Incorrect type shown in language server's hover over suffixed expressions

[snobee]

When hovering over the values in the file below the types shown are incorrect for everything in main, except for test2 and Stdin.line!

app [main] {
    pf: platform "https://github.com/roc-lang/basic-cli/releases/download/0.15.0/SlwdbJ-3GR7uBWQo6zlmYWNYOxnvo8r6YABXD-45UOw.tar.br",
}

import pf.Stdin

main =
    test1 = "testing"
    test2 = Stdin.line!
    test3 = 1_2_3
    Task.ok {}

Expected behavior

The types of the values when hovering should be
test1, "testing": Str
test2: Str
Stdin.line!: Task {} [...]
test3, 1_2_3: Num *
Task.ok: {} -> Task {} *
{}: {}

Actual behaviour

test2: Str
Stdin.line!: Task {} [...]
everything else in main: Str -> Task {} [...]

I believe the problem is in roc_can::traverse::TypeAtPositionVisitor and roc_can::traverse::find_closest_type_at which finds the type of the closure generated by the canonicalization of ! instead of the proper definition.

The same thing happens with ? suffix as well.

[lukewilliamboswell]

My guess is that we are messing up the regions with desugaring of the suffixes, and that is somehow related.

[snobee]

My guess is that we are messing up the regions with desugaring of the suffixes, and that is somehow related.

That could be it. I checked the output ast from this example by generating a .snap file from can/tests

snapshot

Defs {
    tags: [
        Index(2147483648),
    ],
    regions: [
        @0-85,
    ],
    space_before: [
        Slice(start = 0, length = 0),
    ],
    space_after: [
        Slice(start = 0, length = 1),
    ],
    spaces: [
        Newline,
    ],
    type_defs: [],
    value_defs: [
        Body(
            @0-4 Identifier {
                ident: "main",
            },
            @11-85 Defs(
                Defs {
                    tags: [
                        Index(2147483648),
                    ],
                    regions: [
                        @19-28,
                    ],
                    space_before: [
                        Slice(start = 0, length = 0),
                    ],
                    space_after: [
                        Slice(start = 0, length = 0),
                    ],
                    spaces: [],
                    type_defs: [],
                    value_defs: [
                        Body(
                            @11-16 Identifier {
                                ident: "test1",
                            },
                            @19-28 Str(
                                PlainLine(
                                    "testing",
                                ),
                            ),
                        ),
                    ],
                },
                @11-85 Apply(
                    @11-85 Var {
                        module_name: "Task",
                        ident: "await",
                    },
                    [
                        @41-52 Var {
                            module_name: "Stdin",
                            ident: "line",
                        },
                        @11-85 Closure(
                            [
                                @33-38 Identifier {
                                    ident: "test2",
                                },
                            ],
                            @41-52 Defs(
                                Defs {
                                    tags: [
                                        Index(2147483648),
                                    ],
                                    regions: [
                                        @65-70,
                                    ],
                                    space_before: [
                                        Slice(start = 0, length = 1),
                                    ],
                                    space_after: [
                                        Slice(start = 1, length = 0),
                                    ],
                                    spaces: [
                                        Newline,
                                    ],
                                    type_defs: [],
                                    value_defs: [
                                        Body(
                                            @57-62 Identifier {
                                                ident: "test3",
                                            },
                                            @65-70 Num(
                                                "1_2_3",
                                            ),
                                        ),
                                    ],
                                },
                                @75-85 Apply(
                                    @75-82 Var {
                                        module_name: "Task",
                                        ident: "ok",
                                    },
                                    [
                                        @83-85 Record(
                                            [],
                                        ),
                                    ],
                                    Space,
                                ),
                            ),
                        ),
                    ],
                    BangSuffix,
                ),
            ),
        ),
    ],
}

I'm not very familiar with this but it looks like the Defs node with test3 and Task.ok has the region @41-52 which explains hovering on test3 at 60 doesn't reach it. Is it supposed to be @57-85 instead? That would contain all the regions of the nodes inside it.

Also, is there a better way to print out parts of the ast than creating a snapshot file? I couldn't find anything

[lukewilliamboswell]

I think making a test is the easiest way. You could also add a test for the parser if you want the AST before it's been desugared which may help see the regions easier see crates/compiler/test_syntax/tests/snapshots for those.