Merge branch 'delete-non-indexed-expression'

internal/vm/checker/checker.go

@@ -612,8 +612,11 @@ func (c *checker) VisitAfter(node ast.Node) ast.Node {
 		return n
 
 	case *ast.DelStmt:
-		n.N.(*ast.IndexedExpr).Lhs.(*ast.IdTerm).Lvalue = true
-		return n
+		if ix, ok := n.N.(*ast.IndexedExpr); ok {
+			ix.Lhs.(*ast.IdTerm).Lvalue = true
+			return n
+		}
+		c.errors.Add(n.Pos(), fmt.Sprintf("Cannot delete this.\n\tTry deleting from a dimensioned metric with this as an index."))
 
 	}
 

internal/vm/checker/checker_test.go

@@ -183,6 +183,12 @@ next
 @x {}
 }`,
 		[]string{"use decorator in decorator:2:1-2: Decorator `@x' is not completely defined yet.", "\tTry removing @x from here.", "use decorator in decorator:2:1-2: No symbols found in decorator `@x'.", "\tTry adding a `next' statement inside the `{}' block."}},
+
+	{"delete incorrect object",
+		`/(.*)/ {
+del $0
+}`,
+		[]string{"delete incorrect object:3:7: Cannot delete this.", "\tTry deleting from a dimensioned metric with this as an index."}},
 }
 
 func TestCheckInvalidPrograms(t *testing.T) {