using(ast): add AST prelude merge mode (NYASH_USING_AST=1); strip-only collector; combine Program ASTs; prep for parser fix. Also keep legacy inlining default.

src/runner/modes/common.rs

@@ -49,13 +49,36 @@ impl NyashRunner {
             println!("\n🚀 Parsing and executing...\n");
         }
 
-        // Optional Phase-15: strip `using` lines (gate) for minimal acceptance
+        // Using handling: either strip+inline (legacy) or AST-based prelude merge (when NYASH_USING_AST=1)
+        let use_ast = std::env::var("NYASH_USING_AST").ok().as_deref() == Some("1");
         let mut code_ref: &str = &code;
         let cleaned_code_owned;
+        let mut prelude_asts: Vec<nyash_rust::ast::ASTNode> = Vec::new();
         if crate::config::env::enable_using() {
-            match crate::runner::modes::common_util::resolve::strip_using_and_register(self, &code, filename) {
-                Ok(s) => { cleaned_code_owned = s; code_ref = &cleaned_code_owned; }
-                Err(e) => { eprintln!("❌ {}", e); std::process::exit(1); }
+            if use_ast {
+                match crate::runner::modes::common_util::resolve::collect_using_and_strip(self, &code, filename) {
+                    Ok((clean, paths)) => {
+                        cleaned_code_owned = clean; code_ref = &cleaned_code_owned;
+                        // Parse each prelude file into AST and store
+                        for p in paths {
+                            match std::fs::read_to_string(&p) {
+                                Ok(src) => {
+                                    match NyashParser::parse_from_string(&src) {
+                                        Ok(ast) => prelude_asts.push(ast),
+                                        Err(e) => { eprintln!("❌ Parse error in using prelude {}: {}", p, e); std::process::exit(1); }
+                                    }
+                                }
+                                Err(e) => { eprintln!("❌ Error reading using prelude {}: {}", p, e); std::process::exit(1); }
+                            }
+                        }
+                    }
+                    Err(e) => { eprintln!("❌ {}", e); std::process::exit(1); }
+                }
+            } else {
+                match crate::runner::modes::common_util::resolve::strip_using_and_register(self, &code, filename) {
+                    Ok(s) => { cleaned_code_owned = s; code_ref = &cleaned_code_owned; }
+                    Err(e) => { eprintln!("❌ {}", e); std::process::exit(1); }
+                }
             }
         }
         // Optional dev sugar: @name[:T] = expr → local name[:T] = expr (line-head only)
@@ -69,10 +92,22 @@ impl NyashRunner {
         // Parse the code with debug fuel limit
         let groups = self.config.as_groups();
         eprintln!("🔍 DEBUG: Starting parse with fuel: {:?}...", groups.debug.debug_fuel);
-        let ast = match NyashParser::parse_from_string_with_fuel(code_ref, groups.debug.debug_fuel) {
+        let main_ast = match NyashParser::parse_from_string_with_fuel(code_ref, groups.debug.debug_fuel) {
             Ok(ast) => { eprintln!("🔍 DEBUG: Parse completed, AST created"); ast },
             Err(e) => { eprintln!("❌ Parse error: {}", e); process::exit(1); }
         };
+        // When using AST prelude mode, combine prelude ASTs + main AST into one Program
+        let ast = if use_ast && !prelude_asts.is_empty() {
+            use nyash_rust::ast::ASTNode;
+            let mut combined: Vec<ASTNode> = Vec::new();
+            for a in prelude_asts {
+                if let ASTNode::Program { statements, .. } = a { combined.extend(statements); }
+            }
+            if let ASTNode::Program { statements, .. } = main_ast.clone() {
+                combined.extend(statements);
+            }
+            ASTNode::Program { statements: combined, span: nyash_rust::ast::Span::unknown() }
+        } else { main_ast };
 
         // Stage-0: import loader (top-level only) — resolve path and register in modules registry
         if let nyash_rust::ast::ASTNode::Program { statements, .. } = &ast {

src/runner/modes/common_util/resolve/strip.rs

@@ -423,6 +423,86 @@ pub fn strip_using_and_register(
     Ok(preexpand_at_local(&combined))
 }
 
