jvikstrom updated this revision to Diff 204244.
jvikstrom marked an inline comment as done.
jvikstrom added a comment.

- Updated example and fixed edge case in ignoringElidableConstructorCall


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D63149/new/

https://reviews.llvm.org/D63149

Files:
  clang/docs/LibASTMatchersReference.html
  clang/include/clang/ASTMatchers/ASTMatchers.h
  clang/lib/ASTMatchers/Dynamic/Registry.cpp
  clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp

Index: clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
===================================================================
--- clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
+++ clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
@@ -566,6 +566,81 @@
                                        llvm::make_unique<VerifyIdIsBoundTo<CXXMemberCallExpr>>("x")));
 }
 
+TEST(Matcher, IgnoresElidableConstructors) {
+  auto matcher1 = cxxOperatorCallExpr(hasArgument(
+      1, callExpr(hasArgument(
+             0, ignoringElidableMoveConstructorCall(callExpr().bind("c"))))));
+  auto matcher2 = cxxOperatorCallExpr(hasArgument(
+      1, callExpr(hasArgument(0, ignoringElidableMoveConstructorCall(
+                                     integerLiteral().bind("c"))))));
+  auto matcher3 =
+      varDecl(hasInitializer(ignoringElidableMoveConstructorCall(callExpr())));
+
+  auto code1 = "struct H {};"
+               "template<typename T> H B(T A);"
+               "void f(){"
+               "H D1;"
+               "D1=B(B(1));"
+               "}";
+  auto code2 = "struct H {};"
+               "template<typename T> H B(T A);"
+               "void f(){"
+               "H D1;"
+               "D1=B(1);"
+               "}";
+  auto code3 = "struct H {};"
+               "H G();"
+               "void f(){"
+               "H D = G();"
+               "}";
+
+  EXPECT_TRUE(matchesConditionally(code1, matcher1, true, "-std=c++14"));
+  EXPECT_TRUE(matchesConditionally(code1, matcher1, true, "-std=c++17"));
+
+  EXPECT_TRUE(matchesConditionally(code2, matcher2, true, "-std=c++14"));
+  EXPECT_TRUE(matchesConditionally(code2, matcher2, true, "-std=c++17"));
+
+  EXPECT_TRUE(matchesConditionally(code3, matcher3, true, "-std=c++14"));
+  EXPECT_TRUE(matchesConditionally(code3, matcher3, true, "-std=c++17"));
+}
+
+TEST(Matcher, IgnoresElidableInReturn) {
+  auto matcher = expr(ignoringElidableMoveConstructorCall(declRefExpr()));
+  auto code1 = "struct H{};"
+               "H f(){"
+               "H g;"
+               "return g;"
+               "}";
+  auto code2 = "struct H{};"
+               "H f(){"
+               "return H();"
+               "}";
+  EXPECT_TRUE(matchesConditionally(code1, matcher, true, "-std=c++14"));
+  EXPECT_TRUE(matchesConditionally(code1, matcher, true, "-std=c++17"));
+  EXPECT_TRUE(matchesConditionally(code2, matcher, false, "-std=c++14"));
+  EXPECT_TRUE(matchesConditionally(code2, matcher, false, "-std=c++17"));
+}
+
+TEST(Matcher, IgnoreElidableConstructorDoesNotMatchConstructors) {
+  auto matcher = varDecl(
+      hasInitializer(ignoringElidableMoveConstructorCall(cxxConstructExpr())));
+  auto code = "struct H {};"
+              "void f(){"
+              "H D;"
+              "}";
+  EXPECT_TRUE(matchesConditionally(code, matcher, true, "-std=c++14"));
+  EXPECT_TRUE(matchesConditionally(code, matcher, true, "-std=c++17"));
+};
+
+TEST(Matcher, IgnoresElidableDoesNotPreventMatches) {
+  auto matcher = expr(ignoringElidableMoveConstructorCall(integerLiteral()));
+  auto code = "void f(){"
+              "int D = 10;"
+              "}";
+  EXPECT_TRUE(matchesConditionally(code, matcher, true, "-std=c++14"));
+  EXPECT_TRUE(matchesConditionally(code, matcher, true, "-std=c++17"));
+}
+
 TEST(Matcher, BindTheSameNameInAlternatives) {
   StatementMatcher matcher = anyOf(
     binaryOperator(hasOperatorName("+"),
Index: clang/lib/ASTMatchers/Dynamic/Registry.cpp
===================================================================
--- clang/lib/ASTMatchers/Dynamic/Registry.cpp
+++ clang/lib/ASTMatchers/Dynamic/Registry.cpp
@@ -320,6 +320,7 @@
   REGISTER_MATCHER(hasUnqualifiedDesugaredType);
   REGISTER_MATCHER(hasValueType);
   REGISTER_MATCHER(ifStmt);
+  REGISTER_MATCHER(ignoringElidableMoveConstructorCall);
   REGISTER_MATCHER(ignoringImpCasts);
   REGISTER_MATCHER(ignoringImplicit);
   REGISTER_MATCHER(ignoringParenCasts);
Index: clang/include/clang/ASTMatchers/ASTMatchers.h
===================================================================
--- clang/include/clang/ASTMatchers/ASTMatchers.h
+++ clang/include/clang/ASTMatchers/ASTMatchers.h
@@ -6452,6 +6452,56 @@
   return false;
 }
 
