Improve exception formatting

Resolves   #794.

coconut/compiler/compiler.py

@@ -1218,10 +1218,10 @@ def make_err(self, errtype, message, original, loc=0, ln=None, extra=None, refor
             kwargs["extra"] = extra
         return errtype(message, snippet, loc_in_snip, ln, endpoint=endpt_in_snip, filename=self.filename, **kwargs)
 
-    def make_syntax_err(self, err, original):
+    def make_syntax_err(self, err, original, after_parsing=False):
         """Make a CoconutSyntaxError from a CoconutDeferredSyntaxError."""
         msg, loc = err.args
-        return self.make_err(CoconutSyntaxError, msg, original, loc)
+        return self.make_err(CoconutSyntaxError, msg, original, loc, endpoint=not after_parsing)
 
     def make_parse_err(self, err, msg=None, include_ln=True, **kwargs):
         """Make a CoconutParseError from a ParseBaseException."""
@@ -1328,7 +1328,7 @@ def parse(
                     filename=filename,
                     incremental_cache_filename=incremental_cache_filename,
                 ))
-            pre_procd = None
+            pre_procd = parsed = None
             try:
                 with logger.gather_parsing_stats():
                     try:
@@ -1339,7 +1339,7 @@ def parse(
                         raise self.make_parse_err(err)
                     except CoconutDeferredSyntaxError as err:
                         internal_assert(pre_procd is not None, "invalid deferred syntax error in pre-processing", err)
-                        raise self.make_syntax_err(err, pre_procd)
+                        raise self.make_syntax_err(err, pre_procd, after_parsing=parsed is not None)
                     # RuntimeError, not RecursionError, for Python < 3.5
                     except RuntimeError as err:
                         raise CoconutException(

coconut/exceptions.py

@@ -180,11 +180,14 @@ def message(self, message, source, point, ln, extra=None, endpoint=None, filenam
                     point_ind = clip(point_ind, 0, len(lines[0]))
                     endpoint_ind = clip(endpoint_ind, 0, len(lines[-1]))
 
+                    max_line_len = max(len(line) for line in lines)
+
                     message += "\n" + " " * (taberrfmt + point_ind)
                     if point_ind >= len(lines[0]):
-                        message += "|\n"
+                        message += "|"
                     else:
-                        message += "/" + "~" * (len(lines[0]) - point_ind - 1) + "\n"
+                        message += "/" + "~" * (len(lines[0]) - point_ind - 1)
+                    message += "~" * (max_line_len - len(lines[0])) + "\n"
                     for line in lines:
                         message += "\n" + " " * taberrfmt + line
                     message += (

coconut/root.py

@@ -26,7 +26,7 @@
 VERSION = "3.0.3"
 VERSION_NAME = None
 # False for release, int >= 1 for develop
-DEVELOP = 16
+DEVELOP = 17
 ALPHA = False  # for pre releases rather than post releases
 
 assert DEVELOP is False or DEVELOP >= 1, "DEVELOP must be False or an int >= 1"

coconut/tests/src/cocotest/agnostic/primary_2.coco

@@ -1,11 +1,10 @@
 import collections
 import collections.abc
 import weakref
+import sys
 
-if TYPE_CHECKING:
+if TYPE_CHECKING or sys.version_info >= (3, 5):
     from typing import Any, Iterable
-else:
-    Any = Iterable = None
 from importlib import reload  # NOQA
 
 from .util import assert_raises, typed_eq

coconut/tests/src/extras.coco

@@ -277,6 +277,21 @@ def gam_eps_rate(bitarr) = (
     else:
         assert False
 
+    try:
+        parse("""
+def f(x=1, y) = x, y
+
+class A
+
+def g(x) = x
+        """.strip())
+    except CoconutSyntaxError as err:
+        err_str = str(err)
+        assert "non-default arguments must come first" in err_str, err_str
+        assert "class A" not in err_str, err_str
+    else:
+        assert False
+
     assert parse("def f(x):\n ${var}", "xonsh") == "def f(x):\n    ${var}\n"
     assert "data ABC" not in parse("data ABC:\n ${var}", "xonsh")