Conformance suite: rewrite directives_version_platform.py to not assume that type checkers will ignore all errors in unreachable code (#2202)

Co-authored-by: Carl Meyer <carl@oddbird.net>

Author: AlexWaygood

conformance/results/mypy/directives_version_platform.toml

@@ -4,10 +4,11 @@ Does not understand three-element form of sys.version checks.
 Does not understand os.name checks.
 """
 output = """
-directives_version_platform.py:19: error: Incompatible types in assignment (expression has type "str", variable has type "int")  [assignment]
-directives_version_platform.py:27: error: Incompatible types in assignment (expression has type "str", variable has type "int")  [assignment]
-directives_version_platform.py:40: error: Incompatible types in assignment (expression has type "str", variable has type "int")  [assignment]
-directives_version_platform.py:45: error: Incompatible types in assignment (expression has type "str", variable has type "int")  [assignment]
+directives_version_platform.py:26: error: Expression is of type "int | str", not "int"  [assert-type]
+directives_version_platform.py:33: error: Name "val3" is not defined  [name-defined]
+directives_version_platform.py:42: error: Expression is of type "int | str", not "int"  [assert-type]
+directives_version_platform.py:50: error: Name "val6" is not defined  [name-defined]
+directives_version_platform.py:59: error: Name "val9" is not defined  [name-defined]
 """
 conformance_automated = "Pass"
 errors_diff = """

conformance/results/pyrefly/directives_version_platform.toml

@@ -3,6 +3,11 @@ conformance_automated = "Pass"
 errors_diff = """
 """
 output = """
-ERROR directives_version_platform.py:40:17-19: `Literal['']` is not assignable to `int` [bad-assignment]
-ERROR directives_version_platform.py:45:17-19: `Literal['']` is not assignable to `int` [bad-assignment]
+ERROR directives_version_platform.py:33:19-23: Could not find name `val3` [unknown-name]
+ERROR directives_version_platform.py:50:19-23: Could not find name `val6` [unknown-name]
+ERROR directives_version_platform.py:59:19-23: Could not find name `val9` [unknown-name]
+ERROR directives_version_platform.py:66:19-24: `val10` may be uninitialized [unbound-name]
+ERROR directives_version_platform.py:67:22-27: `val11` may be uninitialized [unbound-name]
+ERROR directives_version_platform.py:74:22-27: `val12` may be uninitialized [unbound-name]
+ERROR directives_version_platform.py:75:19-24: `val13` may be uninitialized [unbound-name]
 """

conformance/results/pyright/directives_version_platform.toml

@@ -1,5 +1,10 @@
 conformant = "Pass"
 output = """
+directives_version_platform.py:33:19 - error: "val3" is not defined (reportUndefinedVariable)
+directives_version_platform.py:50:19 - error: "val6" is not defined (reportUndefinedVariable)
+directives_version_platform.py:59:19 - error: "val9" is not defined (reportUndefinedVariable)
+directives_version_platform.py:66:19 - error: "val10" is not defined (reportUndefinedVariable)
+directives_version_platform.py:75:19 - error: "val13" is not defined (reportUndefinedVariable)
 """
 conformance_automated = "Pass"
 errors_diff = """

conformance/results/zuban/directives_version_platform.toml

@@ -2,8 +2,9 @@ conformance_automated = "Pass"
 errors_diff = """
 """
 output = """
-directives_version_platform.py:19: error: Incompatible types in assignment (expression has type "str", variable has type "int")  [assignment]
-directives_version_platform.py:27: error: Incompatible types in assignment (expression has type "str", variable has type "int")  [assignment]
-directives_version_platform.py:40: error: Incompatible types in assignment (expression has type "str", variable has type "int")  [assignment]
-directives_version_platform.py:45: error: Incompatible types in assignment (expression has type "str", variable has type "int")  [assignment]
+directives_version_platform.py:26: error: Expression is of type "int | str", not "int"  [misc]
+directives_version_platform.py:33: error: Name "val3" is not defined  [name-defined]
+directives_version_platform.py:42: error: Expression is of type "int | str", not "int"  [misc]
+directives_version_platform.py:50: error: Name "val6" is not defined  [name-defined]
+directives_version_platform.py:59: error: Name "val9" is not defined  [name-defined]
 """

conformance/tests/directives_version_platform.py

@@ -6,40 +6,70 @@
 
 import os
 import sys
+from typing import assert_type
 
+def test(a: int, b: str):
+    val1: int | str
+    if sys.version_info >= (3, 8):
+        val1 = a
+    else:
+        val1 = b
 
-if sys.version_info >= (3, 8):
-    pass
-else:
-    val1: int = ""  # Should not generate an error
+    assert_type(val1, int)
 
-if sys.version_info >= (3, 8, 0):
-    pass
-else:
-    val2: int = ""  # E?: May not generate an error (support for three-element sys.version is optional)
+    val2: int | str
+    if sys.version_info >= (3, 8, 0):
+        val2 = a
+    else:
+        val2 = b
 
-if sys.version_info < (3, 8):
-    val3: int = ""  # Should not generate an error
+    assert_type(val2, int)  # E?: May not generate an error (support for three-element sys.version is optional)
 
-if sys.version_info < (3, 100, 0):
-    pass
-else:
-    val3: int = ""  # E?: May not generate an error (support for three-element sys.version is optional)
+    if sys.version_info < (3, 8):
+        val3 = ""
+    else:
+        val4 = ""
 
+    this_raises = val3  # E: `val3` is undefined
+    does_not_raise = val4  # should not error
 
-if sys.platform == "bogus_platform":
-    val5: int = ""  # Should not generate an error
+    val5: int | str
+    if sys.version_info < (3, 100, 0):
+        val5 = a
+    else:
+        val5 = b
 
-if sys.platform != "bogus_platform":
-    pass
-else:
-    val6: int = ""  # Should not generate an error
+    assert_type(val5, int)  # E?: May not generate an error (support for three-element sys.version is optional)
 
 
-if os.name == "bogus_os":
-    val7: int = ""  # E?: May not generate an error (support for os.name is optional)
+    if sys.platform == "bogus_platform":
+        val6 = ""
+    else:
+        val7 = ""
 
-if os.name != "bogus_platform":
-    pass
-else:
-    val8: int = ""  # E?: May not generate an error (support for os.name is optional)
+    this_raises = val6  # E: `val6` is undefined
+    does_not_raise = val7  # should not error
+
+    if sys.platform != "bogus_platform":
+        val8 = ""
+    else:
+        val9 = ""
+
+    does_not_raise = val8  # should not error
+    this_raises = val9  # E: `val9` is undefined
+
+    if os.name == "bogus_os":
+        val10 = ""
+    else:
+        val11 = ""
+
+    this_raises = val10  # E?: `val10` is undefined, but support for `os.name` is optional
+    does_not_raise = val11  # E? should not error if `os.name` control flow is supported, but might be flagged as possibly undefined otherwise
+
+    if os.name != "bogus_os":
+        val12 = ""
+    else:
+        val13 = ""
+
+    does_not_raise = val12  # E?: should not error if `os.name` control flow is supported, but might be flagged as possibly undefined otherwise
+    this_raises = val13  # E?: `val13` is undefined, but support for `os.name` is optional