Proposed clarification of spec for int/float/complex promotion

Author: JelleZijlstra

conformance/results/mypy/specialtypes_promotions.toml

@@ -1,6 +1,7 @@
 conformant = "Pass"
 output = """
-specialtypes_promotions.py:13: error: "float" has no attribute "numerator"  [attr-defined]
+specialtypes_promotions.py:15: error: "float" has no attribute "numerator"  [attr-defined]
+specialtypes_promotions.py:27: error: Incompatible return value type (got "complex", expected "float")  [return-value]
 """
 conformance_automated = "Pass"
 errors_diff = """

conformance/results/mypy/version.toml

@@ -1,2 +1,2 @@
 version = "mypy 1.10.0"
-test_duration = 1.4
+test_duration = 1.2

conformance/results/pyre/specialtypes_promotions.toml

@@ -3,8 +3,9 @@ notes = """
 Does not reject use of attribute that is compatible only with float.
 """
 output = """
+specialtypes_promotions.py:27:8 Incompatible return type [7]: Expected `float` but got `complex`.
 """
 conformance_automated = "Fail"
 errors_diff = """
-Line 13: Expected 1 errors
+Line 15: Expected 1 errors
 """

conformance/results/pyre/version.toml

@@ -1,2 +1,2 @@
 version = "pyre 0.9.21"
-test_duration = 3.4
+test_duration = 1.7

conformance/results/pyright/specialtypes_promotions.toml

@@ -1,7 +1,9 @@
 conformant = "Pass"
 output = """
-specialtypes_promotions.py:13:7 - error: Cannot access attribute "numerator" for class "float"
+specialtypes_promotions.py:15:7 - error: Cannot access attribute "numerator" for class "float"
   Attribute "numerator" is unknown (reportAttributeAccessIssue)
+specialtypes_promotions.py:27:16 - error: Expression of type "complex" is incompatible with return type "float"
+  "complex" is incompatible with "float" (reportReturnType)
 """
 conformance_automated = "Pass"
 errors_diff = """

conformance/results/pyright/version.toml

@@ -1,2 +1,2 @@
 version = "pyright 1.1.364"
-test_duration = 1.4
+test_duration = 1.3

conformance/results/pytype/specialtypes_promotions.toml

@@ -1,6 +1,7 @@
 conformant = "Pass"
 output = """
-File "specialtypes_promotions.py", line 13, in func1: No attribute 'numerator' on float [attribute-error]
+File "specialtypes_promotions.py", line 15, in func1: No attribute 'numerator' on float [attribute-error]
+File "specialtypes_promotions.py", line 27, in func2: bad return type [bad-return-type]
 """
 conformance_automated = "Pass"
 errors_diff = """

conformance/results/pytype/version.toml

@@ -1,2 +1,2 @@
 version = "pytype 2024.04.11"
-test_duration = 30.1
+test_duration = 27.6

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'>1.4sec</div>
+<div class='tc-time'>1.2sec</div>
 </th>
 <th class='tc-header'><div class='tc-name'>pyright 1.1.364</div>
-<div class='tc-time'>1.4sec</div>
+<div class='tc-time'>1.3sec</div>
 </th>
 <th class='tc-header'><div class='tc-name'>pyre 0.9.21</div>
-<div class='tc-time'>3.4sec</div>
+<div class='tc-time'>1.7sec</div>
 </th>
 <th class='tc-header'><div class='tc-name'>pytype 2024.04.11</div>
-<div class='tc-time'>30.1sec</div>
+<div class='tc-time'>27.6sec</div>
 </th>
 </tr>
 <tr><th class="column" colspan="5">

conformance/tests/specialtypes_promotions.py

@@ -2,6 +2,8 @@
 Tests "type promotions" for float and complex when they appear in annotations.
 """
 
+from typing import assert_type
+
 # Specification: https://typing.readthedocs.io/en/latest/spec/special-types.html#special-cases-for-float-and-complex
 
 v1: float = 1
@@ -10,7 +12,20 @@
 
 
 def func1(f: float):
-    f.numerator  # E
+    f.numerator  # E: attribute exists on int but not float
+
+    if isinstance(f, float):
+        assert_type(f, float)
+    else:
+        assert_type(f, int)
+
 
-    if not isinstance(f, float):
-        f.numerator  # OK
+def func2(x: int) -> float:
+    if x == 0:
+        return 1
+    elif x == 1:
+        return 1j  # E
+    elif x > 10:
+        return x
+    else:
+        return 1.0