Improve else handling with custom equality (#20692)

hauntsaninja · web-flow · commit 070917381cb8 · 2026-01-29T22:38:39.000-08:00
diff --git a/mypy/checker.py b/mypy/checker.py
@@ -6752,8 +6752,7 @@ def narrow_type_by_identity_equality(
                         if_map, else_map = conditional_types_to_typemaps(
                             operands[i], *conditional_types(expr_type, [target])
                         )
-                        if else_map:
-                            all_else_maps.append(else_map)
+                        all_else_maps.append(else_map)
                 continue
 
             # If our operand with custom __eq__ is a union, where only some members of the union
diff --git a/test-data/unit/check-narrowing.test b/test-data/unit/check-narrowing.test
@@ -880,7 +880,7 @@ def f1(x: Literal[1, 2, None], y: Custom):
         reveal_type(x)   # N: Revealed type is "Literal[1]"
         reveal_type(y)   # N: Revealed type is "__main__.Custom"
     else:
-        reveal_type(x)   # N: Revealed type is "Literal[2] | None"
+        reveal_type(x)   # N: Revealed type is "Literal[1] | Literal[2] | None"
         reveal_type(y)   # N: Revealed type is "__main__.Custom"
 
 class Default: pass

Original file line number	Diff line number	Diff line change
`@@ -6752,8 +6752,7 @@ def narrow_type_by_identity_equality(`
`6752`	`6752`	`if_map, else_map = conditional_types_to_typemaps(`
`6753`	`6753`	`operands[i], *conditional_types(expr_type, [target])`
`6754`	`6754`	`)`
`6755`		`- if else_map:`
`6756`		`- all_else_maps.append(else_map)`
	`6755`	`+ all_else_maps.append(else_map)`
`6757`	`6756`	`continue`
`6758`	`6757`
`6759`	`6758`	`# If our operand with custom __eq__ is a union, where only some members of the union`