scanContainer

fn scanContainer(
    astgen: *AstGen,
    namespace: *Scope.Namespace,
    members: []const Ast.Node.Index,
    container_kind: enum { @"struct", @"union", @"enum", @"opaque" },
) !ScanContainerResult {
    const gpa = astgen.gpa;
    const tree = astgen.tree;

    var any_invalid_declarations = false;

    // This type forms a linked list of source tokens declaring the same name.
    const NameEntry = struct {
        tok: Ast.TokenIndex,
        /// Using a linked list here simplifies memory management, and is acceptable since
        ///ewntries are only allocated in error situations. The entries are allocated into the
        /// AstGen arena.
        next: ?*@This(),
    };

    // The maps below are allocated into this BFA to avoid using the GPA for small namespaces.
    var bfa_buf: [512]u8 = undefined;
    var bfa_state: std.heap.BufferFirstAllocator = .init(&bfa_buf, astgen.gpa);
    const bfa = bfa_state.allocator();

    var names: std.array_hash_map.Auto(Zir.NullTerminatedString, NameEntry) = .empty;
    var test_names: std.array_hash_map.Auto(Zir.NullTerminatedString, NameEntry) = .empty;
    var decltest_names: std.array_hash_map.Auto(Zir.NullTerminatedString, NameEntry) = .empty;
    defer {
        names.deinit(bfa);
        test_names.deinit(bfa);
        decltest_names.deinit(bfa);
    }

    var any_duplicates = false;
    var decl_count: u32 = 0;
    var any_field_aligns = false;
    var any_field_values = false;
    var any_comptime_fields = false;
    var has_underscore_field = false;
    for (members) |member_node| {
        const Kind = enum { decl, field };
        const kind: Kind, const name_token = switch (tree.nodeTag(member_node)) {
            .container_field_init,
            .container_field_align,
            .container_field,
            => blk: {
                var full = tree.fullContainerField(member_node).?;
                switch (container_kind) {
                    .@"struct", .@"opaque" => {},
                    .@"union", .@"enum" => full.convertToNonTupleLike(astgen.tree),
                }
                if (full.ast.align_expr != .none) any_field_aligns = true;
                if (full.ast.value_expr != .none) any_field_values = true;
                if (full.comptime_token != null) any_comptime_fields = true;
                if (mem.eql(u8, tree.tokenSlice(full.ast.main_token), "_")) has_underscore_field = true;
                if (full.ast.tuple_like) continue;
                break :blk .{ .field, full.ast.main_token };
            },

            .global_var_decl,
            .local_var_decl,
            .simple_var_decl,
            .aligned_var_decl,
            => blk: {
                decl_count += 1;
                break :blk .{ .decl, tree.nodeMainToken(member_node) + 1 };
            },

            .fn_proto_simple,
            .fn_proto_multi,
            .fn_proto_one,
            .fn_proto,
            .fn_decl,
            => blk: {
                decl_count += 1;
                const ident = tree.nodeMainToken(member_node) + 1;
                if (tree.tokenTag(ident) != .identifier) {
                    try astgen.appendErrorNode(member_node, "missing function name", .{});
                    any_invalid_declarations = true;
                    continue;
                }
                break :blk .{ .decl, ident };
            },

            .@"comptime" => {
                decl_count += 1;
                continue;
            },

            .test_decl => {
                decl_count += 1;
                // We don't want shadowing detection here, and test names work a bit differently, so
                // we must do the redeclaration detection ourselves.
                const test_name_token = tree.nodeMainToken(member_node) + 1;
                const new_ent: NameEntry = .{
                    .tok = test_name_token,
                    .next = null,
                };
                switch (tree.tokenTag(test_name_token)) {
                    else => {}, // unnamed test
                    .string_literal => {
                        const name = try astgen.strLitAsString(test_name_token);
                        const gop = try test_names.getOrPut(bfa, name.index);
                        if (gop.found_existing) {
                            var e = gop.value_ptr;
                            while (e.next) |n| e = n;
                            e.next = try astgen.arena.create(NameEntry);
                            e.next.?.* = new_ent;
                            any_duplicates = true;
                        } else {
                            gop.value_ptr.* = new_ent;
                        }
                    },
                    .identifier => {
                        const name = try astgen.identAsString(test_name_token);
                        const gop = try decltest_names.getOrPut(bfa, name);
                        if (gop.found_existing) {
                            var e = gop.value_ptr;
                            while (e.next) |n| e = n;
                            e.next = try astgen.arena.create(NameEntry);
                            e.next.?.* = new_ent;
                            any_duplicates = true;
                        } else {
                            gop.value_ptr.* = new_ent;
                        }
                    },
                }
                continue;
            },

            else => unreachable,
        };

        const name_str_index = try astgen.identAsString(name_token);

        if (kind == .decl) {
            // Put the name straight into `decls`, even if there are compile errors.
            // This avoids incorrect "undeclared identifier" errors later on.
            try namespace.decls.put(gpa, name_str_index, member_node);
        }

