[pushed] Fix unary + in Ada

[Tom Tromey <tromey@adacore.com>]

My previous Ada patches introduced a bug that I found after checkin.
I had incorrectly implemented unary +.  There was a test for the
overloaded case, but no test for the ordinary case.

This patch adds the tests and fixes the bug.
Tested on x86-64 Fedora 32.

gdb/ChangeLog
2021-03-15  Tom Tromey  <tromey@adacore.com>

	* ada-exp.y (simple_exp): Always push a result for unary '+'.

gdb/testsuite/ChangeLog
2021-03-15  Tom Tromey  <tromey@adacore.com>

	* gdb.ada/fixed_points.exp: Add tests of unary + and -.
---
 gdb/ChangeLog                          | 4 ++++
 gdb/ada-exp.y                          | 8 +++++---
 gdb/testsuite/ChangeLog                | 4 ++++
 gdb/testsuite/gdb.ada/fixed_points.exp | 5 +++++
 4 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/gdb/ada-exp.y b/gdb/ada-exp.y
index e8ffb8e1040..146b1acbe14 100644
--- a/gdb/ada-exp.y
+++ b/gdb/ada-exp.y
@@ -589,12 +589,14 @@ simple_exp :	'+' simple_exp    %prec UNARY
 			  operation_up arg = ada_pop ();
 			  operation_up empty;
 
-			  /* We only need to handle the overloading
-			     case here, not anything else.  */
+			  /* If an overloaded operator was found, use
+			     it.  Otherwise, unary + has no effect and
+			     the argument can be pushed instead.  */
 			  operation_up call = maybe_overload (UNOP_PLUS, arg,
 							      empty);
 			  if (call != nullptr)
-			    pstate->push (std::move (call));
+			    arg = std::move (call);
+			  pstate->push (std::move (arg));
 			}
 	;
 
diff --git a/gdb/testsuite/gdb.ada/fixed_points.exp b/gdb/testsuite/gdb.ada/fixed_points.exp
index 7267c3181ed..69565e77490 100644
--- a/gdb/testsuite/gdb.ada/fixed_points.exp
+++ b/gdb/testsuite/gdb.ada/fixed_points.exp
@@ -76,6 +76,11 @@ foreach_with_prefix scenario {all minimal} {
     gdb_test "print fp2_var - 0" \
 	" = -0.01"
 
+    gdb_test "print + fp2_var" \
+	" = -0.01"
+    gdb_test "print - fp2_var" \
+	" = 0.01"
+
     set fp4 "= 2e-07"
     gdb_test "print fp4_var" $fp4
     gdb_test "print fp4_var * 1" $fp4
-- 
2.26.2