From: Marek Polacek <polacek@redhat.com>
Date: Tue, 10 Sep 2019 02:29:13 +0000 (+0000)
Subject: PR c++/84374 - diagnose invalid uses of decltype(auto).
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=77df40e8127ec4f62c01c15f2d6f76d995424863;p=gcc.git

PR c++/84374 - diagnose invalid uses of decltype(auto).

	* decl.c (grokdeclarator): Diagnose wrong usage of decltype(auto) in
	a function declaration.

	* g++.dg/cpp1y/auto-fn57.C: New test.

From-SVN: r275557
---

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 48582cea2f2..2b98a06d586 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2019-09-09  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/84374 - diagnose invalid uses of decltype(auto).
+	* decl.c (grokdeclarator): Diagnose wrong usage of decltype(auto) in
+	a function declaration.
+
 2019-09-06  Nathan Sidwell  <nathan@acm.org>
 
 	PR c++/91125
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 88e2c3beb2b..dfcd7b16e6e 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -11681,6 +11681,16 @@ grokdeclarator (const cp_declarator *declarator,
 			  "allowed");
 		return error_mark_node;
 	      }
+	    /* Only plain decltype(auto) is allowed.  */
+	    if (tree a = type_uses_auto (type))
+	      {
+		if (AUTO_IS_DECLTYPE (a) && a != type)
+		  {
+		    error_at (typespec_loc, "%qT as type rather than "
+			      "plain %<decltype(auto)%>", type);
+		    return error_mark_node;
+		  }
+	      }
 
 	    if (ctype == NULL_TREE
 		&& decl_context == FIELD
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 3d4ada85579..f738a231358 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2019-09-09  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/84374 - diagnose invalid uses of decltype(auto).
+	* g++.dg/cpp1y/auto-fn57.C: New test.
+
 2019-09-09  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* gcc.target/powerpc/rlwinm-0.c: Adjust expected instruction counts.
diff --git a/gcc/testsuite/g++.dg/cpp1y/auto-fn57.C b/gcc/testsuite/g++.dg/cpp1y/auto-fn57.C
new file mode 100644
index 00000000000..e58df187df5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/auto-fn57.C
@@ -0,0 +1,18 @@
+// PR c++/84374 - diagnose invalid uses of decltype(auto).
+// { dg-do compile { target c++14 } }
+
+auto l = [](auto* r)->decltype(auto)* { return r; }; // { dg-error "as type rather than plain" }
+auto m = [](auto* r)->decltype(auto)& { return *r; }; // { dg-error "as type rather than plain" }
+
+decltype(auto)* f(); // { dg-error "as type rather than plain" }
+decltype(auto)& f2(); // { dg-error "as type rather than plain" }
+decltype(auto)* f3() { return 42; } // { dg-error "as type rather than plain" }
+decltype(auto)& f4() { return 42; } // { dg-error "as type rather than plain" }
+
+
+class C {
+  decltype(auto)* g(); // { dg-error "as type rather than plain" }
+  decltype(auto)& g2(); // { dg-error "as type rather than plain" }
+  decltype(auto)* g3() { } // { dg-error "as type rather than plain" }
+  decltype(auto)& g4() { } // { dg-error "as type rather than plain" }
+};