add rule for discarding of values

src/rules/_list.zig

@@ -1,6 +1,7 @@
 pub const @"anyerror" = @import("anyerror.zig");
 pub const carriage_return = @import("carriage_return.zig");
 pub const comment_start = @import("comment_start.zig");
+pub const discard_value = @import("discard_value.zig");
 pub const empty_line_at_file_end = @import("empty_line_at_file_end.zig");
 pub const if_for_while_braces = @import("if_for_while_braces.zig");
 pub const imports = @import("imports.zig");

src/rules/discard_value.zig

@@ -0,0 +1,27 @@
+const std = @import("std");
+
+const main = @import("main");
+
+pub fn check(ctx: main.Context) void {
+	const ast = ctx.ast orelse return;
+
+	for (0..ast.nodes.len) |nodeIndex| {
+		const node: std.zig.Ast.Node.Index = @enumFromInt(nodeIndex);
+		if (ast.nodeTag(node) != .assign) continue;
+
+		const data = ast.nodeData(node).node_and_node;
+
+		const name = data.@"0".toOptional().unwrap() orelse continue;
+		var expression = data.@"1".toOptional().unwrap() orelse continue;
+
+		while (ast.nodeTag(expression) == .address_of) {
+			expression = ast.nodeData(expression).node;
+		}
+
+		if (ast.nodeTag(name) != .identifier) continue;
+		if (ast.nodeTag(expression) != .identifier) continue;
+		if (!std.mem.eql(u8, ast.getNodeSource(name), "_")) continue;
+
+		ctx.printError("Do not discard variables, for parameters discard the parameter directly", ast.tokenStart(ast.nodeMainToken(node)));
+	}
+}