Added AST matcher for ignoring elidable constructors

Summary: Added AST matcher for ignoring elidable move constructors

Reviewers: hokein, gribozavr

Reviewed By: hokein, gribozavr

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D63149

Patch by Johan Vikström.

llvm-svn: 363262

5 files changed, 210 insertions, 9 deletions

diff --git a/clang/docs/LibASTMatchersReference.html b/clang/docs/LibASTMatchersReference.html
index 255ec4271e3..47f2c8a489e 100644
--- a/clang/docs/LibASTMatchersReference.html
+++ b/clang/docs/LibASTMatchersReference.html
@@ -5728,6 +5728,32 @@ Example matches x (matcher = expr(hasType(cxxRecordDecl(hasName("X")))))
 </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('ignoringElidableConstructorCall0')"><a name="ignoringElidableConstructorCall0Anchor">ignoringElidableConstructorCall</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="ignoringElidableConstructorCall0"><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(any(
+      ignoringElidableConstructorCall(callExpr()),
+      exprWithCleanups(ignoringElidableConstructorCall(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.
diff --git a/clang/include/clang/ASTMatchers/ASTMatchers.h b/clang/include/clang/ASTMatchers/ASTMatchers.h
index d973b48a176..d3ebbff42e7 100644
--- a/clang/include/clang/ASTMatchers/ASTMatchers.h
+++ b/clang/include/clang/ASTMatchers/ASTMatchers.h
@@ -6452,6 +6452,44 @@ AST_MATCHER(FunctionDecl, hasTrailingReturn) {
   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(any(
+///       ignoringElidableConstructorCall(callExpr()),
+///       exprWithCleanups(ignoringElidableConstructorCall(callExpr()))))``
+/// matches ``H D = G()``
+AST_MATCHER_P(Expr, ignoringElidableConstructorCall,
+              ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
+  if (const auto *CtorExpr = dyn_cast<CXXConstructExpr>(&Node)) {
+    if (CtorExpr->isElidable()) {
+      if (const auto *MaterializeTemp =
+              dyn_cast<MaterializeTemporaryExpr>(CtorExpr->getArg(0))) {
+        return InnerMatcher.matches(*MaterializeTemp->GetTemporaryExpr(),
+                                    Finder, Builder);
+      }
+    }
+  }
+  return InnerMatcher.matches(Node, Finder, Builder);
+}
+
 //----------------------------------------------------------------------------//
 // OpenMP handling.
 //----------------------------------------------------------------------------//
diff --git a/clang/lib/ASTMatchers/Dynamic/Registry.cpp b/clang/lib/ASTMatchers/Dynamic/Registry.cpp
index fedb9dd2abe..8c37689a4c8 100644
--- a/clang/lib/ASTMatchers/Dynamic/Registry.cpp
+++ b/clang/lib/ASTMatchers/Dynamic/Registry.cpp
@@ -320,6 +320,7 @@ RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER(hasUnqualifiedDesugaredType);
   REGISTER_MATCHER(hasValueType);
   REGISTER_MATCHER(ifStmt);
+  REGISTER_MATCHER(ignoringElidableConstructorCall);
   REGISTER_MATCHER(ignoringImpCasts);
   REGISTER_MATCHER(ignoringImplicit);
   REGISTER_MATCHER(ignoringParenCasts);
diff --git a/clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp b/clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
index 01b168da2b7..5515680da6e 100644
--- a/clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
+++ b/clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
@@ -566,6 +566,74 @@ TEST(Matcher, BindMatchedNodes) {
                                        llvm::make_unique<VerifyIdIsBoundTo<CXXMemberCallExpr>>("x")));
 }
 
+TEST(Matcher, IgnoresElidableConstructors) {
+  EXPECT_TRUE(
+      matches("struct H {};"
+              "template<typename T> H B(T A);"
+              "void f() {"
+              "  H D1;"
+              "  D1 = B(B(1));"
+              "}",
+              cxxOperatorCallExpr(hasArgument(
+                  1, callExpr(hasArgument(
+                         0, ignoringElidableConstructorCall(callExpr()))))),
+              LanguageMode::Cxx11OrLater));
+  EXPECT_TRUE(
+      matches("struct H {};"
+              "template<typename T> H B(T A);"
+              "void f() {"
+              "  H D1;"
+              "  D1 = B(1);"
+              "}",
+              cxxOperatorCallExpr(hasArgument(
+                  1, callExpr(hasArgument(0, ignoringElidableConstructorCall(
+                                                 integerLiteral()))))),
+              LanguageMode::Cxx11OrLater));
+  EXPECT_TRUE(matches(
+      "struct H {};"
+      "H G();"
+      "void f() {"
+      "  H D = G();"
+      "}",
+      varDecl(hasInitializer(anyOf(
+          ignoringElidableConstructorCall(callExpr()),
+          exprWithCleanups(has(ignoringElidableConstructorCall(callExpr())))))),
+      LanguageMode::Cxx11OrLater));
+}
+
+TEST(Matcher, IgnoresElidableInReturn) {
+  auto matcher = expr(ignoringElidableConstructorCall(declRefExpr()));
+  EXPECT_TRUE(matches("struct H {};"
+                      "H f() {"
+                      "  H g;"
+                      "  return g;"
+                      "}",
+                      matcher, LanguageMode::Cxx11OrLater));
+  EXPECT_TRUE(notMatches("struct H {};"
+                         "H f() {"
+                         "  return H();"
+                         "}",
+                         matcher, LanguageMode::Cxx11OrLater));
+}
+
+TEST(Matcher, IgnoreElidableConstructorDoesNotMatchConstructors) {
+  EXPECT_TRUE(matches("struct H {};"
+                      "void f() {"
+                      "  H D;"
+                      "}",
+                      varDecl(hasInitializer(
+                          ignoringElidableConstructorCall(cxxConstructExpr()))),
+                      LanguageMode::Cxx11OrLater));
+}
+
+TEST(Matcher, IgnoresElidableDoesNotPreventMatches) {
+  EXPECT_TRUE(matches("void f() {"
+                      "  int D = 10;"
+                      "}",
+                      expr(ignoringElidableConstructorCall(integerLiteral())),
+                      LanguageMode::Cxx11OrLater));
+}
+
 TEST(Matcher, BindTheSameNameInAlternatives) {
   StatementMatcher matcher = anyOf(
     binaryOperator(hasOperatorName("+"),
@@ -914,10 +982,10 @@ TEST(isConstexpr, MatchesConstexprDeclarations) {
                       varDecl(hasName("foo"), isConstexpr())));
   EXPECT_TRUE(matches("constexpr int bar();",
                       functionDecl(hasName("bar"), isConstexpr())));
-  EXPECT_TRUE(matchesConditionally("void baz() { if constexpr(1 > 0) {} }",
-                                   ifStmt(isConstexpr()), true, "-std=c++17"));
-  EXPECT_TRUE(matchesConditionally("void baz() { if (1 > 0) {} }",
-                                   ifStmt(isConstexpr()), false, "-std=c++17"));
+  EXPECT_TRUE(matches("void baz() { if constexpr(1 > 0) {} }",
+                      ifStmt(isConstexpr()), LanguageMode::Cxx17OrLater));
+  EXPECT_TRUE(notMatches("void baz() { if (1 > 0) {} }", ifStmt(isConstexpr()),
+                         LanguageMode::Cxx17OrLater));
 }
 
