builder: split MirBuilder core methods

src/mir/builder/builder_method_index.rs

@@ -0,0 +1,58 @@
+use super::MirBuilder;
+
+impl MirBuilder {
+    // ----------------------
+    // Method tail index (performance helper)
+    // ----------------------
+    fn rebuild_method_tail_index(&mut self) {
+        self.comp_ctx.method_tail_index.clear();
+        if let Some(ref module) = self.current_module {
+            for name in module.functions.keys() {
+                if let (Some(dot), Some(slash)) = (name.rfind('.'), name.rfind('/')) {
+                    if slash > dot {
+                        let tail = &name[dot..];
+                        self.comp_ctx
+                            .method_tail_index
+                            .entry(tail.to_string())
+                            .or_insert_with(Vec::new)
+                            .push(name.clone());
+                    }
+                }
+            }
+            self.comp_ctx.method_tail_index_source_len = module.functions.len();
+        } else {
+            self.comp_ctx.method_tail_index_source_len = 0;
+        }
+    }
+
+    fn ensure_method_tail_index(&mut self) {
+        let need_rebuild = match self.current_module {
+            Some(ref refmod) => {
+                self.comp_ctx.method_tail_index_source_len != refmod.functions.len()
+            }
+            None => self.comp_ctx.method_tail_index_source_len != 0,
+        };
+        if need_rebuild {
+            self.rebuild_method_tail_index();
+        }
+    }
+
+    pub(super) fn method_candidates(&mut self, method: &str, arity: usize) -> Vec<String> {
+        self.ensure_method_tail_index();
+        let tail = format!(".{}{}", method, format!("/{}", arity));
+        self.comp_ctx
+            .method_tail_index
+            .get(&tail)
+            .cloned()
+            .unwrap_or_default()
+    }
+
+    pub(super) fn method_candidates_tail<S: AsRef<str>>(&mut self, tail: S) -> Vec<String> {
+        self.ensure_method_tail_index();
+        self.comp_ctx
+            .method_tail_index
+            .get(tail.as_ref())
+            .cloned()
+            .unwrap_or_default()
+    }
+}