When we see a '<' operator, check whether it's a probable typo for a template-id.

The heuristic that we use here is:
 * the left-hand side must be a simple identifier or a class member access
 * the right-hand side must be '<' followed by either a '>' or by a type-id that
   cannot be an expression (in particular, not followed by '(' or '{')
 * there is a '>' token matching the '<' token

The second condition guarantees the expression would otherwise be ill-formed.

If we're confident that the user intended the name before the '<' to be
interpreted as a template, diagnose the fact that we didn't interpret it
that way, rather than diagnosing that the template arguments are not valid
expressions.

llvm-svn: 302615

1 files changed, 43 insertions, 0 deletions

diff --git a/clang/test/SemaTemplate/typo-template-name.cpp b/clang/test/SemaTemplate/typo-template-name.cpp
new file mode 100644
index 00000000000..fe5201a8e26
--- /dev/null
+++ b/clang/test/SemaTemplate/typo-template-name.cpp
@@ -0,0 +1,43 @@
+// RUN: %clang_cc1 -std=c++1z %s -verify -Wno-unused
+
+namespace InExpr {
+  namespace A {
+    void typo_first_a(); // expected-note {{found}}
+    template<typename T> void typo_first_b(); // expected-note 2{{declared here}}
+  }
+  void testA() { A::typo_first_a<int>(); } // expected-error {{'typo_first_a' does not name a template but is followed by template arguments; did you mean 'typo_first_b'?}}
+
+  namespace B {
+    void typo_first_b(); // expected-note {{found}}
+  }
+  void testB() { B::typo_first_b<int>(); } // expected-error {{'typo_first_b' does not name a template but is followed by template arguments; did you mean 'A::typo_first_b'?}}
+
+  struct Base {
+    template<typename T> static void foo(); // expected-note 4{{declared here}}
+    int n;
+  };
+  struct Derived : Base {
+    void foo(); // expected-note {{found}}
+  };
+  // We probably don't want to suggest correcting to .Base::foo<int>
+  void testMember() { Derived().foo<int>(); } // expected-error-re {{does not name a template but is followed by template arguments{{$}}}}
+
+  struct Derived2 : Base {
+    void goo(); // expected-note {{found}}
+  };
+  void testMember2() { Derived2().goo<int>(); } // expected-error {{member 'goo' of 'InExpr::Derived2' is not a template; did you mean 'foo'?}}
+
+  void no_correction() {
+    int foo; // expected-note 3{{found}}
+
+    foo<int>(); // expected-error {{'foo' does not name a template but is followed by template arguments; did you mean 'Base::foo'?}}
+    foo<>(); // expected-error {{'foo' does not name a template but is followed by template arguments; did you mean 'Base::foo'?}}
+    foo<Base *>(); // expected-error {{'foo' does not name a template but is followed by template arguments; did you mean 'Base::foo'?}}
+
+    // These are valid expressions.
+    foo<foo; // expected-warning {{self-comparison}}
+    foo<int()>(0);
+    foo<int(), true>(false);
+    foo<Base{}.n;
+  }
+}