@let: bug re-using previously array-typed location as scalar.

* awkgram.y (let_var_list): We must generate the Op_clear_var
instruction even for variables which have initializers.
Otherwise the initialization will bomb if the initializer is
scalar, and the location we are re-using held an array previously.

* interpret.h (r_interpret): Do not use the get_lhs function,
which has complex semantics that depend on the existing type,
and may initialize the value, as well as blow up for an array.
We work directly with var->var_value. If var already has the
new variable type, we have nothing to do. We now unref the
prior value only if the prior type is Node_var, because prior
array values and such don't support unref.

* test/let1.awk: Extension of test case which reproduced this
problem, plus additional test cases for coverage of the duplicated
code in the Yacc grammar.

1 files changed, 13 insertions, 8 deletions

diff --git a/interpret.h b/interpret.h
index 0dc261d6..f239406f 100644
--- a/interpret.h
+++ b/interpret.h
@@ -753,16 +753,21 @@ mod:
 			 * initialized frame locations.
 			 */
 			NODE *var = pc->memory;
-			lhs = get_lhs(var, false);
 
-			/*
-			 * If it's already clear, nothing to do
-			 */
-			if (*lhs != Nnull_string) {
-				unref(*lhs);
-				*lhs = dupnode(Nnull_string);
+			if (var->type != Node_var_new) {
+				NODETYPE prevtype = var->type;
+				var->type = Node_var_new;
+				var->flags &= MALLOC;
+
+				/*
+				 * If it's already clear, nothing to do
+				 */
+				if (var->var_value != Nnull_string) {
+					if (prevtype == Node_var)
+						unref(var->var_value);
+					var->var_value = dupnode(Nnull_string);
+				}
 			}
-			var->type = Node_var_new;
 		}
 			break;