Issue #27985: Implement PEP 526 -- Syntax for Variable Annotations.

Patch by Ivan Levkivskyi.

2 files changed, 33 insertions, 2 deletions

diff --git a/Lib/lib2to3/Grammar.txt b/Lib/lib2to3/Grammar.txt
index c954669..abe1268 100644
--- a/Lib/lib2to3/Grammar.txt
+++ b/Lib/lib2to3/Grammar.txt
@@ -54,12 +54,13 @@ stmt: simple_stmt | compound_stmt
 simple_stmt: small_stmt (';' small_stmt)* [';'] NEWLINE
 small_stmt: (expr_stmt | print_stmt  | del_stmt | pass_stmt | flow_stmt |
              import_stmt | global_stmt | exec_stmt | assert_stmt)
-expr_stmt: testlist_star_expr (augassign (yield_expr|testlist) |
+expr_stmt: testlist_star_expr (annassign | augassign (yield_expr|testlist) |
                      ('=' (yield_expr|testlist_star_expr))*)
+annassign: ':' test ['=' test]
 testlist_star_expr: (test|star_expr) (',' (test|star_expr))* [',']
 augassign: ('+=' | '-=' | '*=' | '@=' | '/=' | '%=' | '&=' | '|=' | '^=' |
             '<<=' | '>>=' | '**=' | '//=')
-# For normal assignments, additional restrictions enforced by the interpreter
+# For normal and annotated assignments, additional restrictions enforced by the interpreter
 print_stmt: 'print' ( [ test (',' test)* [','] ] |
                       '>>' test [ (',' test)+ [','] ] )
 del_stmt: 'del' exprlist
diff --git a/Lib/lib2to3/tests/test_parser.py b/Lib/lib2to3/tests/test_parser.py
index 9adb031..b378163 100644
--- a/Lib/lib2to3/tests/test_parser.py
+++ b/Lib/lib2to3/tests/test_parser.py
@@ -237,6 +237,36 @@ class TestFunctionAnnotations(GrammarTest):
         self.validate(s)
 
 
+# Adapted from Python 3's Lib/test/test_grammar.py:GrammarTests.test_var_annot
+class TestFunctionAnnotations(GrammarTest):
+    def test_1(self):
+        self.validate("var1: int = 5")
+
+    def test_2(self):
+        self.validate("var2: [int, str]")
+
+    def test_3(self):
+        self.validate("def f():\n"
+                      "    st: str = 'Hello'\n"
+                      "    a.b: int = (1, 2)\n"
+                      "    return st\n")
+
+    def test_4(self):
+        self.validate("def fbad():\n"
+                      "    x: int\n"
+                      "    print(x)\n")
+
+    def test_5(self):
+        self.validate("class C:\n"
+                      "    x: int\n"
+                      "    s: str = 'attr'\n"
+                      "    z = 2\n"
+                      "    def __init__(self, x):\n"
+                      "        self.x: int = x\n")
+
+    def test_6(self):
+        self.validate("lst: List[int] = []")
+
 class TestExcept(GrammarTest):
     def test_new(self):
         s = """