fix broken tests, elaborate on test file format in the readme

Author: wyattscarpenter

test-data/unit/README.md

@@ -31,17 +31,23 @@ with text "abc..."
 - note a space after `E:` and `flags:`
 - `# E:12` adds column number to the expected error
 - use `\` to escape the `#` character and indicate that the rest of the line is part of
-the error message (note that there is no support for using `\\` to escape a backslash itself)
+  the error message (note that there is no support for using `\\` to escape a backslash itself
+  in this context; also, in all other contexts, such as line-continuation, the backslash is treated
+  as it normally would be in a python source file)
 - repeating `# E: ` several times in one line indicates multiple expected errors in one line
 - `W: ...` and `N: ...` works exactly like `E: ...`, but report a warning and a note respectively
 - lines that don't contain the above should cause no type check errors
+- lines that begin with `--` are test-file-format comments, and will not appear in the texted python
+  source code
+- some test files are run in a special way by the test runner; this is typically documented in
+  test-file-format comments at the top of the test file
 - optional `[builtins fixtures/...]` tells the type checker to use
 `builtins` stubs from the indicated file (see Fixtures section below)
 - optional `[out]` is an alternative to the `# E: ` notation: it indicates that
-any text after it contains the expected type checking error messages.
-Usually, `# E: ` is preferred because it makes it easier to associate the
-errors with the code generating them at a glance, and to change the code of
-the test without having to change line numbers in `[out]`
+  any text after it contains the expected type checking error messages.
+  Usually, `# E: ` is preferred because it makes it easier to associate the
+  errors with the code generating them at a glance, and to change the code of
+  the test without having to change line numbers in `[out]`
 - an empty `[out]` section has no effect
 - to add tests for a feature that hasn't been implemented yet, append `-xfail`
   to the end of the test name

test-data/unit/check-classes.test

@@ -695,7 +695,7 @@ class A:
     def __replace__(self, x: Optional[str]) -> Self: pass
 
 class B(A):
-    def __replace__(self, x: str) -> Self: pass # E: \
+    def __replace__(self, x: str) -> Self: pass \
         # E: Argument 1 of "__replace__" is incompatible with supertype "A"; supertype defines the argument type as "Optional[str]"  [override] \
         # N: This violates the Liskov substitution principle \
         # N: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides

test-data/unit/check-deprecated.test

@@ -49,7 +49,8 @@ from typing_extensions import deprecated
 @deprecated("use f2 instead")
 def f() -> None: ...
 
-f  # E: function __main__.f is deprecated: use f2 instead  # type: ignore[deprecated]
+f # type: ignore[deprecated]
+f # E: function __main__.f is deprecated: use f2 instead
 f(1)  # E: function __main__.f is deprecated: use f2 instead \
       # E: Too many arguments for "f"
 f[1]  # E: function __main__.f is deprecated: use f2 instead \

test-data/unit/check-newsemanal.test

@@ -2684,7 +2684,7 @@ class C:
             ) -> str:
         return 0 # E: Incompatible return value type (got "int", expected "str")
 
-reveal_type(C.X) # E:  # N: Revealed type is "def () -> __main__.X"
+reveal_type(C.X)       # N: Revealed type is "def () -> __main__.X"
 reveal_type(C().str()) # N: Revealed type is "builtins.str"
 
 [case testNewAnalyzerNameNotDefinedYetInClassBody]

test-data/unit/check-type-aliases.test

@@ -551,12 +551,7 @@ def take_id(x: Id[int]) -> None:
 def id(x: Id[T]) -> T:
     return x
 
-# TODO: This doesn't work and maybe it should?
-# Indirection = AnInt[T]
-# y: Indirection[str]
-# reveal_type(y)  # E : Revealed type is "builtins.int"
-
-# But this does
+# Contrast with the TODO below
 Indirection2 = FlexibleAlias[T, AnInt[T]]
 z: Indirection2[str]
 reveal_type(z)  # N: Revealed type is "builtins.int"
@@ -567,6 +562,16 @@ reveal_type(w)  # N: Revealed type is "builtins.int"
 
 [builtins fixtures/dict.pyi]
 
+[case testFlexibleAlias1Todo-xfail]
+# TODO: This doesn't work and maybe it should?
+# Contrast with the example above that mentions this todo
+T = TypeVar('T')
+AnInt = FlexibleAlias[T, int]
+Indirection = AnInt[T]
+y: Indirection[str]
+reveal_type(y)  # N : Revealed type is "builtins.int"
+
+
 [case testFlexibleAlias2]
 # flags: --always-true=BOGUS
 from typing import TypeVar, Any

test-data/unit/check-typeddict.test

@@ -3652,7 +3652,7 @@ reveal_type(X)  # N: Revealed type is "builtins.dict[builtins.str, def () -> bui
 from typing_extensions import TypeAlias
 X: TypeAlias = {"int": int, "str": str}
 x: X
-reveal_type(x)  # N:  # N: Revealed type is "TypedDict({'int': builtins.int, 'str': builtins.str})"
+reveal_type(x)  # N: Revealed type is "TypedDict({'int': builtins.int, 'str': builtins.str})"
 [builtins fixtures/dict.pyi]
 [typing fixtures/typing-typeddict.pyi]