[D] Fix crash when debug expression enabled.

While casting works as expected with expression debugging turned off,
this seems to be an indication that the D language parser function is
doing something wrong in the building of the expression.

Without changing the grammar, using UNOP_CAST_TYPE is the right thing to
do here, as the TypeExp handler has already wrapped the type around a
pair of OP_TYPE opcodes.

gdb/ChangeLog:

	* d-exp.y (CastExpression): Emit UNOP_CAST_TYPE.

gdb/testsuite/ChangeLog:

	* gdb.dlang/debug-expr.exp: New file.

2 files changed, 44 insertions, 0 deletions

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index d12072b..8a03282 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2017-01-08  Iain Buclaw  <ibuclaw@gdcproject.org>
+
+	* gdb.dlang/debug-expr.exp: New file.
+
 2016-12-23  Luis Machado  <lgustavo@codesourcery.com>
 
 	Fix test names for the following files:
diff --git a/gdb/testsuite/gdb.dlang/debug-expr.exp b/gdb/testsuite/gdb.dlang/debug-expr.exp
new file mode 100644
index 0000000..d62dcc6
--- /dev/null
+++ b/gdb/testsuite/gdb.dlang/debug-expr.exp
@@ -0,0 +1,40 @@
+# Copyright 2017 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test "set debug expr 1" on d expressions.
+
+if { [skip_d_tests] } { return -1 }
+
+gdb_start
+gdb_test_no_output "set language d"
+gdb_test_no_output "set debug expression 1"
+
+# Test whether the expression debug machinery accepts the expression.
+
+proc test_debug_expr { cmd output } {
+    global gdb_prompt
+
+    gdb_test_multiple $cmd "" {
+	-re ".*Invalid expression.*\r\n$gdb_prompt $" {
+	    fail $cmd
+	}
+	-re ".*\[\r\n\]$output\r\n$gdb_prompt $" {
+	    pass $cmd
+	}
+    }
+}
+
+# This caused gdb to segfault.
+test_debug_expr "print *(int*)(0)" "Cannot access memory at address 0x0"