[clang-tidy] performance-unnecessary-copy-initialization: Consider static functions

Static member functions can be considered the same way
as free functions are, so do that.

Author: pobrn

clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.cpp

@@ -104,14 +104,18 @@ AST_MATCHER_FUNCTION_P(StatementMatcher,
                                 hasArgument(0, hasType(ReceiverType)))));
 }
 
+namespace {
+AST_MATCHER(CXXMethodDecl, isStatic) { return Node.isStatic(); }
+} // namespace
+
 AST_MATCHER_FUNCTION(StatementMatcher, isConstRefReturningFunctionCall) {
   // Only allow initialization of a const reference from a free function if it
   // has no arguments. Otherwise it could return an alias to one of its
   // arguments and the arguments need to be checked for const use as well.
   return callExpr(callee(functionDecl(returns(hasCanonicalType(
                                           matchers::isReferenceToConst())))
                              .bind(FunctionDeclId)),
-                  argumentCountIs(0), unless(callee(cxxMethodDecl())))
+                  argumentCountIs(0), unless(callee(cxxMethodDecl(unless(isStatic())))))
       .bind(InitFunctionCallId);
 }
 

clang-tools-extra/test/clang-tidy/checkers/performance/unnecessary-copy-initialization.cpp

@@ -28,6 +28,8 @@ struct ExpensiveToCopyType {
   template <typename A>
   const A &templatedAccessor() const;
   operator int() const; // Implicit conversion to int.
+
+  static const ExpensiveToCopyType &instance();
 };
 
 template <typename T>
@@ -100,6 +102,28 @@ void PositiveFunctionCall() {
   VarCopyConstructed.constMethod();
 }
 
+void PositiveStaticMethodCall() {
+  const auto AutoAssigned = ExpensiveToCopyType::instance();
+  // CHECK-MESSAGES: [[@LINE-1]]:14: warning: the const qualified variable 'AutoAssigned' is copy-constructed from a const reference; consider making it a const reference [performance-unnecessary-copy-initialization]
+  // CHECK-FIXES: const auto& AutoAssigned = ExpensiveToCopyType::instance();
+  AutoAssigned.constMethod();
+
+  const auto AutoCopyConstructed(ExpensiveToCopyType::instance());
+  // CHECK-MESSAGES: [[@LINE-1]]:14: warning: the const qualified variable 'AutoCopyConstructed'
+  // CHECK-FIXES: const auto& AutoCopyConstructed(ExpensiveToCopyType::instance());
+  AutoCopyConstructed.constMethod();
+
+  const ExpensiveToCopyType VarAssigned = ExpensiveToCopyType::instance();
+  // CHECK-MESSAGES: [[@LINE-1]]:29: warning: the const qualified variable 'VarAssigned'
+  // CHECK-FIXES:   const ExpensiveToCopyType& VarAssigned = ExpensiveToCopyType::instance();
+  VarAssigned.constMethod();
+
+  const ExpensiveToCopyType VarCopyConstructed(ExpensiveToCopyType::instance());
+  // CHECK-MESSAGES: [[@LINE-1]]:29: warning: the const qualified variable 'VarCopyConstructed'
+  // CHECK-FIXES: const ExpensiveToCopyType& VarCopyConstructed(ExpensiveToCopyType::instance());
+  VarCopyConstructed.constMethod();
+}
+
 void PositiveMethodCallConstReferenceParam(const ExpensiveToCopyType &Obj) {
   const auto AutoAssigned = Obj.reference();
   // CHECK-MESSAGES: [[@LINE-1]]:14: warning: the const qualified variable 'AutoAssigned'