        {
            const gop = try names.getOrPut(bfa, name_str_index);
            const new_ent: NameEntry = .{
                .tok = name_token,
                .next = null,
            };
            if (gop.found_existing) {
                var e = gop.value_ptr;
                while (e.next) |n| e = n;
                e.next = try astgen.arena.create(NameEntry);
                e.next.?.* = new_ent;
                any_duplicates = true;
                continue;
            } else {
                gop.value_ptr.* = new_ent;
            }
        }

        // For fields, we only needed the duplicate check! Decls have some more checks to do, though.
        switch (kind) {
            .decl => {},
            .field => continue,
        }

        const token_bytes = astgen.tree.tokenSlice(name_token);
        if (token_bytes[0] != '@' and isPrimitive(token_bytes)) {
            try astgen.appendErrorTokNotes(name_token, "name shadows primitive '{s}'", .{
                token_bytes,
            }, &.{
                try astgen.errNoteTok(name_token, "consider using @\"{s}\" to disambiguate", .{
                    token_bytes,
                }),
            });
            any_invalid_declarations = true;
            continue;
        }

        find_scope: switch (namespace.parent.unwrap()) {
            .local_val => |local_val| {
                if (local_val.name == name_str_index) {
                    try astgen.appendErrorTokNotes(name_token, "declaration '{s}' shadows {s} from outer scope", .{
                        token_bytes, @tagName(local_val.id_cat),
                    }, &.{
                        try astgen.errNoteTok(
                            local_val.token_src,
                            "previous declaration here",
                            .{},
                        ),
                    });
                    any_invalid_declarations = true;
                    break :find_scope;
                }
                continue :find_scope local_val.parent.unwrap();
            },
            .local_ptr => |local_ptr| {
                if (local_ptr.name == name_str_index) {
                    try astgen.appendErrorTokNotes(name_token, "declaration '{s}' shadows {s} from outer scope", .{
                        token_bytes, @tagName(local_ptr.id_cat),
                    }, &.{
                        try astgen.errNoteTok(
                            local_ptr.token_src,
                            "previous declaration here",
                            .{},
                        ),
                    });
                    any_invalid_declarations = true;
                    break :find_scope;
                }
                continue :find_scope local_ptr.parent.unwrap();
            },
            .namespace => |ns| continue :find_scope ns.parent.unwrap(),
            .gen_zir => |gen_zir| continue :find_scope gen_zir.parent.unwrap(),
            .defer_normal, .defer_error => |defer_scope| continue :find_scope defer_scope.parent.unwrap(),
            .top => break :find_scope,
        }
    }

    if (!any_duplicates) {
        if (any_invalid_declarations) return error.AnalysisFail;
        return .{
            .decls_len = decl_count,
            .fields_len = @intCast(members.len - decl_count),
            .any_field_aligns = any_field_aligns,
            .any_field_values = any_field_values,
            .any_comptime_fields = any_comptime_fields,
            .has_underscore_field = has_underscore_field,
        };
    }

    for (names.keys(), names.values()) |name, first| {
        if (first.next == null) continue;
        var notes: std.ArrayList(u32) = .empty;
        var prev: NameEntry = first;
        while (prev.next) |cur| : (prev = cur.*) {
            try notes.append(astgen.arena, try astgen.errNoteTok(cur.tok, "duplicate name here", .{}));
        }
        try notes.append(astgen.arena, try astgen.errNoteNode(namespace.node, "{s} declared here", .{@tagName(container_kind)}));
        const name_duped = try astgen.arena.dupe(u8, mem.span(astgen.nullTerminatedString(name)));
        try astgen.appendErrorTokNotes(first.tok, "duplicate {s} member name '{s}'", .{ @tagName(container_kind), name_duped }, notes.items);
        any_invalid_declarations = true;
    }

    for (test_names.keys(), test_names.values()) |name, first| {
        if (first.next == null) continue;
        var notes: std.ArrayList(u32) = .empty;
        var prev: NameEntry = first;
        while (prev.next) |cur| : (prev = cur.*) {
            try notes.append(astgen.arena, try astgen.errNoteTok(cur.tok, "duplicate test here", .{}));
        }
        try notes.append(astgen.arena, try astgen.errNoteNode(namespace.node, "{s} declared here", .{@tagName(container_kind)}));
        const name_duped = try astgen.arena.dupe(u8, mem.span(astgen.nullTerminatedString(name)));
        try astgen.appendErrorTokNotes(first.tok, "duplicate test name '{s}'", .{name_duped}, notes.items);
        any_invalid_declarations = true;
    }

    for (decltest_names.keys(), decltest_names.values()) |name, first| {
        if (first.next == null) continue;
        var notes: std.ArrayList(u32) = .empty;
        var prev: NameEntry = first;
        while (prev.next) |cur| : (prev = cur.*) {
            try notes.append(astgen.arena, try astgen.errNoteTok(cur.tok, "duplicate decltest here", .{}));
        }
        try notes.append(astgen.arena, try astgen.errNoteNode(namespace.node, "{s} declared here", .{@tagName(container_kind)}));
        const name_duped = try astgen.arena.dupe(u8, mem.span(astgen.nullTerminatedString(name)));
        try astgen.appendErrorTokNotes(first.tok, "duplicate decltest '{s}'", .{name_duped}, notes.items);
        any_invalid_declarations = true;
    }

    assert(any_invalid_declarations);
    return error.AnalysisFail;
}