PR c++/91678 - wrong error with decltype and location wrapper.

Compiling this testcase results in a bogus "invalid cast" error; this occurs
since the introduction of location wrappers in finish_id_expression.

Here we are parsing the decltype expression via cp_parser_decltype_expr which
can lead to calling various fold_* and c-family routines.  They use
non_lvalue_loc, but that won't create a NON_LVALUE_EXPR wrapper around a location
wrapper.

So before the location wrappers addition cp_parser_decltype_expr would return
NON_LVALUE_EXPR <c>.  Now it returns VIEW_CONVERT_EXPR<float *>(c), but the
STRIP_ANY_LOCATION_WRAPPER immediately following it strips the location wrapper,
and suddenly we don't know whether we have an lvalue anymore.  And that's sad
because then decltype produces the wrong type, causing nonsense errors.

	* fold-const.c (maybe_lvalue_p): Handle VIEW_CONVERT_EXPR.

	* g++.dg/cpp0x/decltype73.C: New test.

From-SVN: r279077

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 582ffe0..0994815 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2019-12-07  Marek Polacek  <polacek@redhat.com>
+
+       PR c++/91678 - wrong error with decltype and location wrapper.
+       * fold-const.c (maybe_lvalue_p): Handle VIEW_CONVERT_EXPR.
+
 2019-12-07  Eric Botcazou  <ebotcazou@adacore.com>
 
        PR middle-end/90840

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index c5bd45a..8e9e299 100644 (file)
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -2598,6 +2598,7 @@ maybe_lvalue_p (const_tree x)
   case TARGET_EXPR:
   case COND_EXPR:
   case BIND_EXPR:
+  case VIEW_CONVERT_EXPR:
     break;
 
   default:

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 460cff0..2d14412 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2019-12-07  Marek Polacek  <polacek@redhat.com>
+
+       PR c++/91678 - wrong error with decltype and location wrapper.
+       * g++.dg/cpp0x/decltype73.C: New test.
+
 2019-12-07  Jakub Jelinek  <jakub@redhat.com>
 
        PR c++/92831

diff --git a/gcc/testsuite/g++.dg/cpp0x/decltype73.C b/gcc/testsuite/g++.dg/cpp0x/decltype73.C
new file mode 100644 (file)
index 0000000..cbe94a8
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/decltype73.C
@@ -0,0 +1,4 @@
+// PR c++/91678 - wrong error with decltype and location wrapper.
+// { dg-do compile { target c++11 } }
+
+float* test(float* c) { return (decltype(c + 0))(float*)c; }