t-strings: Add more syntax tests (python#68)

Author: AA-Turner

Lib/test/test_grammar.py

@@ -1506,6 +1506,8 @@ def check(test):
         check('[None (3, 4)]')
         check('[True (3, 4)]')
         check('[... (3, 4)]')
+        check('[t"{x}" (3, 4)]')
+        check('[t"x={x}" (3, 4)]')
 
         msg=r'is not subscriptable; perhaps you missed a comma\?'
         check('[{1, 2} [i, j]]')
@@ -1528,6 +1530,8 @@ def check(test):
         check('[f"x={x}" [i, j]]')
         check('["abc" [i, j]]')
         check('[b"abc" [i, j]]')
+        check('[t"{x}" [i, j]]')
+        check('[t"x={x}" [i, j]]')
 
         msg=r'indices must be integers or slices, not tuple;'
         check('[[1, 2] [3, 4]]')
@@ -1548,6 +1552,8 @@ def check(test):
         check('[[1, 2] [f"{x}"]]')
         check('[[1, 2] [f"x={x}"]]')
         check('[[1, 2] ["abc"]]')
+        check('[[1, 2] [t"{x}"]]')
+        check('[[1, 2] [t"x={x}"]]')
         msg=r'indices must be integers or slices, not'
         check('[[1, 2] [b"abc"]]')
         check('[[1, 2] [12.3]]')

Lib/test/test_syntax.py

@@ -1735,6 +1735,14 @@
 Traceback (most recent call last):
 SyntaxError: cannot assign to f-string expression here. Maybe you meant '==' instead of '='?
 
+>>> t'{x}' = 42
+Traceback (most recent call last):
+SyntaxError: cannot assign to t-string expression here. Maybe you meant '==' instead of '='?
+
+>>> t'{x}-{y}' = 42
+Traceback (most recent call last):
+SyntaxError: cannot assign to t-string expression here. Maybe you meant '==' instead of '='?
+
 >>> (x, y, z=3, d, e)
 Traceback (most recent call last):
 SyntaxError: invalid syntax. Maybe you meant '==' or ':=' instead of '='?

Lib/test/test_tstring.py

@@ -367,26 +367,39 @@ def test_ast_structure(self):
         self.assertIsInstance(tree.body[0].value.values[0], ast.Constant)
         self.assertIsInstance(tree.body[0].value.values[1], ast.Interpolation)
 
-    def test_error_conditions(self):
-        # Test syntax errors
-        with self.assertRaisesRegex(SyntaxError, "'{' was never closed"):
-            eval("t'{")
-
-        with self.assertRaisesRegex(SyntaxError, "t-string: expecting '}'"):
-            eval("t'{a'")
-
-        with self.assertRaisesRegex(SyntaxError, "t-string: single '}' is not allowed"):
-            eval("t'}'")
-
+    def test_syntax_errors(self):
+        for case, err in (
+            ("t'", "unterminated t-string literal"),
+            ("t'''", "unterminated triple-quoted t-string literal"),
+            ("t''''", "unterminated triple-quoted t-string literal"),
+            ("t'{", "'{' was never closed"),
+            ("t'{'", "t-string: expecting '}'"),
+            ("t'{a'", "t-string: expecting '}'"),
+            ("t'}'", "t-string: single '}' is not allowed"),
+            ("t'{}'", "t-string: valid expression required before '}'"),
+            ("t'{=x}'", "t-string: valid expression required before '='"),
+            ("t'{!x}'", "t-string: valid expression required before '!'"),
+            ("t'{:x}'", "t-string: valid expression required before ':'"),
+            ("t'{x;y}'", "t-string: expecting '=', or '!', or ':', or '}'"),
+            ("t'{x=y}'", "t-string: expecting '!', or ':', or '}'"),
+            ("t'{x!s!}'", "t-string: expecting ':' or '}'"),
+            ("t'{x!s:'", "t-string: expecting '}', or format specs"),
+            ("t'{x!}'", "t-string: missing conversion character"),
+            ("t'{x=!}'", "t-string: missing conversion character"),
+            ("t'{x!z}'", "t-string: invalid conversion character 'z': "
+                         "expected 's', 'r', or 'a'"),
+            ("t'{lambda:1}'", "t-string: lambda expressions are not allowed "
+                              "without parentheses"),
+            ("t'{x:{;}}'", "t-string: expecting a valid expression after '{'"),
+        ):
+            with self.subTest(case), self.assertRaisesRegex(SyntaxError, err):
+                eval(case)
+
+    def test_runtime_errors(self):
         # Test missing variables
         with self.assertRaises(NameError):
             eval("t'Hello, {name}'")
 
-        # Test invalid conversion
-        num = 1
-        with self.assertRaises(SyntaxError):
-            eval("t'{num!z}'")
-
     def test_literal_concatenation(self):
         # Test concatenation of t-string literals
         t = t"Hello, " t"world"