[AstMatcher]templateArgumentCountIs support FunctionDecl (#130416)

`hasTemplateArgument` and `templateArgumentCountIs` are always used together. It is more convenient to make then support `FunctionDecl`.

Author: HerrCai0907

clang/docs/LibASTMatchersReference.html

@@ -4108,8 +4108,14 @@ <h2 id="narrowing-matchers">Narrowing Matchers</h2>
 Given
   template&lt;typename T&gt; struct C {};
   C&lt;int&gt; c;
+  template&lt;typename T&gt; void f() {}
+  void func() { f&lt;int&gt;(); };
+
 classTemplateSpecializationDecl(templateArgumentCountIs(1))
   matches C&lt;int&gt;.
+
+functionDecl(templateArgumentCountIs(1))
+  matches f&lt;int&gt;();
 </pre></td></tr>
 
 
@@ -4833,6 +4839,23 @@ <h2 id="narrowing-matchers">Narrowing Matchers</h2>
 </pre></td></tr>
 
 
+<tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1FunctionDecl.html">FunctionDecl</a>&gt;</td><td class="name" onclick="toggle('templateArgumentCountIs2')"><a name="templateArgumentCountIs2Anchor">templateArgumentCountIs</a></td><td>unsigned N</td></tr>
+<tr><td colspan="4" class="doc" id="templateArgumentCountIs2"><pre>Matches if the number of template arguments equals N.
+
+Given
+  template&lt;typename T&gt; struct C {};
+  C&lt;int&gt; c;
+  template&lt;typename T&gt; void f() {}
+  void func() { f&lt;int&gt;(); };
+
+classTemplateSpecializationDecl(templateArgumentCountIs(1))
+  matches C&lt;int&gt;.
+
+functionDecl(templateArgumentCountIs(1))
+  matches f&lt;int&gt;();
+</pre></td></tr>
+
+
 <tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1FunctionProtoType.html">FunctionProtoType</a>&gt;</td><td class="name" onclick="toggle('hasDynamicExceptionSpec1')"><a name="hasDynamicExceptionSpec1Anchor">hasDynamicExceptionSpec</a></td><td></td></tr>
 <tr><td colspan="4" class="doc" id="hasDynamicExceptionSpec1"><pre>Matches functions that have a dynamic exception specification.
 
@@ -5783,14 +5806,20 @@ <h2 id="narrowing-matchers">Narrowing Matchers</h2>
 </pre></td></tr>
 
 
-<tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1TemplateSpecializationType.html">TemplateSpecializationType</a>&gt;</td><td class="name" onclick="toggle('templateArgumentCountIs1')"><a name="templateArgumentCountIs1Anchor">templateArgumentCountIs</a></td><td>unsigned N</td></tr>
-<tr><td colspan="4" class="doc" id="templateArgumentCountIs1"><pre>Matches if the number of template arguments equals N.
+<tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1TemplateSpecializationType.html">TemplateSpecializationType</a>&gt;</td><td class="name" onclick="toggle('templateArgumentCountIs3')"><a name="templateArgumentCountIs3Anchor">templateArgumentCountIs</a></td><td>unsigned N</td></tr>
+<tr><td colspan="4" class="doc" id="templateArgumentCountIs3"><pre>Matches if the number of template arguments equals N.
 
 Given
   template&lt;typename T&gt; struct C {};
   C&lt;int&gt; c;
+  template&lt;typename T&gt; void f() {}
+  void func() { f&lt;int&gt;(); };
+
 classTemplateSpecializationDecl(templateArgumentCountIs(1))
   matches C&lt;int&gt;.
+
+functionDecl(templateArgumentCountIs(1))
+  matches f&lt;int&gt;();
 </pre></td></tr>
 
 
@@ -6219,6 +6248,23 @@ <h2 id="narrowing-matchers">Narrowing Matchers</h2>
 Usable as: 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_1VarDecl.html">VarDecl</a>&gt;, Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1CXXRecordDecl.html">CXXRecordDecl</a>&gt;
 </pre></td></tr>
 
+
+<tr><td>Matcher&lt;<a href="https://clang.llvm.org/doxygen/classclang_1_1VarTemplateSpecializationDecl.html">VarTemplateSpecializationDecl</a>&gt;</td><td class="name" onclick="toggle('templateArgumentCountIs1')"><a name="templateArgumentCountIs1Anchor">templateArgumentCountIs</a></td><td>unsigned N</td></tr>
+<tr><td colspan="4" class="doc" id="templateArgumentCountIs1"><pre>Matches if the number of template arguments equals N.
+
+Given
+  template&lt;typename T&gt; struct C {};
+  C&lt;int&gt; c;
+  template&lt;typename T&gt; void f() {}
+  void func() { f&lt;int&gt;(); };
+
+classTemplateSpecializationDecl(templateArgumentCountIs(1))
+  matches C&lt;int&gt;.
+
+functionDecl(templateArgumentCountIs(1))
+  matches f&lt;int&gt;();
+</pre></td></tr>
+
 <!--END_NARROWING_MATCHERS -->
 </table>
 

clang/docs/ReleaseNotes.rst

@@ -397,6 +397,8 @@ AST Matchers
 ------------
 
 - Ensure ``isDerivedFrom`` matches the correct base in case more than one alias exists.
+- Extend ``templateArgumentCountIs`` to support function and variable template
+  specialization.
 
 clang-format
 ------------

clang/include/clang/ASTMatchers/ASTMatchers.h

@@ -1084,12 +1084,19 @@ AST_POLYMORPHIC_MATCHER_P2(
 /// \code
 ///   template<typename T> struct C {};
 ///   C<int> c;
+///   template<typename T> void f() {}
+///   void func() { f<int>(); };
 /// \endcode
+///
 /// classTemplateSpecializationDecl(templateArgumentCountIs(1))
 ///   matches C<int>.
+///
+/// functionDecl(templateArgumentCountIs(1))
+///   matches f<int>();
 AST_POLYMORPHIC_MATCHER_P(
     templateArgumentCountIs,
     AST_POLYMORPHIC_SUPPORTED_TYPES(ClassTemplateSpecializationDecl,
+                                    VarTemplateSpecializationDecl, FunctionDecl,
                                     TemplateSpecializationType),
     unsigned, N) {
   return internal::getTemplateSpecializationArgs(Node).size() == N;

clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp

@@ -2028,6 +2028,13 @@ TEST_P(ASTMatchersTest, TemplateArgumentCountIs) {
   EXPECT_TRUE(
       notMatches("template<typename T> struct C {}; C<int> c;",
                  templateSpecializationType(templateArgumentCountIs(2))));
+
+  const char *FuncTemplateCode =
+      "template<typename T> T f(); auto v = f<int>();";
+  EXPECT_TRUE(
+      matches(FuncTemplateCode, functionDecl(templateArgumentCountIs(1))));
+  EXPECT_TRUE(
+      notMatches(FuncTemplateCode, functionDecl(templateArgumentCountIs(2))));
 }
 
 TEST_P(ASTMatchersTest, IsIntegral) {