From 2fa0d4e2a86acb6beb5e95a0f438b8ce0b19097f Mon Sep 17 00:00:00 2001
From: Chayim Refael Friedman <chayimfr@gmail.com>
Date: Fri, 16 Aug 2024 10:50:17 +0300
Subject: [PATCH] When descending into macros in search, first check if there
 is a need to - i.e. if we are inside a macro call

This avoids the need to analyze the file when we are not inside a macro call.

This is especially important for the optimization in the next commit(s), as there the common case will be to descent into macros but then not analyze.
---
 crates/hir/src/semantics.rs | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/crates/hir/src/semantics.rs b/crates/hir/src/semantics.rs
index 3d6c985043..763f53031e 100644
--- a/crates/hir/src/semantics.rs
+++ b/crates/hir/src/semantics.rs
@@ -23,9 +23,11 @@ use hir_expand::{
     builtin::{BuiltinFnLikeExpander, EagerExpander},
     db::ExpandDatabase,
     files::InRealFile,
+    inert_attr_macro::find_builtin_attr_idx,
     name::AsName,
     FileRange, InMacroFile, MacroCallId, MacroFileId, MacroFileIdExt,
 };
+use intern::Symbol;
 use itertools::Itertools;
 use rustc_hash::{FxHashMap, FxHashSet};
 use smallvec::{smallvec, SmallVec};
@@ -674,6 +676,35 @@ impl<'db> SemanticsImpl<'db> {
         res
     }
 
+    fn is_inside_macro_call(token: &SyntaxToken) -> bool {
+        token.parent_ancestors().any(|ancestor| {
+            if ast::MacroCall::can_cast(ancestor.kind()) {
+                return true;
+            }
+            // Check if it is an item (only items can have macro attributes) that has a non-builtin attribute.
+            let Some(item) = ast::Item::cast(ancestor) else { return false };
+            item.attrs().any(|attr| {
+                let Some(meta) = attr.meta() else { return false };
+                let Some(path) = meta.path() else { return false };
+                let Some(attr_name) = path.as_single_name_ref() else { return true };
+                let attr_name = attr_name.text();
+                let attr_name = attr_name.as_str();
+                attr_name == "derive" || find_builtin_attr_idx(&Symbol::intern(attr_name)).is_none()
+            })
+        })
+    }
+
+    pub fn descend_into_macros_exact_if_in_macro(
+        &self,
+        token: SyntaxToken,
+    ) -> SmallVec<[SyntaxToken; 1]> {
+        if Self::is_inside_macro_call(&token) {
+            self.descend_into_macros_exact(token)
+        } else {
+            smallvec![token]
+        }
+    }
+
     pub fn descend_into_macros_cb(
         &self,
         token: SyntaxToken,