[errors] Two fixes for location info in word eval

This is issue #2129

- Reset self.loc_for_expr on every line
  - the expression location is supposed to refine the line location
- Pass location info in Stringify(), so we don't need to use the
  fallback location

core/state.py

@@ -1353,6 +1353,7 @@ def SetTokenForLine(self, tok):
         #traceback.print_stack()
         #return
 
+        self.loc_for_expr = loc.Missing  # reset it on every line
         self.token_for_line = tok
 
     def SetLocationForExpr(self, blame_loc):

frontend/location.py

@@ -13,6 +13,7 @@
     loc,
     loc_t,
     loc_e,
+    loc_str,
     command,
     command_e,
     command_t,
@@ -110,7 +111,7 @@ def TokenFor(loc_):
                 return None
 
         else:
-            raise AssertionError()
+            raise AssertionError(loc_str(loc_.tag()))
 
     raise AssertionError()
 

osh/word_eval.py

@@ -227,7 +227,7 @@ def _ValueToPartValue(val, quoted, part_loc):
         # value_e.List is also here - we use val_ops.Stringify()s err message
         elif case(value_e.Null, value_e.Bool, value_e.Int, value_e.Float,
                   value_e.Eggex, value_e.List):
-            s = val_ops.Stringify(val, loc.Missing, 'Word eval ')
+            s = val_ops.Stringify(val, loc.WordPart(part_loc), 'Word eval ')
             return Piece(s, quoted, not quoted)
 
         else:

test/ysh-runtime-errors.sh

@@ -1131,6 +1131,23 @@ test-int-overflow() {
   _ysh-expr-error "= int('$neg')"
 }
 
+test-bug-2129() {
+  # bug in interactive only
+
+  _assert-sh-status 3 $YSH 'Should fail under YSH' \
+    -i -c '
+proc p (...args) {
+  echo $args
+}
+
+p 1 2 3
+
+echo $[{}]
+
+p 1 2 3
+'
+}
+
 soil-run-py() {
   run-test-funcs
 }