Simplify the check: we can name primitive literals just as well, it should not be common

Author: sterliakov

mypy/checker.py

@@ -75,7 +75,6 @@
     CallExpr,
     ClassDef,
     ComparisonExpr,
-    ComplexExpr,
     Context,
     ContinueStmt,
     Decorator,
@@ -5572,19 +5571,8 @@ def visit_match_stmt(self, s: MatchStmt) -> None:
     def _make_named_statement_for_match(self, s: MatchStmt) -> Expression:
         """Construct a fake NameExpr for inference if a match clause is complex."""
         subject = s.subject
-        expressions_to_preserve = (
+        if isinstance(subject, (NameExpr, AssignmentExpr)):
             # Already named - we should infer type of it as given
-            NameExpr,
-            AssignmentExpr,
-            # Primitive literals - their type is known, no need to name them
-            IntExpr,
-            StrExpr,
-            BytesExpr,
-            FloatExpr,
-            ComplexExpr,
-            EllipsisExpr,
-        )
-        if isinstance(subject, expressions_to_preserve):
             return subject
         elif s.subject_dummy is not None:
             return s.subject_dummy

test-data/unit/check-python310.test

@@ -2613,6 +2613,27 @@ match A().foo:
     case other:
         other  # E: Statement is unreachable
 
+[case testMatchLiteral]
+# flags: --warn-unreachable
+
+def int_literal() -> None:
+    match 12:
+        case 1 as s:
+            reveal_type(s)  # N: Revealed type is "Literal[1]"
+        case int(i):
+            reveal_type(i)  # N: Revealed type is "Literal[12]?"
+        case other:
+            other  # E: Statement is unreachable
+
+def str_literal() -> None:
+    match 'foo':
+        case 'a' as s:
+            reveal_type(s)  # N: Revealed type is "Literal['a']"
+        case str(i):
+            reveal_type(i)  # N: Revealed type is "Literal['foo']?"
+        case other:
+            other  # E: Statement is unreachable
+
 [case testMatchOperations]
 # flags: --warn-unreachable