+/// Matches expressions that match InnerMatcher that are possibly wrapped in an
+/// elidable constructor.
+///
+/// In C++17 copy elidable constructors are no longer being
+/// generated in the AST as it is not permitted by the standard. They are
+/// however part of the AST in C++14 and earlier. Therefore, to write a matcher
+/// that works in all language modes, the matcher has to skip elidable
+/// constructor AST nodes if they appear in the AST. This matcher can be used to
+/// skip those elidable constructors.
+///
+/// Given
+///
+/// \code
+/// struct H {};
+/// H G();
+/// void f(){
+/// H D = G();
+/// }
+/// \endcode
+///
+/// ``varDecl(hasInitializer(ignoringElidableMoveConstructorCall(callExpr())))``
+/// matches ``H D = G()``
+AST_MATCHER_P(Expr, ignoringElidableMoveConstructorCall,
+              ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
+
+  if (const auto *expr_cleanups = dyn_cast<ExprWithCleanups>(&Node)) {
+    bool matches = false;
+    for (const auto *obj : expr_cleanups->children()) {
+      if (const auto *cxx_construct_expr = dyn_cast<CXXConstructExpr>(obj)) {
+        matches = matches | ignoringElidableMoveConstructorCall(InnerMatcher)
+                                .matches(*cxx_construct_expr, Finder, Builder);
+      }
+    }
+    return matches;
+  }
+
+  if (const auto *cxx_construct_expr = dyn_cast<CXXConstructExpr>(&Node)) {
+    if (cxx_construct_expr->isElidable()) {
+      if (const auto *materialize_temp = dyn_cast<MaterializeTemporaryExpr>(
+              cxx_construct_expr->getArg(0))) {
+        const auto *first_child =
+            dyn_cast<Expr>(*materialize_temp->children().begin());
+        return InnerMatcher.matches(*first_child, Finder, Builder);
+      }
+      return InnerMatcher.matches(*cxx_construct_expr, Finder, Builder);
+    }
+  }
+  return InnerMatcher.matches(Node, Finder, Builder);
+}
+
 //----------------------------------------------------------------------------//
 // OpenMP handling.
 //----------------------------------------------------------------------------//
Index: clang/docs/LibASTMatchersReference.html
===================================================================
--- clang/docs/LibASTMatchersReference.html
+++ clang/docs/LibASTMatchersReference.html
@@ -5728,6 +5728,30 @@
 </pre></td></tr>
 
 
+<tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1Expr.html";>Expr</a>&gt;</td><td class="name" onclick="toggle('ignoringElidableMoveConstructorCall0')"><a name="ignoringElidableMoveConstructorCall0Anchor">ignoringElidableMoveConstructorCall</a></td><td>ast_matchers::Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1Expr.html";>Expr</a>&gt; InnerMatcher</td></tr>
+<tr><td colspan="4" class="doc" id="ignoringElidableMoveConstructorCall0"><pre>Matches expressions that match InnerMatcher that are possibly wrapped in an
+elidable constructor.
+
+In C++17 copy elidable constructors are no longer being
+generated in the AST as it is not permitted by the standard. They are
+however part of the AST in C++14 and earlier. Therefore, to write a matcher
+that works in all language modes, the matcher has to skip elidable
+constructor AST nodes if they appear in the AST. This matcher can be used to
+skip those elidable constructors.
+
+Given
+
+struct H {};
+H G();
+void f(){
+H D = G();
+}
+
+``varDecl(hasInitializer(ignoringElidableMoveConstructorCall(callExpr())))``
+matches ``H D = G()``
+</pre></td></tr>
+
+
 <tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1Expr.html";>Expr</a>&gt;</td><td class="name" onclick="toggle('ignoringImpCasts0')"><a name="ignoringImpCasts0Anchor">ignoringImpCasts</a></td><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1Expr.html";>Expr</a>&gt; InnerMatcher</td></tr>
 <tr><td colspan="4" class="doc" id="ignoringImpCasts0"><pre>Matches expressions that match InnerMatcher after any implicit casts
 are stripped off.
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