Stage struct fields used from sprites are still reported as unused

[aspizu]

Repro

tmp=$(mktemp -d /tmp/goboscript-stage-struct-used-sprite-XXXXXX)
printf 'costumes "blank.svg";\n\nstruct Point {\n    x,\n    y,\n}\n\nvar Point p = Point {\n    x: 1,\n    y: 2,\n};\n' > "$tmp/stage.gs"
printf 'costumes "blank.svg";\n\nonflag {\n    say p.x;\n}\n' > "$tmp/main.gs"
printf '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1"></svg>\n' > "$tmp/blank.svg"
cargo run --quiet -- build "$tmp"

Observed:

warning: unused struct Point
warning: unused struct field x (never read)
warning: unused struct field y (never read)

p.x is read by the sprite script, but the stage struct and x field are still reported unused.

Expected

References from sprite scripts to stage/global struct variables should mark the stage struct and accessed field as used. In this repro, Point and Point.x should not warn as unused.

[linear]

GS-279

[aspizu]

Additional repro: using a stage-defined struct type in a sprite-local variable also leaves the stage struct and field marked unused.

tmp=$(mktemp -d /tmp/goboscript-stage-struct-type-sprite-XXXXXX)
printf 'costumes "blank.svg";\n\nstruct Point {\n    x,\n}\n' > "$tmp/stage.gs"
printf 'costumes "blank.svg";\n\nvar Point p = Point { x: 1 };\n\nonflag {\n    say p.x;\n}\n' > "$tmp/main.gs"
printf '<svg xmlns="http://www.w3.org/2000/svg" width="1" height="1"></svg>\n' > "$tmp/blank.svg"
cargo run --quiet -- build "$tmp"

Observed warnings:

warning: unused struct Point
warning: unused struct field x (never read)