Split import syntax parser

Author: Milky2018

compose/imports.mbt

@@ -52,11 +52,12 @@ using @resolver {
 using @ast {type WgslDirective, type WgslDirectiveKind}
 
 ///|
-using @parser {
-  type WgslParseError,
+using @parser {type WgslParseError, parse_wgsl_translation_unit_strict}
+
+///|
+using @import_syntax {
   parse_wgsl_import_spec_is_empty_or_final_semicolon,
   parse_wgsl_import_targets,
-  parse_wgsl_translation_unit_strict,
 }
 
 ///|

compose/moon.pkg

@@ -7,6 +7,7 @@ import {
   "Milky2018/moon_wgsl/ast",
   "Milky2018/moon_wgsl/directive",
   "Milky2018/moon_wgsl/directive_syntax",
+  "Milky2018/moon_wgsl/import_syntax",
   "Milky2018/moon_wgsl/parser",
   "Milky2018/moon_wgsl/lex",
   "moonbitlang/core/hashmap",

docs/moon_wgsl-issue-tracker.md

@@ -13,6 +13,7 @@ Last updated: 2026-05-06
 
 | ID | Source | Problem | Status | Notes |
 | --- | --- | --- | --- | --- |
+| `WGSL-188` | Architecture review | `parser` still publicly owned `#import` payload parsing and `ParseImportsError`, so preprocessor/import syntax errors were attached to the WGSL translation-unit parser boundary. | `DONE` | Split import target parsing into `import_syntax` with its own moonyacc grammar, rewired compose/resolver/transform to depend on it, and removed import payload parsing from parser. Verified with the full local gate on 2026-05-06. |
 | `WGSL-187` | Architecture review | After moving one-line directive parsing out of `parser`, `parser` still depended on the broad `directive` package, pulling source scanning and shader-def semantics into the parser dependency surface. | `DONE` | Split low-level directive line / GLSL version parsing into `directive_syntax`, rewired parser and directive to depend on that narrow package, and kept source scanning plus shader-def/reference semantics in `directive`. Verified with the full local gate on 2026-05-06. |
 | `WGSL-186` | Architecture review | `directive` still depended on `parser` solely for one-line directive parsing, which forced `parser` to keep a public preprocessing directive entry point and retained a generated yacc start symbol for non-WGSL source-scanner work. | `DONE` | Moved one-line directive parsing into `directive`, removed the parser-to-directive generated start rule and tokens, rewired parser internals to consume the directive package, and dropped the reverse `directive -> parser` dependency. Verified with the full local gate on 2026-05-06. |
 | `WGSL-185` | Architecture review | AST still exposed zero-production-use type spelling/span convenience methods (`WgslTypeAtom::text`, `WgslTypeRef::start`), leaving raw type text and unused span access on the public surface after type atoms became structured. | `DONE` | Demoted `WgslTypeAtom::text` to package-private, removed unused public `WgslTypeRef::start`, regenerated interfaces, and verified `moon ide analyze` no longer reports public functions with zero usage. Verified with the full local gate on 2026-05-06. |