refactor: centralize box type metadata

src/mir/builder/plugin_sigs.rs

@@ -0,0 +1,41 @@
+use std::collections::HashMap;
+
+use super::super::MirType;
+
+/// Load plugin method signatures from `nyash_box.toml`.
+///
+/// Returns mapping `(BoxName, MethodName) -> MirType`.
+pub fn load_plugin_method_sigs() -> HashMap<(String, String), MirType> {
+    let mut sigs = HashMap::new();
+    if let Ok(content) = std::fs::read_to_string("nyash_box.toml") {
+        if let Ok(root) = toml::from_str::<toml::Value>(&content) {
+            if let Some(table) = root.as_table() {
+                for (box_name, box_val) in table {
+                    if let Some(methods) = box_val.get("methods").and_then(|v| v.as_table()) {
+                        for (mname, mval) in methods {
+                            if let Some(ret) = mval.get("returns") {
+                                let ty_str = ret.as_str().map(|s| s.to_string()).or_else(|| {
+                                    ret.get("type")
+                                        .and_then(|t| t.as_str())
+                                        .map(|s| s.to_string())
+                                });
+                                if let Some(ts) = ty_str {
+                                    let mir_ty = match ts.to_lowercase().as_str() {
+                                        "i64" | "int" | "integer" => MirType::Integer,
+                                        "f64" | "float" => MirType::Float,
+                                        "bool" | "boolean" => MirType::Bool,
+                                        "string" => MirType::String,
+                                        "void" | "unit" => MirType::Void,
+                                        other => MirType::Box(other.to_string()),
+                                    };
+                                    sigs.insert((box_name.clone(), mname.clone()), mir_ty);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+    sigs
+}