fix: fixes crash on bad array index

Author: boriel

src/zxbc/zxbparser.py

@@ -323,7 +323,10 @@ def make_array_access(id_, lineno, arglist):
     This is an RVALUE (Read the element)
     """
     for i, arg in enumerate(arglist):
-        arg.value = make_typecast(TYPE.by_name(src.api.constants.TYPE.to_string(gl.BOUND_TYPE)), arg.value, arg.lineno)
+        value = make_typecast(TYPE.by_name(src.api.constants.TYPE.to_string(gl.BOUND_TYPE)), arg.value, arg.lineno)
+        if value is None:  # semantic error?
+            return None  # return error
+        arg.value = value
 
     return symbols.ARRAYACCESS.make_node(id_, arglist, lineno, gl.FILENAME)
 

tests/functional/test_errmsg.txt

@@ -206,6 +206,9 @@ dim_str_error0.bas:3: error: Cannot initialize array of type string
 >>> process_file('zx48k/dim_str_error1.bas')
 dim_str_error1.bas:3: error: Cannot initialize array of type string
 
+>>> process_file('zx48k/sn_crash.bas')
+sn_crash.bas:4: error: Cannot convert string to a value. Use VAL() function
+
 # Test parsing error improvements
 >>> process_file('zx48k/for_err.bas')
 for_err.bas:3: error: FOR without NEXT

tests/functional/zx48k/sn_crash.bas

@@ -0,0 +1,4 @@
+DIM p(10) AS Ubyte
+DIM f as String
+
+LET p(f) = 0