Defer Ada character literal resolution

In Ada, an enumeration type can use a character literal as one of the
enumerators.  The Ada expression parser handles the appropriate
conversion.

It turns out, though, that this conversion was handled incorrectly.
For an expression like TYPE'(EXP), the conversion would be done for
any such literal appearing in EXP -- but only the outermost such
expression should really be affected.

This patch defers the conversion until the resolution phase, fixing
the bug.

gdb/ada-lang.c

@@ -10114,6 +10114,66 @@ ada_resolvable::replace (operation_up &&owner,
   return std::move (owner);
 }
 
+/* Convert the character literal whose ASCII value would be VAL to the
+   appropriate value of type TYPE, if there is a translation.
+   Otherwise return VAL.  Hence, in an enumeration type ('A', 'B'),
+   the literal 'A' (VAL == 65), returns 0.  */
+
+static LONGEST
+convert_char_literal (struct type *type, LONGEST val)
+{
+  char name[7];
+  int f;
+
+  if (type == NULL)
+    return val;
+  type = check_typedef (type);
+  if (type->code () != TYPE_CODE_ENUM)
+    return val;
+
+  if ((val >= 'a' && val <= 'z') || (val >= '0' && val <= '9'))
+    xsnprintf (name, sizeof (name), "Q%c", (int) val);
+  else
+    xsnprintf (name, sizeof (name), "QU%02x", (int) val);
+  size_t len = strlen (name);
+  for (f = 0; f < type->num_fields (); f += 1)
+    {
+      /* Check the suffix because an enum constant in a package will
+	 have a name like "pkg__QUxx".  This is safe enough because we
+	 already have the correct type, and because mangling means
+	 there can't be clashes.  */
+      const char *ename = TYPE_FIELD_NAME (type, f);
+      size_t elen = strlen (ename);
+
+      if (elen >= len && strcmp (name, ename + elen - len) == 0)
+	return TYPE_FIELD_ENUMVAL (type, f);
+    }
+  return val;
+}
+
+/* See ada-exp.h.  */
+
+operation_up
+ada_char_operation::replace (operation_up &&owner,
+			     struct expression *exp,
+			     bool deprocedure_p,
+			     bool parse_completion,
+			     innermost_block_tracker *tracker,
+			     struct type *context_type)
+{
+  operation_up result = std::move (owner);
+
+  if (context_type != nullptr && context_type->code () == TYPE_CODE_ENUM)
+    {
+      gdb_assert (result.get () == this);
+      std::get<0> (m_storage) = context_type;
+      std::get<1> (m_storage)
+	= convert_char_literal (context_type, std::get<1> (m_storage));
+    }
+
+  return make_operation<ada_wrapped_operation> (std::move (result));
+}
+
 value *
 ada_wrapped_operation::evaluate (struct type *expect_type,
 				 struct expression *exp,