[pushed] Avoid assertion failure due to complex type change

[Tom Tromey]

Tankut Baris Aktemur pointed out that the recent series to change how
complex types are handled introduced a regression.

This assert in init_complex_type was firing:

  gdb_assert (TYPE_CODE (target_type) == TYPE_CODE_INT
	      || TYPE_CODE (target_type) == TYPE_CODE_FLT);

The problem was that f-lang.c could call init_complex_type with a type
whose code was TYPE_CODE_ERROR.

It seemed best to me to fix this in f-lang.c, rather than to change
init_complex_type to accept error types.

Tested on x86-64 Fedora 30.  I'm checking this in.

gdb/ChangeLog
2020-04-02  Tom Tromey  <tromey@adacore.com>

	* f-lang.c (build_fortran_types): Use arch_type to initialize
	builtin_complex_s32 in the TYPE_CODE_ERROR case.
---
 gdb/ChangeLog | 5 +++++
 gdb/f-lang.c  | 9 +++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/gdb/f-lang.c b/gdb/f-lang.c
index 2ce4ad43610..6b7a5fb7dba 100644
--- a/gdb/f-lang.c
+++ b/gdb/f-lang.c
@@ -744,8 +744,13 @@ build_fortran_types (struct gdbarch *gdbarch)
     = init_complex_type ("complex*8", builtin_f_type->builtin_real);
   builtin_f_type->builtin_complex_s16
     = init_complex_type ("complex*16", builtin_f_type->builtin_real_s8);
-  builtin_f_type->builtin_complex_s32
-    = init_complex_type ("complex*32", builtin_f_type->builtin_real_s16);
+
+  if (TYPE_CODE (builtin_f_type->builtin_real_s16) == TYPE_CODE_ERROR)
+    builtin_f_type->builtin_complex_s32
+      = arch_type (gdbarch, TYPE_CODE_ERROR, 256, "complex*32");
+  else
+    builtin_f_type->builtin_complex_s32
+      = init_complex_type ("complex*32", builtin_f_type->builtin_real_s16);
 
   return builtin_f_type;
 }
-- 
2.21.1