gdb: address review comments of previous series

I forgot to include fixes for review comments I got before pushing the
previous commits (or I pushed the wrong commits).  This one fixes it.

 - Return {} instead of false in get_discrete_low_bound and
   get_discrete_high_bound.
 - Compute high bound after confirming low bound is valid in
   get_discrete_bounds.

gdb/ChangeLog:

	* gdbtypes.c (get_discrete_low_bound, get_discrete_high_bound):
	Return {} instead of false.
	(get_discrete_bounds): Compute high bound only if low bound is
	valid.

Change-Id: I5f9a66b3672adfac9441068c899ab113ab2c331a

2 files changed, 15 insertions, 6 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0b08eaf..dd13414 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2020-12-09  Simon Marchi  <simon.marchi@polymtl.ca>
+
+	* gdbtypes.c (get_discrete_low_bound, get_discrete_high_bound):
+	Return {} instead of false.
+	(get_discrete_bounds): Compute high bound only if low bound is
+	valid.
+
 2020-12-09  Simon Marchi  <simon.marchi@efficios.com>
 
 	PR 26875, PR 26901
diff --git a/gdb/gdbtypes.c b/gdb/gdbtypes.c
index 9cd7992..6c1cd08 100644
--- a/gdb/gdbtypes.c
+++ b/gdb/gdbtypes.c
@@ -1081,7 +1081,7 @@ get_discrete_low_bound (struct type *type)
 
     case TYPE_CODE_INT:
       if (TYPE_LENGTH (type) > sizeof (LONGEST))	/* Too big */
-	return false;
+	return {};
 
       if (!TYPE_UNSIGNED (type))
 	return -(1 << (TYPE_LENGTH (type) * TARGET_CHAR_BIT - 1));
@@ -1091,7 +1091,7 @@ get_discrete_low_bound (struct type *type)
       return 0;
 
     default:
-      return false;
+      return {};
     }
 }
 
@@ -1148,7 +1148,7 @@ get_discrete_high_bound (struct type *type)
 
     case TYPE_CODE_INT:
       if (TYPE_LENGTH (type) > sizeof (LONGEST))	/* Too big */
-	return false;
+	return {};
 
       if (!TYPE_UNSIGNED (type))
 	{
@@ -1167,7 +1167,7 @@ get_discrete_high_bound (struct type *type)
       }
 
     default:
-      return false;
+      return {};
     }
 }
 
@@ -1177,9 +1177,11 @@ bool
 get_discrete_bounds (struct type *type, LONGEST *lowp, LONGEST *highp)
 {
   gdb::optional<LONGEST> low = get_discrete_low_bound (type);
-  gdb::optional<LONGEST> high = get_discrete_high_bound (type);
+  if (!low.has_value ())
+    return false;
 
-  if (!low.has_value () || !high.has_value ())
+  gdb::optional<LONGEST> high = get_discrete_high_bound (type);
+  if (!high.has_value ())
     return false;
 
   *lowp = *low;