Guard against unreachability

Author: JelleZijlstra

conformance/results/mypy/specialtypes_promotions.toml

@@ -1,8 +1,12 @@
-conformant = "Pass"
+conformant = "Partial"
+notes = """
+Does not narrow from float to int after isinstance() check
+"""
 output = """
 specialtypes_promotions.py:17: error: "float" has no attribute "numerator"  [attr-defined]
-specialtypes_promotions.py:29: error: Incompatible return value type (got "complex", expected "float")  [return-value]
+specialtypes_promotions.py:33: error: Incompatible return value type (got "complex", expected "float")  [return-value]
 """
-conformance_automated = "Pass"
+conformance_automated = "Fail"
 errors_diff = """
+Line 26: Expected 1 errors
 """

conformance/results/mypy/version.toml

@@ -1,2 +1,2 @@
 version = "mypy 1.10.0"
-test_duration = 6.2
+test_duration = 1.5

conformance/results/pyre/specialtypes_promotions.toml

@@ -1,11 +1,13 @@
 conformant = "Partial"
 notes = """
 Does not reject use of attribute that is compatible only with float.
+Does not narrow from float to int after isinstance() check
 """
 output = """
-specialtypes_promotions.py:29:8 Incompatible return type [7]: Expected `float` but got `complex`.
+specialtypes_promotions.py:33:8 Incompatible return type [7]: Expected `float` but got `complex`.
 """
 conformance_automated = "Fail"
 errors_diff = """
 Line 17: Expected 1 errors
+Line 26: Expected 1 errors
 """

conformance/results/pyre/version.toml

@@ -1,2 +1,2 @@
 version = "pyre 0.9.21"
-test_duration = 2.6
+test_duration = 2.9

conformance/results/pyright/specialtypes_promotions.toml

@@ -2,7 +2,9 @@ conformant = "Pass"
 output = """
 specialtypes_promotions.py:17:7 - error: Cannot access attribute "numerator" for class "float"
   Attribute "numerator" is unknown (reportAttributeAccessIssue)
-specialtypes_promotions.py:29:16 - error: Expression of type "complex" is incompatible with return type "float"
+specialtypes_promotions.py:26:16 - error: Expression of type "Literal['x']" is incompatible with return type "int"
+  "Literal['x']" is incompatible with "int" (reportReturnType)
+specialtypes_promotions.py:33:16 - error: Expression of type "complex" is incompatible with return type "float"
   "complex" is incompatible with "float" (reportReturnType)
 """
 conformance_automated = "Pass"

conformance/results/pyright/version.toml

@@ -1,2 +1,2 @@
 version = "pyright 1.1.364"
-test_duration = 1.8
+test_duration = 1.6

conformance/results/pytype/specialtypes_promotions.toml

@@ -1,8 +1,12 @@
-conformant = "Pass"
+conformant = "Partial"
+notes = """
+Does not narrow from float to int after isinstance() check
+"""
 output = """
 File "specialtypes_promotions.py", line 17, in func1: No attribute 'numerator' on float [attribute-error]
-File "specialtypes_promotions.py", line 29, in func2: bad return type [bad-return-type]
+File "specialtypes_promotions.py", line 33, in func2: bad return type [bad-return-type]
 """
-conformance_automated = "Pass"
+conformance_automated = "Fail"
 errors_diff = """
+Line 26: Expected 1 errors
 """

conformance/results/pytype/version.toml

@@ -1,2 +1,2 @@
 version = "pytype 2024.04.11"
-test_duration = 54.5
+test_duration = 49.8

conformance/results/results.html

@@ -159,16 +159,16 @@ <h3>Python Type System Conformance Test Results</h3>
         <div class="table_container"><table><tbody>
 <tr><th class="col1">&nbsp;</th>
 <th class='tc-header'><div class='tc-name'>mypy 1.10.0</div>
-<div class='tc-time'>6.2sec</div>
+<div class='tc-time'>1.5sec</div>
 </th>
 <th class='tc-header'><div class='tc-name'>pyright 1.1.364</div>
-<div class='tc-time'>1.8sec</div>
+<div class='tc-time'>1.6sec</div>
 </th>
 <th class='tc-header'><div class='tc-name'>pyre 0.9.21</div>
-<div class='tc-time'>2.6sec</div>
+<div class='tc-time'>2.9sec</div>
 </th>
 <th class='tc-header'><div class='tc-name'>pytype 2024.04.11</div>
-<div class='tc-time'>54.5sec</div>
+<div class='tc-time'>49.8sec</div>
 </th>
 </tr>
 <tr><th class="column" colspan="5">

conformance/tests/specialtypes_promotions.py

@@ -13,13 +13,17 @@
 v4 = 1
 
 
-def func1(f: float):
+def func1(f: float) -> int:
     f.numerator  # E: attribute exists on int but not float
 
     if isinstance(f, float):
         f.hex()  # OK (attribute exists on float but not int)
+        return 1
     else:
         assert_type(f, int)
+        # Make sure type checkers don't treat this branch as unreachable
+        # and skip checking it.
+        return "x"  # E
 
 
 def func2(x: int) -> float: