ASTMatchers: Add a matcher to detect whether a decl or stmt is inside a template instantiation.

[bkramer]

Summary

This is hoisted from clang-tidy where it's used everywhere. The implementation
is not particularly efficient right now, but there is no easy fix for that.

[klimek]

include/clang/ASTMatchers/ASTMatchers.h

2970–2982

Perhaps add comment that this will not match if the node itself is a template instantiation (so functionDecl(isInTemplateInstantiation()) will not match anything here).

I'd also add a comment about node sharing; for example, given
int j;
template<typename T> void A(T t) { T i; j += 42; int x; }

stmt(unless(isInTemplateInstnatiation()))

will not match j += 42 (because the template independent node is shared between the definition and the instantiations), but will match 'T i;' (with the dependent type), because the dependent nodes cannot be shared.
Funnily enough 'int x' *will* match (as will any further statement referencing x); I have no idea why the node cannot be shared, which is why node sharing always makes me feel cautious.

Of course:

stmt(isInTemplateInstnatiation())

will match all.

2980

Also matches the block '{ T i; }'.

[alexfh]

include/clang/ASTMatchers/ASTMatchers.h

2970–2982

Perhaps add comment that this will not match if the node itself is a template instantiation

Maybe add a separate version for decl, which will handle this? Something along the lines of:

auto IsInstantiation = decl(anyOf(recordDecl(isTemplateInstantiation()),
                                  functionDecl(isTemplateInstantiation())));
auto InnerMatcher = decl(anyOf(isInstantiation, hasAncestor(isInstantiation));

[bkramer]

Split into two matchers, one for Decl (also matches itself) and one for Stmt.
Update tests and document node sharing artifacts.

[alexfh]

include/clang/ASTMatchers/ASTMatchers.h

2970

I find this comment somewhat hard to understand. I'd say that this matches declarations that are template instantiations or are inside template instantiations.

2998

Did you mean isInTemplateInstantiation (here and below)?

lib/ASTMatchers/Dynamic/Registry.cpp

245

Why do you register only one matcher?

[bkramer]

Address review comments.

[klimek]

lg

Closed by commit rL217029 (authored by d0k).

include/clang/ASTMatchers/ASTMatchers.h

 AST_POLYMORPHIC_MATCHER(
     isTemplateInstantiation,
     AST_POLYMORPHIC_SUPPORTED_TYPES_3(FunctionDecl, VarDecl, CXXRecordDecl)) {
   return (Node.getTemplateSpecializationKind() == TSK_ImplicitInstantiation ||
           Node.getTemplateSpecializationKind() ==
           TSK_ExplicitInstantiationDefinition);
 }
 
+/// \brief Matches declarations or statements that are contained in a function
+/// or class template instantiation.
+///
+/// Given
+/// \code
+///   template<typename T> void A(T t) { T i; }
+///   A(0);
+///   A(0U);
+/// \endcode
+/// stmt(isInTemplateInstantiation())
+///   matches 'int i;' and 'unsigned i;'.
+///
+/// Usable as: Matcher<Decl>, Matcher<Stmt>
+AST_POLYMORPHIC_MATCHER(isInTemplateInstantiation,
+                        AST_POLYMORPHIC_SUPPORTED_TYPES_2(Decl, Stmt)) {
+  Matcher<NodeType> InnerMatcher =
+      hasAncestor(decl(anyOf(recordDecl(isTemplateInstantiation()),
+                             functionDecl(isTemplateInstantiation()))));
+  return InnerMatcher.matches(Node, Finder, Builder);
+}
+
 /// \brief Matches explicit template specializations of function, class, or
 /// static member variable template instantiations.
 ///
 /// Given
 /// \code
 ///   template<typename T> void A(T t) { }
 ///   template<> void A(int N) { }
 /// \endcode
 /// functionDecl(isExplicitTemplateSpecialization())
 ///   matches the specialization A<int>().
 ///
 /// Usable as: Matcher<FunctionDecl>, Matcher<VarDecl>, Matcher<CXXRecordDecl>
 AST_POLYMORPHIC_MATCHER(
     isExplicitTemplateSpecialization,
     AST_POLYMORPHIC_SUPPORTED_TYPES_3(FunctionDecl, VarDecl, CXXRecordDecl)) {
   return (Node.getTemplateSpecializationKind() == TSK_ExplicitSpecialization);

