Method visit_or_pattern

mypy/checkpattern.py:154–202

(self, o: OrPattern)

        return PatternType(typ, rest_type, type_map)

    def visit_or_pattern(self, o: OrPattern) -> PatternType:
        current_type = self.type_context[-1]

        #
        # Check all the subpatterns
        #
        pattern_types = []
        for pattern in o.patterns:
            pattern_type = self.accept(pattern, current_type)
            pattern_types.append(pattern_type)
            if not is_uninhabited(pattern_type.type):
                current_type = pattern_type.rest_type

        #
        # Collect the final type
        #
        types = []
        for pattern_type in pattern_types:
            if not is_uninhabited(pattern_type.type):
                types.append(pattern_type.type)

        #
        # Check the capture types
        #
        capture_types: dict[Var, list[tuple[Expression, Type]]] = defaultdict(list)
        # Collect captures from the first subpattern
        for expr, typ in pattern_types[0].captures.items():
            node = get_var(expr)
            capture_types[node].append((expr, typ))

        # Check if other subpatterns capture the same names
        for i, pattern_type in enumerate(pattern_types[1:]):
            vars = {get_var(expr) for expr, _ in pattern_type.captures.items()}
            if capture_types.keys() != vars:
                self.msg.fail(message_registry.OR_PATTERN_ALTERNATIVE_NAMES, o.patterns[i])
            for expr, typ in pattern_type.captures.items():
                node = get_var(expr)
                capture_types[node].append((expr, typ))

        captures: dict[Expression, Type] = {}
        for capture_list in capture_types.values():
            typ = UninhabitedType()
            for _, other in capture_list:
                typ = make_simplified_union([typ, other])

            captures[capture_list[0][0]] = typ

        union_type = make_simplified_union(types)
        return PatternType(union_type, current_type, captures)

    def visit_value_pattern(self, o: ValuePattern) -> PatternType:
        current_type = self.type_context[-1]