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C++ PATCH for c++/79056, C++17 ICE with invalid template-id

Message ID CADzB+2mp0t4NxNSQmWeZnW19u_cL6an7evXSonc0Kmt-UT+Xog@mail.gmail.com
State New
Headers show

Commit Message

Jason Merrill June 23, 2017, 11:30 p.m. UTC 
In this testcase, in C++17 mode after parsing the template-id fails,
we try to treat the template-name as a class template deduction
placeholder, producing an auto type, and then we try to take its
TREE_TYPE when calling cp_parser_check_for_invalid_type_id, which
doesn't work because it's a type, not a TYPE_DECL.  Fixed by removing
the TREE_TYPE and adjusting cp_parser_check_for_invalid_type_id to
handle TYPE_DECL.

Really we shouldn't be creating a deduction placeholder in the first
place when the template name is followed by <, but that distinction
shouldn't affect well-formed code since we try to parse a template-id
first.

I still want to improve our handling of parse errors in template-ids;
we never actually diagnose the syntax error here because it's
swallowed by tentative parsing, we just say "argument 1 is invalid".

Tested x86_64-pc-linux-gnu, applying to trunk.
commit bbea244e8042460d49970b7fffce13f79e58d8e9
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Jun 20 15:32:06 2017 -0400

            PR c++/79056 - C++17 ICE with invalid template syntax.
    
            * parser.c (cp_parser_simple_type_specifier): Don't assume that type
            is a TYPE_DECL.
            (cp_parser_check_for_invalid_template_id): Handle TYPE_DECL.
            * pt.c (template_placeholder_p): New.
            * cp-tree.h: Declare it.
diff mbox

Patch

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 40c113b..33dde15 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6413,6 +6413,7 @@  extern void check_template_variable		(tree);
 extern tree make_auto				(void);
 extern tree make_decltype_auto			(void);
 extern tree make_template_placeholder		(tree);
+extern bool template_placeholder_p		(tree);
 extern tree do_auto_deduction                   (tree, tree, tree);
 extern tree do_auto_deduction                   (tree, tree, tree,
                                                  tsubst_flags_t,
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index ddb1cf3..97cd923 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -2983,7 +2983,9 @@  cp_parser_check_for_invalid_template_id (cp_parser* parser,
 
   if (cp_lexer_next_token_is (parser->lexer, CPP_LESS))
     {
-      if (TYPE_P (type))
+      if (TREE_CODE (type) == TYPE_DECL)
+	type = TREE_TYPE (type);
+      if (TYPE_P (type) && !template_placeholder_p (type))
 	error_at (location, "%qT is not a template", type);
       else if (identifier_p (type))
 	{
@@ -17060,7 +17062,7 @@  cp_parser_simple_type_specifier (cp_parser* parser,
       /* There is no valid C++ program where a non-template type is
 	 followed by a "<".  That usually indicates that the user
 	 thought that the type was a template.  */
-      cp_parser_check_for_invalid_template_id (parser, TREE_TYPE (type),
+      cp_parser_check_for_invalid_template_id (parser, type,
 					       none_type,
 					       token->location);
     }
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index fba7fb1..392fba0 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -24799,6 +24799,14 @@  make_template_placeholder (tree tmpl)
   return t;
 }
 
+/* True iff T is a C++17 class template deduction placeholder.  */
+
+bool
+template_placeholder_p (tree t)
+{
+  return is_auto (t) && CLASS_PLACEHOLDER_TEMPLATE (t);
+}
+
 /* Make a "constrained auto" type-specifier. This is an
    auto type with constraints that must be associated after
    deduction.  The constraint is formed from the given
diff --git a/gcc/testsuite/g++.dg/parse/template28.C b/gcc/testsuite/g++.dg/parse/template28.C
new file mode 100644
index 0000000..6868bc8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/parse/template28.C
@@ -0,0 +1,10 @@ 
+// PR c++/79056
+
+template<class> struct A {};
+
+template<class T> void foo(A<T>=A<T>()) {} // { dg-error "" }
+
+void bar()
+{
+  foo(A<int>());		// { dg-error "" }
+}