lib/ASTMatchers/Dynamic/Registry.cpp

RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER(isConstQualified);
   REGISTER_MATCHER(isDefinition);
   REGISTER_MATCHER(isDeleted);
   REGISTER_MATCHER(isExplicitTemplateSpecialization);
   REGISTER_MATCHER(isExpr);
   REGISTER_MATCHER(isExternC);
   REGISTER_MATCHER(isImplicit);
   REGISTER_MATCHER(isInteger);
+  REGISTER_MATCHER(isInTemplateInstantiation);
   REGISTER_MATCHER(isListInitialization);
   REGISTER_MATCHER(isOverride);
   REGISTER_MATCHER(isPrivate);
   REGISTER_MATCHER(isProtected);
   REGISTER_MATCHER(isPublic);
   REGISTER_MATCHER(isPure);
   REGISTER_MATCHER(isTemplateInstantiation);
   REGISTER_MATCHER(isVirtual);

unittests/ASTMatchers/ASTMatchersTest.cpp

 }
 
 TEST(IsTemplateInstantiation, DoesNotMatchNonTemplate) {
   EXPECT_TRUE(notMatches(
       "class A {}; class Y { A a; };",
       recordDecl(isTemplateInstantiation())));
 }
 
+TEST(IsInTemplateInstantiation, MatchesInstantiation) {
+  EXPECT_TRUE(
+      matches("template<typename T> class A { T i; }; class Y { A<int> a; };",
+              recordDecl(isInTemplateInstantiation())));
+}
+
+TEST(IsInTemplateInstantiation, NotMatchesDefinition) {
+  EXPECT_TRUE(notMatches("template<typename T> class A { T i; };",
+                         recordDecl(isInTemplateInstantiation())));
+}
+
+TEST(IsInTemplateInstantiation, MatchesInstantiationStmt) {
+  EXPECT_TRUE(matches("template<typename T> struct A { A() { T i; } };"
+                      "class Y { A<int> a; }; Y y;",
+                      declStmt(isInTemplateInstantiation())));
+}
+
+TEST(IsInTemplateInstantiation, NotMatchesDefinitionStmt) {
+  EXPECT_TRUE(notMatches("template<typename T> struct A { void x() { T i; } };",
+                         declStmt(isInTemplateInstantiation())));
+}
+
+TEST(IsInTemplateInstantiation, MatchesFunctionInstantiation) {
+  EXPECT_TRUE(
+      matches("template<typename T> void A(T t) { T i; } void x() { A(0); }",
+              varDecl(isInTemplateInstantiation())));
+}
+
+TEST(IsInTemplateInstantiation, NotMatchesFunctionDefinition) {
+  EXPECT_TRUE(notMatches("template<typename T> void A(T t) { T i; }",
+                         varDecl(isInTemplateInstantiation())));
+}
+
+TEST(IsInTemplateInstantiation, MatchesFunctionInstantiationStmt) {
+  EXPECT_TRUE(
+      matches("template<typename T> void A(T t) { T i; } void x() { A(0); }",
+              declStmt(isInTemplateInstantiation())));
+}
+
+TEST(IsInTemplateInstantiation, NotMatchesFunctionDefinitionStmt) {
+  EXPECT_TRUE(notMatches("template<typename T> void A(T t) { T i; }",
+                         declStmt(isInTemplateInstantiation())));
+}
+
 TEST(IsExplicitTemplateSpecialization,
      DoesNotMatchPrimaryTemplate) {
   EXPECT_TRUE(notMatches(
       "template <typename T> class X {};",
       recordDecl(isExplicitTemplateSpecialization())));
   EXPECT_TRUE(notMatches(
       "template <typename T> void f(T t);",
       functionDecl(isExplicitTemplateSpecialization())));