gh-118082: Improve import without names syntax error message (#118083)

Author: sobolevn

Grammar/python.gram

@@ -1299,10 +1299,14 @@ invalid_group:
 invalid_import:
     | a='import' ','.dotted_name+ 'from' dotted_name {
         RAISE_SYNTAX_ERROR_STARTING_FROM(a, "Did you mean to use 'from ... import ...' instead?") }
+    | 'import' token=NEWLINE { 
+        RAISE_SYNTAX_ERROR_STARTING_FROM(token, "Expected one or more names after 'import'") }
 
 invalid_import_from_targets:
     | import_from_as_names ',' NEWLINE {
         RAISE_SYNTAX_ERROR("trailing comma not allowed without surrounding parentheses") }
+    | token=NEWLINE { 
+        RAISE_SYNTAX_ERROR_STARTING_FROM(token, "Expected one or more names after 'import'") }
 
 invalid_compound_stmt:
     | a='elif' named_expression ':' { RAISE_SYNTAX_ERROR_STARTING_FROM(a, "'elif' must match an if-statement here") }

Lib/test/test_syntax.py

@@ -1699,6 +1699,18 @@
 Traceback (most recent call last):
 SyntaxError: invalid syntax
 
+>>> from i import
+Traceback (most recent call last):
+SyntaxError: Expected one or more names after 'import'
+
+>>> from .. import
+Traceback (most recent call last):
+SyntaxError: Expected one or more names after 'import'
+
+>>> import
+Traceback (most recent call last):
+SyntaxError: Expected one or more names after 'import'
+
 >>> (): int
 Traceback (most recent call last):
 SyntaxError: only single target (not tuple) can be annotated

Misc/NEWS.d/next/Core and Builtins/2024-04-19-11-59-57.gh-issue-118082._FLuOT.rst

@@ -0,0 +1,3 @@
+Improve :exc:`SyntaxError` message for imports without names, like in
+``from x import`` and ``import`` cases. It now points
+out to users that :keyword:`import` expects at least one name after it.