Fix unary + in Ada

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

@@ -1,3 +1,7 @@
+2021-03-15  Tom Tromey  <tromey@adacore.com>
+
+	* ada-exp.y (simple_exp): Always push a result for unary '+'.
+
 2021-03-15  Tom Tromey  <tromey@adacore.com>
 
 	* ada-lang.c (ada_unop_ind_operation::evaluate): Call

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));
 			}
 	;
 

gdb/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2021-03-15  Tom Tromey  <tromey@adacore.com>
+
+	* gdb.ada/fixed_points.exp: Add tests of unary + and -.
+
 2021-03-15  Tom Tromey  <tromey@adacore.com>
 
 	* gdb.ada/varsize_limit.exp: Add new test.

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