[clang][ASTMatcher] Handle variable templates in isInstantiated and isInTemplateInstantiation matchers (#110666)

Fix `isInstantiated` and `isInTemplateInstantiation` matchers, so they
return true for instantiations of variable templates, and any
declaration in statements contained in such instantiations.

Author: frederic-tingaud-sonarsource

clang/docs/ReleaseNotes.rst

@@ -745,6 +745,8 @@ AST Matchers
 
 - Fixed a crash when traverse lambda expr with invalid captures. (#GH106444)
 
+- Fixed ``isInstantiated`` and ``isInTemplateInstantiation`` to also match for variable templates. (#GH110666)
+
 - Ensure ``hasName`` matches template specializations across inline namespaces,
   making `matchesNodeFullSlow` and `matchesNodeFullFast` consistent.
 

clang/include/clang/ASTMatchers/ASTMatchers.h

@@ -6750,7 +6750,8 @@ AST_POLYMORPHIC_MATCHER(isTemplateInstantiation,
 ///   matches 'A(int) {...};' and 'A(unsigned) {...}'.
 AST_MATCHER_FUNCTION(internal::Matcher<Decl>, isInstantiated) {
   auto IsInstantiation = decl(anyOf(cxxRecordDecl(isTemplateInstantiation()),
-                                    functionDecl(isTemplateInstantiation())));
+                                    functionDecl(isTemplateInstantiation()),
+                                    varDecl(isTemplateInstantiation())));
   return decl(anyOf(IsInstantiation, hasAncestor(IsInstantiation)));
 }
 
@@ -6769,9 +6770,9 @@ AST_MATCHER_FUNCTION(internal::Matcher<Decl>, isInstantiated) {
 ///   will NOT match j += 42; as it's shared between the template definition and
 ///   instantiation.
 AST_MATCHER_FUNCTION(internal::Matcher<Stmt>, isInTemplateInstantiation) {
-  return stmt(
-      hasAncestor(decl(anyOf(cxxRecordDecl(isTemplateInstantiation()),
-                             functionDecl(isTemplateInstantiation())))));
+  return stmt(hasAncestor(decl(anyOf(cxxRecordDecl(isTemplateInstantiation()),
+                                     functionDecl(isTemplateInstantiation()),
+                                     varDecl(isTemplateInstantiation())))));
 }
 
 /// Matches explicit template specializations of function, class, or

clang/unittests/ASTMatchers/ASTMatchersNarrowingTest.cpp

@@ -3342,6 +3342,45 @@ TEST_P(ASTMatchersTest,
                          declStmt(isInTemplateInstantiation())));
 }
 
+TEST_P(ASTMatchersTest, IsInstantiated_MatchesVariableInstantiation) {
+  if (!GetParam().isCXX14OrLater()) {
+    return;
+  }
+
+  EXPECT_TRUE(matches("template<typename T> int V = 10; void x() { V<int>; }",
+                      varDecl(isInstantiated())));
+}
+
+TEST_P(ASTMatchersTest, IsInstantiated_NotMatchesVariableDefinition) {
+  if (!GetParam().isCXX14OrLater()) {
+    return;
+  }
+
+  EXPECT_TRUE(notMatches("template<typename T> int V = 10;",
+                         varDecl(isInstantiated())));
+}
+
+TEST_P(ASTMatchersTest,
+       IsInTemplateInstantiation_MatchesVariableInstantiationStmt) {
+  if (!GetParam().isCXX14OrLater()) {
+    return;
+  }
+
+  EXPECT_TRUE(matches(
+      "template<typename T> auto V = []() { T i; }; void x() { V<int>(); }",
+      declStmt(isInTemplateInstantiation())));
+}
+
+TEST_P(ASTMatchersTest,
+       IsInTemplateInstantiation_NotMatchesVariableDefinitionStmt) {
+  if (!GetParam().isCXX14OrLater()) {
+    return;
+  }
+
+  EXPECT_TRUE(notMatches("template<typename T> auto V = []() { T i; };",
+                         declStmt(isInTemplateInstantiation())));
+}
+
 TEST_P(ASTMatchersTest, IsInTemplateInstantiation_Sharing) {
   if (!GetParam().isCXX()) {
     return;