feat: improve parser error msgs

Author: boriel

src/api/errmsg.py

@@ -333,4 +333,18 @@ def syntax_error_mandatory_param_after_optional(lineno: int, param1: str, param2
     error(lineno, f"Can't declare mandatory param '{param2}' after optional param '{param1}'")
 
 
+# ----------------------------------------
+# FOR without NEXT
+# ----------------------------------------
+def syntax_error_for_without_next(lineno: int):
+    error(lineno, "FOR without NEXT")
+
+
+# ----------------------------------------
+# FOR without NEXT
+# ----------------------------------------
+def syntax_error_loop_not_closed(lineno: int, loop_type: str):
+    error(lineno, f"{loop_type} loop not closed")
+
+
 # endregion

src/zxbc/zxbparser.py

@@ -3401,6 +3401,13 @@ def p_error(p):
         error(p.lineno, msg)
         return
 
+    # Try to give some hints
+    if gl.LOOPS:  # some loop(s) are not closed
+        loop_info = gl.LOOPS[-1]
+        if loop_info.type == LoopType.FOR:
+            src.api.errmsg.syntax_error_for_without_next(loop_info.lineno)
+        else:
+            src.api.errmsg.syntax_error_loop_not_closed(loop_info.lineno, loop_info.type)
     # If there were previous errors, stop here
     # since this end of file is due to previous errors
     if gl.has_errors:

tests/functional/test_errmsg.txt

@@ -206,6 +206,14 @@ 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
 
+# Test parsing error improvements
+>>> process_file('zx48k/for_err.bas')
+for_err.bas:3: error: FOR without NEXT
+>>> process_file('zx48k/while_err.bas')
+while_err.bas:3: error: WHILE loop not closed
+>>> process_file('zx48k/do_err.bas')
+do_err.bas:3: error: DO loop not closed
+
 # Unreachable code detection
 # Should not emit warning for these case:
 >>> process_file('zx48k/warn_unreach0.bas')

tests/functional/zx48k/do_err.bas

@@ -0,0 +1,5 @@
+DIM i, c as Ubyte
+
+DO
+  LET c = c * 2
+

tests/functional/zx48k/for_err.bas

@@ -0,0 +1,5 @@
+DIM i, c as Ubyte
+
+FOR i = 1 TO 5
+  LET c = c * 2
+

tests/functional/zx48k/while_err.bas

@@ -0,0 +1,5 @@
+DIM i, c as Ubyte
+
+WHILE i = 1
+  LET c = c * 2
+