feat(pathf): add build-time type path resolution system

Add `mingling_pathf` sub-crate and `pathf` feature for automatic
resolution of Mingling type module paths at build time. Scans source
files, identifies macro invocations via pattern matchers, and generates
mapping files consumed by `gen_program!()`.

1 files changed, 103 insertions, 0 deletions

diff --git a/mingling_pathf/src/patterns/pack.rs b/mingling_pathf/src/patterns/pack.rs
new file mode 100644
index 0000000..f025f7d
--- /dev/null
+++ b/mingling_pathf/src/patterns/pack.rs
@@ -0,0 +1,103 @@
+use syn::Item;
+
+use crate::pattern_analyzer::{AnalyzeItem, AnalyzePattern};
+
+/// Matches types defined by `pack!`, `pack_err!`, `pack_structural!`, `pack_err_structural!` macros.
+///
+/// Covered forms:
+/// - `pack!(TypeName = InnerType)`
+/// - `pack! { TypeName = InnerType }`
+/// - `pack_err!(TypeName)`
+/// - `pack_err!(TypeName = InnerType)`
+/// - `pack_structural!` series same as above
+pub struct PackPattern;
+
+impl AnalyzePattern for PackPattern {
+    fn contains(&self, content: &str) -> bool {
+        content.contains("pack!") || content.contains("pack_err!")
+    }
+
+    fn analyze(&self, content: &str) -> Vec<AnalyzeItem> {
+        let Ok(syntax) = syn::parse_file(content) else {
+            return Vec::new();
+        };
+
+        let mut items = Vec::new();
+
+        for item in &syntax.items {
+            match item {
+                // Top-level macro calls
+                Item::Macro(m) => {
+                    if let Some(name) = try_extract_pack_name(m) {
+                        items.push(AnalyzeItem {
+                            module: String::new(),
+                            item_name: name,
+                        });
+                    }
+                }
+                // Macro calls inside inline modules
+                Item::Mod(item_mod) => {
+                    if let Some((_, nested)) = &item_mod.content {
+                        for n in nested {
+                            if let Item::Macro(m) = n
+                                && let Some(name) = try_extract_pack_name(m) {
+                                    items.push(AnalyzeItem {
+                                        module: item_mod.ident.to_string(),
+                                        item_name: name,
+                                    });
+                                }
+                        }
+                    }
+                }
+                _ => {}
+            }
+        }
+
+        items
+    }
+}
+
+/// If the macro call is `pack!` / `pack_err!` / etc., extract the registered type name.
+fn try_extract_pack_name(m: &syn::ItemMacro) -> Option<String> {
+    let macro_name = m.mac.path.segments.last()?.ident.to_string();
+
+    match macro_name.as_str() {
+        "pack" | "pack_err" | "pack_structural" | "pack_err_structural" => {}
+        _ => return None,
+    }
+
+    let tokens = &m.mac.tokens;
+
+    // `pack!(T)` or `pack!(T = U)` — the first ident is the type name
+    // Parse simply with syn
+    if let Ok(ident) = syn::parse2::<syn::Ident>(tokens.clone()) {
+        // pack!(TypeName) — just a single ident
+        return Some(ident.to_string());
+    }
+
+    // Try to parse `Ident = Type`
+    // Clone tokens first to avoid partial consumption
+    let stream = tokens.clone();
+    let mut iter = stream.into_iter();
+
+    // Skip leading attributes/doc comments
+    loop {
+        match iter.next()? {
+            proc_macro2::TokenTree::Ident(ident) => {
+                // Found the first ident, this is the type name
+                let type_name = ident.to_string();
+
+                // Check if `=` follows
+                if let Some(proc_macro2::TokenTree::Punct(p)) = iter.next()
+                    && p.as_char() == '=' {
+                        // pack!(TypeName = InnerType)
+                        return Some(type_name);
+                    }
+
+                // pack_err!(TypeName) — only a single ident
+                return Some(type_name);
+            }
+            _ => continue,
+        }
+    }
+}