 @@ handleFrom(const ast_matchers::internal::Matcher<RecordDecl> &IsAHandle,
 
 ast_matchers::internal::Matcher<Stmt> handleFromTemporaryValue(
     const ast_matchers::internal::Matcher<RecordDecl> &IsAHandle) {
+
+  const auto TemporaryExpr = anyOf(
+      cxxBindTemporaryExpr(),
+      cxxFunctionalCastExpr(
+          hasCastKind(CK_ConstructorConversion),
+          hasSourceExpression(ignoringParenImpCasts(cxxBindTemporaryExpr()))));
   // If a ternary operator returns a temporary value, then both branches hold a
   // temporary value. If one of them is not a temporary then it must be copied
   // into one to satisfy the type of the operator.
   const auto TemporaryTernary = conditionalOperator(
-      hasTrueExpression(ignoringParenImpCasts(cxxBindTemporaryExpr())),
-      hasFalseExpression(ignoringParenImpCasts(cxxBindTemporaryExpr())));
+      hasTrueExpression(ignoringParenImpCasts(TemporaryExpr)),
+      hasFalseExpression(ignoringParenImpCasts(TemporaryExpr)));
 
-  return handleFrom(IsAHandle, anyOf(cxxBindTemporaryExpr(), TemporaryTernary));
+  return handleFrom(IsAHandle, anyOf(TemporaryExpr, TemporaryTernary));
 }
 
 ast_matchers::internal::Matcher<RecordDecl> isASequence() {

clang-tools-extra/docs/ReleaseNotes.rst

@@ -207,6 +207,11 @@ New check aliases
 Changes in existing checks
 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+- Improved :doc:`bugprone-dangling-handle
+  <clang-tidy/checks/bugprone/dangling-handle>` check to support functional
+  casting during type conversions at variable initialization, now with improved
+  compatibility for C++17 and later versions.
+
 - Improved :doc:`bugprone-lambda-function-name
   <clang-tidy/checks/bugprone/lambda-function-name>` check by adding option
   `IgnoreMacros` to ignore warnings in macros.

clang-tools-extra/test/clang-tidy/checkers/bugprone/dangling-handle.cpp

@@ -108,6 +108,14 @@ void Positives() {
   std::string_view view4(ReturnsAString());
   // CHECK-MESSAGES-CXX14: [[@LINE-1]]:20: warning: std::basic_string_view outlives
   // CHECK-MESSAGES-CXX17: [[@LINE-2]]:26: warning: std::basic_string_view outlives
+
+  std::string_view view5 = std::string("test");
+  // CHECK-MESSAGES-CXX14: [[@LINE-1]]:20: warning: std::basic_string_view outlives its value [bugprone-dangling-handle]
+  // CHECK-MESSAGES-CXX17: [[@LINE-2]]:28: warning: std::basic_string_view outlives its value [bugprone-dangling-handle]
+
+  std::string_view view6 = std::string{"test"};
+  // CHECK-MESSAGES-CXX14: [[@LINE-1]]:20: warning: std::basic_string_view outlives its value [bugprone-dangling-handle]
+  // CHECK-MESSAGES-CXX17: [[@LINE-2]]:28: warning: std::basic_string_view outlives its value [bugprone-dangling-handle]
 }
 
 void OtherTypes() {