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, 101 insertions, 0 deletions

diff --git a/mingling_pathf/src/patterns/group.rs b/mingling_pathf/src/patterns/group.rs
new file mode 100644
index 0000000..99d1137
--- /dev/null
+++ b/mingling_pathf/src/patterns/group.rs
@@ -0,0 +1,101 @@
+use syn::Item;
+
+use crate::pattern_analyzer::{AnalyzeItem, AnalyzePattern};
+
+/// Matches the `group!` and `group_structural!` macros.
+///
+/// Covered forms:
+/// - `group!(TypeName)`
+/// - `group!(Alias = path::Type)`
+/// - `group_structural!(TypeName)`
+/// - `group_structural!(Alias = path::Type)`
+pub struct GroupPattern;
+
+impl AnalyzePattern for GroupPattern {
+    fn contains(&self, content: &str) -> bool {
+        content.contains("group!") || content.contains("group_structural!")
+    }
+
+    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 {
+                Item::Macro(m) => {
+                    let Some(last) = m.mac.path.segments.last() else {
+                        continue;
+                    };
+                    let macro_name = last.ident.to_string();
+                    if macro_name != "group" && macro_name != "group_structural" {
+                        continue;
+                    }
+                    if let Some(name) = extract_group_name(&m.mac.tokens) {
+                        items.push(AnalyzeItem {
+                            module: String::new(),
+                            item_name: name,
+                        });
+                    }
+                }
+                Item::Mod(item_mod) => {
+                    if let Some((_, nested)) = &item_mod.content {
+                        for n in nested {
+                            if let Item::Macro(m) = n {
+                                let Some(last) = m.mac.path.segments.last() else {
+                                    continue;
+                                };
+                                let macro_name = last.ident.to_string();
+                                if macro_name != "group" && macro_name != "group_structural" {
+                                    continue;
+                                }
+                                if let Some(name) = extract_group_name(&m.mac.tokens) {
+                                    items.push(AnalyzeItem {
+                                        module: item_mod.ident.to_string(),
+                                        item_name: name,
+                                    });
+                                }
+                            }
+                        }
+                    }
+                }
+                _ => {}
+            }
+        }
+
+        items
+    }
+}
+
+/// Extract the alias / type name from the arguments of `group!`.
+///
+/// - `group!(ParseIntError)` → `ParseIntError`
+/// - `group!(ErrorIo = std::io::Error)` → `ErrorIo`
+fn extract_group_name(tokens: &proc_macro2::TokenStream) -> Option<String> {
+    let stream = tokens.clone();
+    let mut iter = stream.into_iter();
+
+    loop {
+        match iter.next()? {
+            proc_macro2::TokenTree::Ident(ident) => {
+                let name = ident.to_string();
+
+                // Check if there is a `=` following
+                let next = iter.next();
+                match next {
+                    Some(proc_macro2::TokenTree::Punct(p)) if p.as_char() == '=' => {
+                        // group!(Alias = path::Type)
+                        return Some(name);
+                    }
+                    _ => {
+                        // group!(TypeName)
+                        return Some(name);
+                    }
+                }
+            }
+            _ => continue,
+        }
+    }
+}