[PATCH] D78139: [clang-tidy] modernize-use-using: Fix broken fixit with 'template' keyword

[Matthias Gehre via Phabricator via cfe-commits]

mgehre created this revision.
mgehre added reviewers: aaron.ballman, alexfh, hokein, njames93.
Herald added a subscriber: xazax.hun.
Herald added a project: clang.

Before this PR, `modernize-use-using` would transform the typedef in

  template <typename a> class TemplateKeyword {
    typedef typename a::template f<> e;
    typedef typename a::template f<>::d e2;
  };

into

  template <typename a> class TemplateKeyword {
    using d = typename a::b<>;
    using d2 = typename a::template a::b<>::c;
  };

The first one is missing the `template` keyword,
the second one has an extra `a::` scope. Both result
in compilation errors.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D78139

Files:
  clang-tools-extra/test/clang-tidy/checkers/modernize-use-using.cpp
  clang/lib/AST/NestedNameSpecifier.cpp
  clang/lib/AST/TypePrinter.cpp
  clang/test/CXX/expr/expr.prim/expr.prim.req/type-requirement.cpp


Index: clang/test/CXX/expr/expr.prim/expr.prim.req/type-requirement.cpp
===================================================================
--- clang/test/CXX/expr/expr.prim/expr.prim.req/type-requirement.cpp
+++ clang/test/CXX/expr/expr.prim/expr.prim.req/type-requirement.cpp
@@ -109,9 +109,9 @@
 struct G { template<typename T> static T temp; };
 
 template<typename T> requires requires { typename T::template temp<int>; }
-// expected-note at -1{{because 'typename T::temp<int>' would be invalid: type 'int' cannot be used prior to '::' because it has no members}}
-// expected-note at -2{{because 'typename T::temp<int>' would be invalid: no member named 'temp' in 'D'}}
-// expected-note at -3{{because 'typename T::temp<int>' would be invalid: template name refers to non-type template 'G::template temp'}}
+// expected-note at -1{{because 'typename T::template temp<int>' would be invalid: type 'int' cannot be used prior to '::' because it has no members}}
+// expected-note at -2{{because 'typename T::template temp<int>' would be invalid: no member named 'temp' in 'D'}}
+// expected-note at -3{{because 'typename T::template temp<int>' would be invalid: template name refers to non-type template 'G::template temp'}}
 struct r7 {};
 
 using r7i1 = r7<int>; // expected-error{{constraints not satisfied for class template 'r7' [with T = int]}}
Index: clang/lib/AST/TypePrinter.cpp
===================================================================
--- clang/lib/AST/TypePrinter.cpp
+++ clang/lib/AST/TypePrinter.cpp
@@ -1388,6 +1388,7 @@
 
   if (T->getQualifier())
     T->getQualifier()->print(OS, Policy);
+  OS << "template ";
   OS << T->getIdentifier()->getName();
   printTemplateArgumentList(OS, T->template_arguments(), Policy);
   spaceBeforePlaceHolder(OS);
Index: clang/lib/AST/NestedNameSpecifier.cpp
===================================================================
--- clang/lib/AST/NestedNameSpecifier.cpp
+++ clang/lib/AST/NestedNameSpecifier.cpp
@@ -308,6 +308,14 @@
       // nested-name-specifier.
       SpecType->getTemplateName().print(OS, InnerPolicy, true);
 
+      // Print the template argument list.
+      printTemplateArgumentList(OS, SpecType->template_arguments(),
+                                InnerPolicy);
+    } else if (const auto *SpecType =
+                   dyn_cast<DependentTemplateSpecializationType>(T)) {
+      // Print the template name without its corresponding
+      // nested-name-specifier.
+      OS << SpecType->getIdentifier()->getName();
       // Print the template argument list.
       printTemplateArgumentList(OS, SpecType->template_arguments(),
                                 InnerPolicy);
Index: clang-tools-extra/test/clang-tidy/checkers/modernize-use-using.cpp
===================================================================
--- clang-tools-extra/test/clang-tidy/checkers/modernize-use-using.cpp
+++ clang-tools-extra/test/clang-tidy/checkers/modernize-use-using.cpp
@@ -249,6 +249,17 @@
 // CHECK-MESSAGES: :[[@LINE-1]]:1: warning: use 'using' instead of 'typedef'
 // CHECK-FIXES: using Nested_t = TwoArgTemplate<TwoArgTemplate<int, Q<T{0 < 0}.b>>, S<(0 < 0), Q<b[0 < 0]>>>;
 
+template <typename a>
+class TemplateKeyword {
+  typedef typename a::template b<> d;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use 'using' instead of 'typedef'
+  // CHECK-FIXES: using d = typename a::template b<>;
+
+  typedef typename a::template b<>::c d2;
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: use 'using' instead of 'typedef'
+  // CHECK-FIXES: using d2 = typename a::template b<>::c;
+};
+
 template <typename... Args>
 class Variadic {};
 


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