[PATCH] D117593: [clang-tidy] Change google-explicit-constructor to ignore conversions and operators marked `explicit(false)`

[Nathan James via Phabricator via cfe-commits]

njames93 created this revision.
njames93 added reviewers: alexfh, aaron.ballman, LegalizeAdulthood.
Herald added subscribers: carlosgalvezp, xazax.hun.
njames93 requested review of this revision.
Herald added a project: clang-tools-extra.
Herald added a subscriber: cfe-commits.

These `explicit(cond)` feature in c++20 can be used to specify if a declaration should be implicit or explicit.
For these cases we shouldn't produce any warning as the developer is already enforcing a specific behaviour.

Fixes https://llvm.org/PR53115.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D117593

Files:
  clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.cpp
  clang-tools-extra/docs/ReleaseNotes.rst
  clang-tools-extra/test/clang-tidy/checkers/google-explicit-constructor-cxx20.cpp


Index: clang-tools-extra/test/clang-tidy/checkers/google-explicit-constructor-cxx20.cpp
===================================================================
--- /dev/null
+++ clang-tools-extra/test/clang-tidy/checkers/google-explicit-constructor-cxx20.cpp
@@ -0,0 +1,17 @@
+// RUN: %check_clang_tidy -std=c++20 %s google-explicit-constructor %t
+
+struct Foo {
+  Foo(int) {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: single-argument constructors must be marked explicit to avoid unintentional implicit conversions
+  // CHECK-FIXES: {{^}}  explicit Foo(int) {}
+  explicit Foo(long) {}
+  explicit(false) Foo(float) {}
+  explicit(true) Foo(double) {}
+
+  operator int() const;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: 'operator int' must be marked explicit to avoid unintentional implicit conversions
+  // CHECK-FIXES: {{^}}  explicit operator int() const;
+  explicit operator long() const;
+  explicit(false) operator float() const;
+  explicit(true) operator double() const;
+};
Index: clang-tools-extra/docs/ReleaseNotes.rst
===================================================================
--- clang-tools-extra/docs/ReleaseNotes.rst
+++ clang-tools-extra/docs/ReleaseNotes.rst
@@ -156,6 +156,10 @@
 - Removed default setting ``cppcoreguidelines-explicit-virtual-functions.IgnoreDestructors = "true"``,
   to match the current state of the C++ Core Guidelines.
 
+- Updated :doc:`google-explicit-constructor
+  <clang-tidy/checks/google-explicit-constructor>` check to ignore constructors
+  or conversion operators where they are marked ``explicit(false)``.
+
 - Updated :doc:`google-readability-casting
   <clang-tidy/checks/google-readability-casting>` to diagnose and fix functional
   casts, to achieve feature parity with the corresponding ``cpplint.py`` check.
Index: clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.cpp
+++ clang-tools-extra/clang-tidy/google/ExplicitConstructorCheck.cpp
@@ -88,6 +88,8 @@
       Result.Nodes.getNodeAs<CXXConversionDecl>("conversion")) {
     if (Conversion->isOutOfLine())
       return;
+    if (Conversion->getExplicitSpecifier().isSpecified())
+      return;
     SourceLocation Loc = Conversion->getLocation();
     // Ignore all macros until we learn to ignore specific ones (e.g. used in
     // gmock to define matchers).
@@ -133,7 +135,7 @@
   }
 
   if (Ctor->isExplicit() || Ctor->isCopyOrMoveConstructor() ||
-      TakesInitializerList)
+      TakesInitializerList || Ctor->getExplicitSpecifier().isSpecified())
     return;
 
   bool SingleArgument =


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