switch on error preserves error return trace

[Techatrix]

Zig Version

0.12.0-dev.2139+e025ad7b4

Steps to Reproduce and Observed Behavior

Run the following code with zig run file.zig:

pub fn main() !void {
 try foo();
 return error.FailTest;
}

fn failure() error{ Fatal, NonFatal }!void {
 return error.NonFatal;
}

fn foo() error{Fatal}!void {
 return failure() catch |err| switch (err) {
 error.Fatal => return error.Fatal,
 error.NonFatal => return,
 };
}

This will yield the following error return trace:

error: FailTest
/run/media/techatrix/UserFiles/zls/sample.zig:7:5: 0x1025af8 in failure (sample)
 return error.NonFatal;
 ^
/run/media/techatrix/UserFiles/zls/sample.zig:3:5: 0x10234a6 in main (sample)
 return error.FailTest;

---

I have reduced this example from usage of std.zig.Ast.parse:

pub fn main() !void {
 const std = @import("std");
 var tree = try std.zig.Ast.parse(std.heap.page_allocator, "const foo = ", .zig);
 defer tree.deinit(std.heap.page_allocator);

 return error.FailTest;
}

The equivalent of the foo function in the reduced example would be expectTopLevelDeclRecoverable.

zig/lib/std/zig/Parse.zig

Lines 670 to 678 in c724cc6

	fn expectTopLevelDeclRecoverable(p: *Parse) error{OutOfMemory}!Node.Index {
	return p.expectTopLevelDecl() catch |err| switch (err) {
	error.OutOfMemory => return error.OutOfMemory,
	error.ParseError => {
	p.findNextContainerMember();
	return null_node;
	},
	};
	}

Expected Behavior

The error return trace should not include the failure function because the NonFatal error is being ignored in the foo function.

error: FailTest
/run/media/techatrix/UserFiles/zls/sample.zig:11:5: 0x21e2f6 in main (sample)
 return error.FailTest;

This is also what Zig 0.11.0 would produce.

I suspect that this has been caused by #18173.