| Message ID | 20190908164709.GF14737@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | C++ PATCH for c++/84374 - diagnose invalid uses of decltype(auto) | expand |
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
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" }
+};
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
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" } +};