 TEST(TemplateArgumentCountIs, Matches) {
diff --git a/clang/unittests/ASTMatchers/ASTMatchersTest.h b/clang/unittests/ASTMatchers/ASTMatchersTest.h
index 78c551f806f..745122a2819 100644
--- a/clang/unittests/ASTMatchers/ASTMatchersTest.h
+++ b/clang/unittests/ASTMatchers/ASTMatchersTest.h
@@ -57,6 +57,17 @@ private:
   const std::unique_ptr<BoundNodesCallback> FindResultReviewer;
 };
 
+enum class LanguageMode {
+  Cxx11,
+  Cxx14,
+  Cxx17,
+  Cxx2a,
+  Cxx11OrLater,
+  Cxx14OrLater,
+  Cxx17OrLater,
+  Cxx2aOrLater
+};
+
 template <typename T>
 testing::AssertionResult matchesConditionally(
     const std::string &Code, const T &AMatcher, bool ExpectMatch,
@@ -116,14 +127,71 @@ testing::AssertionResult matchesConditionally(
 }
 
 template <typename T>
-testing::AssertionResult matches(const std::string &Code, const T &AMatcher) {
-  return matchesConditionally(Code, AMatcher, true, "-std=c++11");
+testing::AssertionResult
+matchesConditionally(const std::string &Code, const T &AMatcher,
+                     bool ExpectMatch, const LanguageMode &Mode) {
+  std::vector<LanguageMode> LangModes;
+  switch (Mode) {
+  case LanguageMode::Cxx11:
+  case LanguageMode::Cxx14:
+  case LanguageMode::Cxx17:
+  case LanguageMode::Cxx2a:
+    LangModes = {Mode};
+    break;
+  case LanguageMode::Cxx11OrLater:
+    LangModes = {LanguageMode::Cxx11, LanguageMode::Cxx14, LanguageMode::Cxx17,
+                 LanguageMode::Cxx2a};
+    break;
+  case LanguageMode::Cxx14OrLater:
+    LangModes = {LanguageMode::Cxx14, LanguageMode::Cxx17, LanguageMode::Cxx2a};
+    break;
+  case LanguageMode::Cxx17OrLater:
+    LangModes = {LanguageMode::Cxx17, LanguageMode::Cxx2a};
+    break;
+  case LanguageMode::Cxx2aOrLater:
+    LangModes = {LanguageMode::Cxx2a};
+  }
+
+  for (auto Mode : LangModes) {
+    std::string LangModeArg;
+    switch (Mode) {
+    case LanguageMode::Cxx11:
+      LangModeArg = "-std=c++11";
+      break;
+    case LanguageMode::Cxx14:
+      LangModeArg = "-std=c++14";
+      break;
+    case LanguageMode::Cxx17:
+      LangModeArg = "-std=c++17";
+      break;
+    case LanguageMode::Cxx2a:
+      LangModeArg = "-std=c++2a";
+      break;
+    default:
+      llvm_unreachable("Invalid language mode");
+    }
+
+    auto Result =
+        matchesConditionally(Code, AMatcher, ExpectMatch, LangModeArg);
+    if (!Result)
+      return Result;
+  }
+
+  return testing::AssertionSuccess();
+}
+
+template <typename T>
+testing::AssertionResult
+matches(const std::string &Code, const T &AMatcher,
+        const LanguageMode &Mode = LanguageMode::Cxx11) {
+  return matchesConditionally(Code, AMatcher, true, Mode);
 }
 
 template <typename T>
-testing::AssertionResult notMatches(const std::string &Code,
-                                    const T &AMatcher) {
-  return matchesConditionally(Code, AMatcher, false, "-std=c++11");
+testing::AssertionResult
+notMatches(const std::string &Code, const T &AMatcher,
+           const LanguageMode &Mode = LanguageMode::Cxx11) {
+  return matchesConditionally(Code, AMatcher, false, Mode);
 }
 
 template <typename T>