Feb 10, 2023 · Feb 9, 2023 · Feb 9, 2023 · Feb 9, 2023
diff --git a/mypy/partially_defined.py b/mypy/partially_defined.py
        self.tracker.end_branch_statement()

    def visit_match_stmt(self, o: MatchStmt) -> None:
        self.tracker.start_branch_statement()
        o.subject.accept(self)
        self.tracker.start_branch_statement()
        for i in range(len(o.patterns)):
            pattern = o.patterns[i]
            pattern.accept(self)
diff --git a/test-data/unit/check-python310.test b/test-data/unit/check-python310.test

 [typing fixtures/typing-medium.pyi]

 [case testUsedBeforeDefMatchWalrus]
 # flags: --enable-error-code used-before-def
 import typing

 def f0(x: int) -> None:
    a = y  # E: Cannot determine type of "y"  # E: Name "y" is used before definition
    match y := x:
        case 1:
            b = y
        case 2:
            c = y
    d = y


 [case testTypeAliasWithNewUnionSyntaxAndNoneLeftOperand]
 from typing import overload
 class C:
Original file line number	Diff line number	Diff line change
Expand Up		@@ -396,8 +396,8 @@ def visit_if_stmt(self, o: IfStmt) -> None:
		self.tracker.end_branch_statement()

		def visit_match_stmt(self, o: MatchStmt) -> None:
		self.tracker.start_branch_statement()
		o.subject.accept(self)
		self.tracker.start_branch_statement()
		for i in range(len(o.patterns)):
		pattern = o.patterns[i]
		pattern.accept(self)
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1813,6 +1813,20 @@ def f1(x: int) -> int:

		[typing fixtures/typing-medium.pyi]

		[case testUsedBeforeDefMatchWalrus]
		# flags: --enable-error-code used-before-def
		import typing

		def f0(x: int) -> None:
		a = y # E: Cannot determine type of "y" # E: Name "y" is used before definition
		match y := x:
		case 1:
		b = y
		case 2:
		c = y
		d = y


		[case testTypeAliasWithNewUnionSyntaxAndNoneLeftOperand]
		from typing import overload
		class C:
Expand Down