* C++ PATCH for c++/84374 - diagnose invalid uses of decltype(auto)
@ 2019-09-08 16:47 Marek Polacek
2019-09-09 21:00 ` Jason Merrill
0 siblings, 1 reply; 4+ messages in thread
From: Marek Polacek @ 2019-09-08 16:47 UTC (permalink / raw)
To: GCC Patches, Jason Merrill
[dcl.type.auto.deduct]/5 "If the placeholder-type-specifier is of the
form type-constraintopt decltype(auto), T shall be the placeholder alone."
So, only plain decltype(auto) is allowed. But we aren't diagnosing it in
function declarations, because do_auto_deduction is never called for those.
Bootstrapped/regtested on x86_64-linux, ok for trunk?
2019-09-08 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.
* g++.dg/cpp1y/auto-fn57.C: New test.
diff --git gcc/cp/decl.c gcc/cp/decl.c
index 88e2c3beb2b..b1777730934 100644
--- gcc/cp/decl.c
+++ gcc/cp/decl.c
@@ -11560,6 +11560,14 @@ grokdeclarator (const cp_declarator *declarator,
"cannot have deduced return type");
virtualp = false;
}
+ else if (is_auto (auto_node)
+ && AUTO_IS_DECLTYPE (auto_node)
+ && type != auto_node)
+ {
+ error_at (typespec_loc, "%qT as type rather than "
+ "plain %<decltype(auto)%>", type);
+ return error_mark_node;
+ }
}
else if (!is_auto (type) && sfk != sfk_conversion)
{
@@ -11580,6 +11588,16 @@ grokdeclarator (const cp_declarator *declarator,
"invalid use of %<decltype(auto)%>");
return error_mark_node;
}
+ else if (tree a = type_uses_auto (late_return_type))
+ {
+ if (AUTO_IS_DECLTYPE (a) && a != late_return_type)
+ {
+ error_at (typespec_loc, "%qT as type rather than "
+ "plain %<decltype(auto)%>",
+ late_return_type);
+ return error_mark_node;
+ }
+ }
tree tmpl = CLASS_PLACEHOLDER_TEMPLATE (auto_node);
if (!tmpl)
if (tree late_auto = type_uses_auto (late_return_type))
diff --git gcc/testsuite/g++.dg/cpp1y/auto-fn57.C gcc/testsuite/g++.dg/cpp1y/auto-fn57.C
new file mode 100644
index 00000000000..e58df187df5
--- /dev/null
+++ 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" }
+};
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: C++ PATCH for c++/84374 - diagnose invalid uses of decltype(auto)
2019-09-08 16:47 C++ PATCH for c++/84374 - diagnose invalid uses of decltype(auto) Marek Polacek
@ 2019-09-09 21:00 ` Jason Merrill
2019-09-10 0:04 ` Marek Polacek
0 siblings, 1 reply; 4+ messages in thread
From: Jason Merrill @ 2019-09-09 21:00 UTC (permalink / raw)
To: Marek Polacek, GCC Patches
On 9/8/19 11:47 AM, Marek Polacek wrote:
> [dcl.type.auto.deduct]/5 "If the placeholder-type-specifier is of the
> form type-constraintopt decltype(auto), T shall be the placeholder alone."
>
> So, only plain decltype(auto) is allowed. But we aren't diagnosing it in
> function declarations, because do_auto_deduction is never called for those.
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
>
> 2019-09-08 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.
>
> * g++.dg/cpp1y/auto-fn57.C: New test.
>
> diff --git gcc/cp/decl.c gcc/cp/decl.c
> index 88e2c3beb2b..b1777730934 100644
> --- gcc/cp/decl.c
> +++ gcc/cp/decl.c
> @@ -11560,6 +11560,14 @@ grokdeclarator (const cp_declarator *declarator,
> "cannot have deduced return type");
> virtualp = false;
> }
> + else if (is_auto (auto_node)
> + && AUTO_IS_DECLTYPE (auto_node)
> + && type != auto_node)
> + {
> + error_at (typespec_loc, "%qT as type rather than "
> + "plain %<decltype(auto)%>", type);
> + return error_mark_node;
> + }
> }
> else if (!is_auto (type) && sfk != sfk_conversion)
> {
> @@ -11580,6 +11588,16 @@ grokdeclarator (const cp_declarator *declarator,
> "invalid use of %<decltype(auto)%>");
> return error_mark_node;
> }
> + else if (tree a = type_uses_auto (late_return_type))
> + {
> + if (AUTO_IS_DECLTYPE (a) && a != late_return_type)
> + {
> + error_at (typespec_loc, "%qT as type rather than "
> + "plain %<decltype(auto)%>",
> + late_return_type);
> + return error_mark_node;
> + }
> + }
Maybe check this in one place, after splice_late_return_type?
Jason
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: C++ PATCH for c++/84374 - diagnose invalid uses of decltype(auto)
2019-09-09 21:00 ` Jason Merrill
@ 2019-09-10 0:04 ` Marek Polacek
2019-09-10 2:17 ` Jason Merrill
0 siblings, 1 reply; 4+ messages in thread
From: Marek Polacek @ 2019-09-10 0:04 UTC (permalink / raw)
To: Jason Merrill; +Cc: GCC Patches
On Mon, Sep 09, 2019 at 04:59:57PM -0400, Jason Merrill wrote:
> Maybe check this in one place, after splice_late_return_type?
That works! So like this?
Bootstrapped/regtested on x86_64-linux, ok for trunk?
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.
* g++.dg/cpp1y/auto-fn57.C: New test.
diff --git gcc/cp/decl.c gcc/cp/decl.c
index 88e2c3beb2b..dfcd7b16e6e 100644
--- gcc/cp/decl.c
+++ 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 gcc/testsuite/g++.dg/cpp1y/auto-fn57.C gcc/testsuite/g++.dg/cpp1y/auto-fn57.C
new file mode 100644
index 00000000000..e58df187df5
--- /dev/null
+++ 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" }
+};
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: C++ PATCH for c++/84374 - diagnose invalid uses of decltype(auto)
2019-09-10 0:04 ` Marek Polacek
@ 2019-09-10 2:17 ` Jason Merrill
0 siblings, 0 replies; 4+ messages in thread
From: Jason Merrill @ 2019-09-10 2:17 UTC (permalink / raw)
To: Marek Polacek; +Cc: GCC Patches
On 9/9/19 7:03 PM, Marek Polacek wrote:
> On Mon, Sep 09, 2019 at 04:59:57PM -0400, Jason Merrill wrote:
>> Maybe check this in one place, after splice_late_return_type?
>
> That works! So like this?
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
OK, thanks.
Jason
^ permalink raw reply [flat|nested] 4+ messages in thread
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2019-09-08 16:47 C++ PATCH for c++/84374 - diagnose invalid uses of decltype(auto) Marek Polacek
2019-09-09 21:00 ` Jason Merrill
2019-09-10 0:04 ` Marek Polacek
2019-09-10 2:17 ` Jason Merrill
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