feat: default struct field values

[SchoolyB]

Summary

Grayscale structs support default field values (STANDARD.md §3.2.3). The LSP symbol scanner does not currently handle the = expr suffix on struct fields.

Example

const Config struct {
    host string = "localhost"
    port int = 8080
    verbose bool = false
}

const Point struct {
    x, y int = 0
    z int = 1
}

When a struct is created with new() or a struct literal that omits a field, the default value is used instead of zero-initialization. #json structs cannot have default field values.

Scope

• Update the symbol scanner in symbols.ts to handle field type = value syntax when parsing struct fields
• Ensure hover/completion for struct fields includes the default value when present

[SchoolyB]

Implemented in cc34fce. This was filed as missing support, but the existing scanner had an active bug worth recording.

Grouped fields were silently corrupted. The field regex matched names and type as two loose groups, so:

const Point struct {
    x, y int = 0
    z int = 1
}

scanned as x typed "y int", and y was dropped entirely. Any hover or completion on a struct using grouped fields showed a field that did not exist and hid one that did. Defaults were separately discarded for all fields.

The scanner was rewritten to split the default off at the first = that is not ==, then parse comma-grouped names sharing one type. It also now tracks brace depth relative to the struct body, so struct-function bodies are no longer scanned as fields — previously a line like mut out int = self.x * factor inside a struct function was a candidate field.

Now scans as x/y/z, all int, defaults 0/0/1. Hover gains a Default column when any field declares one.

[SchoolyB]

The LSP half of this shipped earlier. The tree-sitter grammar also needed a change, now in grayscale-lang/tree-sitter-gray@0090150.

field_declaration was name type — no = expr and no comma-grouped names, so both host string = \"localhost\" and x, y int = 0 failed to parse. The rule now accepts repeated names and a default field.

The pinned grammar rev in zed-extension/extension.toml is updated, so Zed picks this up.

Verified against the 603 valid programs in the Grayscale integration suite: parse failures drop from 134 to 115 with zero regressions. The repository previously had no tests; test/corpus/features.txt now covers all seven features.