+/// Collect using targets and strip using lines, without inlining.
+/// Returns (cleaned_source, prelude_paths) where prelude_paths are resolved file paths
+/// to be parsed separately and AST-merged (when NYASH_USING_AST=1).
+pub fn collect_using_and_strip(
+    runner: &NyashRunner,
+    code: &str,
+    filename: &str,
+) -> Result<(String, Vec<String>), String> {
+    if !crate::config::env::enable_using() {
+        return Ok((code.to_string(), Vec::new()));
+    }
+    let using_ctx = runner.init_using_context();
+    let strict = std::env::var("NYASH_USING_STRICT").ok().as_deref() == Some("1");
+    let verbose = crate::config::env::cli_verbose()
+        || std::env::var("NYASH_RESOLVE_TRACE").ok().as_deref() == Some("1");
+    let ctx_dir = std::path::Path::new(filename).parent();
+
+    let mut out = String::with_capacity(code.len());
+    let mut prelude_paths: Vec<String> = Vec::new();
+    for line in code.lines() {
+        let t = line.trim_start();
+        if t.starts_with("using ") {
+            crate::cli_v!("[using] stripped line: {}", line);
+            let rest0 = t.strip_prefix("using ").unwrap().trim();
+            let rest0 = rest0.split('#').next().unwrap_or(rest0).trim();
+            let rest0 = rest0.strip_suffix(';').unwrap_or(rest0).trim();
+            let (target, alias) = if let Some(pos) = rest0.find(" as ") {
+                (rest0[..pos].trim().to_string(), Some(rest0[pos + 4..].trim().to_string()))
+            } else { (rest0.to_string(), None) };
+            let is_path = target.starts_with('"') || target.starts_with("./") || target.starts_with('/') || target.ends_with(".nyash");
+            if is_path {
+                let path = target.trim_matches('"').to_string();
+                // Resolve relative to current file dir
+                let mut p = std::path::PathBuf::from(&path);
+                if p.is_relative() {
+                    if let Some(dir) = ctx_dir { let cand = dir.join(&p); if cand.exists() { p = cand; } }
+                }
+                prelude_paths.push(p.to_string_lossy().to_string());
+                continue;
+            }
+            // Resolve namespaces/packages
+            match crate::runner::pipeline::resolve_using_target(
+                &target,
+                false,
+                &using_ctx.pending_modules,
+                &using_ctx.using_paths,
+                &using_ctx.aliases,
+                &using_ctx.packages,
+                ctx_dir,
+                strict,
+                verbose,
+            ) {
+                Ok(value) => {
+                    // Only file paths are candidates for AST prelude merge
+                    if value.ends_with(".nyash") || value.contains('/') || value.contains('\\') {
+                        // Resolve relative
+                        let mut p = std::path::PathBuf::from(&value);
+                        if p.is_relative() {
+                            if let Some(dir) = ctx_dir { let cand = dir.join(&p); if cand.exists() { p = cand; } }
+                        }
+                        prelude_paths.push(p.to_string_lossy().to_string());
+                    }
+                }
+                Err(e) => return Err(format!("using: {}", e)),
+            }
+            continue;
+        }
+        out.push_str(line);
+        out.push('\n');
+    }
+    // Optional prelude boundary comment (helps manual inspection; parser ignores comments)
+    if std::env::var("NYASH_RESOLVE_SEAM_DEBUG").ok().as_deref() == Some("1") {
+        let mut with_marker = String::with_capacity(out.len() + 64);
+        with_marker.push_str("\n/* --- using boundary (AST) --- */\n");
+        with_marker.push_str(&out);
+        out = with_marker;
+    }
+    Ok((out, prelude_paths))
+}
+
 /// Pre-expand line-head `@name[: Type] = expr` into `local name[: Type] = expr`.
 /// Minimal, safe, no semantics change. Applies only at line head (after spaces/tabs).
 pub fn preexpand_at_local(src: &str) -> String {