[ASTMatchers] Add `isDirectInit` matcher.

[courbet]

Summary

To match variables that are direct-initialized.

[courbet]

fix ddoc

[courbet]

fix doc

[courbet]

Regenerate doc

[courbet]

ping

[aaron.ballman]

You also need to add the new matcher to Registry.cpp so it's usable from the dynamic matchers, and you should add a release note for the new matcher.

Are you planning to use this matcher in-tree for something? (We don't usually add new matchers until there's a need for them given how expensive AST matchers are on compile times.)

[courbet]

In D141925#4073385, @aaron.ballman wrote:

You also need to add the new matcher to Registry.cpp so it's usable from the dynamic matchers, and you should add a release note for the new matcher.

Thanks, will do.

(We don't usually add new matchers until there's a need for them given how expensive AST matchers are on compile times.)

Ah, that's too bad.

Are you planning to use this matcher in-tree for something?

I was going to use it out-of-tree but figured it's a nice thing to have as many matchers as possible available for common use. There's also always the use case of people using clang-query (typically through godbolt).

I can live with the matcher being out-of-tree though, so you decide :)

[courbet]

add matcher to registry and add release note

[aaron.ballman]

In D141925#4073405, @courbet wrote:

In D141925#4073385, @aaron.ballman wrote:

You also need to add the new matcher to Registry.cpp so it's usable from the dynamic matchers, and you should add a release note for the new matcher.

Thanks, will do.

(We don't usually add new matchers until there's a need for them given how expensive AST matchers are on compile times.)

Ah, that's too bad.

Are you planning to use this matcher in-tree for something?

I was going to use it out-of-tree but figured it's a nice thing to have as many matchers as possible available for common use. There's also always the use case of people using clang-query (typically through godbolt).

I can live with the matcher being out-of-tree though, so you decide :)

I'd say let's leave it off for now -- if we find an in-tree need at some point, we can definitely add it then.

clang/docs/LibASTMatchersReference.html

Example matches A, va, fa
   - (void)ma {}
   @end
 
 Usable as: Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1TagDecl.html">TagDecl</a>&gt;, Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1VarDecl.html">VarDecl</a>&gt;, Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1FunctionDecl.html">FunctionDecl</a>&gt;,
   Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1ObjCMethodDecl.html">ObjCMethodDecl</a>&gt;
 </pre></td></tr>
 
 
+<tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1VarDecl.html">VarDecl</a>&gt;</td><td class="name" onclick="toggle('isDirectInit0')"><a name="isDirectInit0Anchor">isDirectInit</a></td><td></td></tr>
+<tr><td colspan="4" class="doc" id="isDirectInit0"><pre>Matches a variable initializer that is a direct-initializer.
+
+Example matches i2 and i2, but not i1 or i4
+(matcher = varDecl(isStaticLocal()))
+void f() {
+  int i1 = 3;
+  int i2(3);
+  int i3{3};
+  int i4;
+}
+</pre></td></tr>
+
+
 <tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1VarDecl.html">VarDecl</a>&gt;</td><td class="name" onclick="toggle('isExceptionVariable0')"><a name="isExceptionVariable0Anchor">isExceptionVariable</a></td><td></td></tr>
 <tr><td colspan="4" class="doc" id="isExceptionVariable0"><pre>Matches a variable declaration that is an exception variable from
 a C++ catch block, or an Objective-C statement.
 
 Example matches x (matcher = varDecl(isExceptionVariable())
 void f(int y) {
   try {
   } catch (int x) {

clang/docs/ReleaseNotes.rst

 These are major changes to the build system that have happened since the 12.0.0
 release of Clang. Users of the build system should adjust accordingly.
 
 - ...
 
 AST Matchers
 ------------
 
-- ...
+- `isDirectInit` matches variables that are direct-initialized (`int i2(3);`,
+  but not `int i1 = 3;`).
 
 clang-format
 ------------
 
 - Option ``SpacesInLineCommentPrefix`` has been added to control the
   number of spaces in a line comments prefix.
 
 - Option ``SortIncludes`` has been updated from a ``bool`` to an

clang/include/clang/ASTMatchers/ASTMatchers.h

 AST_MATCHER_P(
     VarDecl, hasInitializer, internal::Matcher<Expr>,
     InnerMatcher) {
   const Expr *Initializer = Node.getAnyInitializer();
   return (Initializer != nullptr &&
           InnerMatcher.matches(*Initializer, Finder, Builder));
 }
 
+/// \brief Matches a variable initializer that is a direct-initializer.
+///
+/// Example matches i2 and i2, but not i1 or i4
+/// (matcher = varDecl(isStaticLocal()))
+/// \code
+/// void f() {
+///   int i1 = 3;
+///   int i2(3);
+///   int i3{3};
+///   int i4;
+/// }
+/// \endcode
+AST_MATCHER(VarDecl, isDirectInit) {
+  return Node.isDirectInit();
+}
+
 /// \brief Matches a static variable with local scope.
 ///
 /// Example matches y (matcher = varDecl(isStaticLocal()))
 /// \code
 /// void f() {
 ///   int x;
 ///   static int y;
 /// }

clang/lib/ASTMatchers/Dynamic/Registry.cpp

RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER(isConstexpr);
   REGISTER_MATCHER(isCopyAssignmentOperator);
   REGISTER_MATCHER(isCopyConstructor);
   REGISTER_MATCHER(isDefaultConstructor);
   REGISTER_MATCHER(isDefaulted);
   REGISTER_MATCHER(isDefinition);
   REGISTER_MATCHER(isDelegatingConstructor);
   REGISTER_MATCHER(isDeleted);
+  REGISTER_MATCHER(isDirectInit);
   REGISTER_MATCHER(isEnum);
   REGISTER_MATCHER(isExceptionVariable);
   REGISTER_MATCHER(isExpandedFromMacro);
   REGISTER_MATCHER(isExpansionInMainFile);
   REGISTER_MATCHER(isExpansionInSystemHeader);
   REGISTER_MATCHER(isExplicit);
   REGISTER_MATCHER(isExplicitTemplateSpecialization);
   REGISTER_MATCHER(isExpr);

clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp

 TEST_P(ASTMatchersTest, IsStaticLocal) {
   auto M = varDecl(isStaticLocal());
   EXPECT_TRUE(matches("void f() { static int X; }", M));
   EXPECT_TRUE(notMatches("static int X;", M));
   EXPECT_TRUE(notMatches("void f() { int X; }", M));
   EXPECT_TRUE(notMatches("int X;", M));
 }
 
+TEST_P(ASTMatchersTest, IsDirectInit) {
+  auto M = varDecl(isDirectInit());
+  EXPECT_TRUE(notMatches("int i1 = 3;", M));
+  if (!GetParam().isCXX()) {
+    return;
+  }
+  EXPECT_TRUE(matches("int i2(3);", M));
+  if (!GetParam().isCXX11OrLater()) {
+    return;
+  }
+  EXPECT_TRUE(matches("int i3{3};", M));
+  EXPECT_TRUE(notMatches("int i4;", M));
+}
+
 TEST_P(ASTMatchersTest, StorageDuration) {
   StringRef T =
       "void f() { int x; static int y; } int a;static int b;extern int c;";
 
   EXPECT_TRUE(matches(T, varDecl(hasName("x"), hasAutomaticStorageDuration())));
   EXPECT_TRUE(
       notMatches(T, varDecl(hasName("y"), hasAutomaticStorageDuration())));
   EXPECT_TRUE(