[PATCH] D75556: [AST Matchers] Restrict `optionally` matcher to a single argument.

[Yitzhak Mandelbaum via Phabricator via cfe-commits]

ymandel created this revision.
ymandel added reviewers: sbenza, aaron.ballman.
Herald added a project: clang.

Currently, `optionally` can take multiple arguments, which commits it to a
particular strategy for those arguments (in this case, "for each"). We limit the
matcher to a single argument, which avoids any potential confusion and
simplifies the implementation. The user can retrieve multiple-argument
optionality, by explicitly using the desired operator (like `forEach`, `anyOf`,
`allOf`, etc.) with all children wrapped in `optionally`.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D75556

Files:
  clang/include/clang/ASTMatchers/ASTMatchers.h
  clang/lib/ASTMatchers/ASTMatchersInternal.cpp
  clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp


Index: clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
===================================================================
--- clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
+++ clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp
@@ -2007,9 +2007,8 @@
 TEST(Optionally, SubmatchersDoNotMatch) {
   EXPECT_TRUE(matchAndVerifyResultFalse(
       "class A { int a; int b; };",
-      recordDecl(optionally(has(fieldDecl(hasName("c")).bind("v")),
-                            has(fieldDecl(hasName("d")).bind("v")))),
-      std::make_unique<VerifyIdIsBoundTo<FieldDecl>>("v")));
+      recordDecl(optionally(has(fieldDecl(hasName("c")).bind("c")))),
+      std::make_unique<VerifyIdIsBoundTo<FieldDecl>>("c")));
 }
 
 // Regression test.
@@ -2028,14 +2027,8 @@
 TEST(Optionally, SubmatchersMatch) {
   EXPECT_TRUE(matchAndVerifyResultTrue(
       "class A { int a; int c; };",
-      recordDecl(optionally(has(fieldDecl(hasName("a")).bind("v")),
-                            has(fieldDecl(hasName("b")).bind("v")))),
-      std::make_unique<VerifyIdIsBoundTo<FieldDecl>>("v", 1)));
-  EXPECT_TRUE(matchAndVerifyResultTrue(
-      "class A { int c; int b; };",
-      recordDecl(optionally(has(fieldDecl(hasName("c")).bind("v")),
-                            has(fieldDecl(hasName("b")).bind("v")))),
-      std::make_unique<VerifyIdIsBoundTo<FieldDecl>>("v", 2)));
+      recordDecl(optionally(has(fieldDecl(hasName("a")).bind("v")))),
+      std::make_unique<VerifyIdIsBoundTo<FieldDecl>>("v")));
 }
 
 TEST(IsTemplateInstantiation, MatchesImplicitClassTemplateInstantiation) {
Index: clang/lib/ASTMatchers/ASTMatchersInternal.cpp
===================================================================
--- clang/lib/ASTMatchers/ASTMatchersInternal.cpp
+++ clang/lib/ASTMatchers/ASTMatchersInternal.cpp
@@ -346,18 +346,11 @@
                                 ASTMatchFinder *Finder,
                                 BoundNodesTreeBuilder *Builder,
                                 ArrayRef<DynTypedMatcher> InnerMatchers) {
-  BoundNodesTreeBuilder Result;
-  bool Matched = false;
-  for (const DynTypedMatcher &InnerMatcher : InnerMatchers) {
-    BoundNodesTreeBuilder BuilderInner(*Builder);
-    if (InnerMatcher.matches(DynNode, Finder, &BuilderInner)) {
-      Matched = true;
-      Result.addMatch(BuilderInner);
-    }
-  }
-  // If there were no matches, we can't assign to `*Builder`; we'd (incorrectly)
-  // clear it because `Result` is empty.
-  if (Matched)
+  if (InnerMatchers.size() != 1)
+    return false;
+
+  BoundNodesTreeBuilder Result(*Builder);
+  if (InnerMatchers[0].matches(DynNode, Finder, &Result))
     *Builder = std::move(Result);
   return true;
 }
@@ -859,9 +852,8 @@
 const internal::VariadicOperatorMatcherFunc<
     2, std::numeric_limits<unsigned>::max()>
     allOf = {internal::DynTypedMatcher::VO_AllOf};
-const internal::VariadicOperatorMatcherFunc<
-    1, std::numeric_limits<unsigned>::max()>
-    optionally = {internal::DynTypedMatcher::VO_Optionally};
+const internal::VariadicOperatorMatcherFunc<1, 1> optionally = {
+    internal::DynTypedMatcher::VO_Optionally};
 const internal::VariadicFunction<internal::Matcher<NamedDecl>, StringRef,
                                  internal::hasAnyNameFunc>
     hasAnyName = {};
Index: clang/include/clang/ASTMatchers/ASTMatchers.h
===================================================================
--- clang/include/clang/ASTMatchers/ASTMatchers.h
+++ clang/include/clang/ASTMatchers/ASTMatchers.h
@@ -2612,9 +2612,7 @@
 /// member named "bar" in that class.
 ///
 /// Usable as: Any Matcher
-extern const internal::VariadicOperatorMatcherFunc<
-    1, std::numeric_limits<unsigned>::max()>
-    optionally;
+extern const internal::VariadicOperatorMatcherFunc<1, 1> optionally;
 
 /// Matches sizeof (C99), alignof (C++11) and vec_step (OpenCL)
 ///


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