Merge #8415

8415: Fix faulty assertion when extracting function with macro call r=matklad a=brandondong

**Reproduction:**
```rust
fn main() {
    let n = 1;
    let k = n * n;
    dbg!(n);
}
```
1. Select the second and third lines of the main function. Use the "Extract into function" code assist.
2. Panic occurs in debug, error is logged in release: "[ERROR ide_assists::handlers::extract_function] assertion failed: matches!(path, ast :: Expr :: PathExpr(_))".
3. Function generates successfully on release where the panic was bypassed.
```rust
fn fun_name(n: i32) {
    let k = n * n;
    dbg!(n);
}
```

**Cause:**
- The generated function will take `n` as a parameter. The extraction logic needs to search the usages of `n` to determine whether it is used mutably or not. The helper `path_element_of_reference` is called for each usage but the second usage is a macro call and fails the `Expr::PathExpr(_)` match assertion.
- The caller of `path_element_of_reference` does implicitly assume it to be a `Expr::PathExpr(_)` in how it looks at its parent node for determining whether it is used mutably. This logic will not work for macros.
- I'm not sure if there are any other cases besides macros where it could be something other than a `Expr::PathExpr(_)`. I tried various examples and could not find any.

**Fix:**
- Update assertion to include the macro case.
- Add a FIXME to properly handle checking if a macro usage requires mutable access. For now, return false instead of running the existing logic that is tailored for `Expr::PathExpr(_)`'s.

Co-authored-by: Brandon <[email protected]>

1 files changed, 46 insertions, 2 deletions

diff --git a/crates/ide_assists/src/handlers/extract_function.rs b/crates/ide_assists/src/handlers/extract_function.rs
index af9543766..059414274 100644
--- a/crates/ide_assists/src/handlers/extract_function.rs
+++ b/crates/ide_assists/src/handlers/extract_function.rs
@@ -736,6 +736,14 @@ fn reference_is_exclusive(
 
 /// checks if this expr requires `&mut` access, recurses on field access
 fn expr_require_exclusive_access(ctx: &AssistContext, expr: &ast::Expr) -> Option<bool> {
+    match expr {
+        ast::Expr::MacroCall(_) => {
+            // FIXME: expand macro and check output for mutable usages of the variable?
+            return None;
+        }
+        _ => (),
+    }
+
     let parent = expr.syntax().parent()?;
 
     if let Some(bin_expr) = ast::BinExpr::cast(parent.clone()) {
@@ -794,7 +802,7 @@ impl HasTokenAtOffset for SyntaxNode {
     }
 }
 
-/// find relevant `ast::PathExpr` for reference
+/// find relevant `ast::Expr` for reference
 ///
 /// # Preconditions
 ///
@@ -811,7 +819,11 @@ fn path_element_of_reference(
         stdx::never!(false, "cannot find path parent of variable usage: {:?}", token);
         None
     })?;
-    stdx::always!(matches!(path, ast::Expr::PathExpr(_)));
+    stdx::always!(
+        matches!(path, ast::Expr::PathExpr(_) | ast::Expr::MacroCall(_)),
+        "unexpected expression type for variable usage: {:?}",
+        path
+    );
     Some(path)
 }
 
@@ -3462,4 +3474,36 @@ fn foo() -> Result<(), i64> {
 }"##,
         );
     }
+
+    #[test]
+    fn param_usage_in_macro() {
+        check_assist(
+            extract_function,
+            r"
+macro_rules! m {
+    ($val:expr) => { $val };
+}
+
+fn foo() {
+    let n = 1;
+    $0let k = n * m!(n);$0
+    let m = k + 1;
+}",
+            r"
+macro_rules! m {
+    ($val:expr) => { $val };
+}
+
+fn foo() {
+    let n = 1;
+    let k = fun_name(n);
+    let m = k + 1;
+}
+
+fn $0fun_name(n: i32) -> i32 {
+    let k = n * m!(n);
+    k
+}",
+        );
+    }
 }