Merge #5758

5758: SSR: Explicitly autoderef and ref placeholders as needed r=matklad a=davidlattimore

Structural search replace now inserts *, & and &mut in the replacement to match any auto[de]ref in the matched code.

e.g. `$a.foo() ==>> bar($a)` might convert `x.foo()` to `bar(&mut x)`

Co-authored-by: David Lattimore <[email protected]>

1 files changed, 48 insertions, 2 deletions

diff --git a/crates/ssr/src/replacing.rs b/crates/ssr/src/replacing.rs
index 8f8fe6149..29284e3f1 100644
--- a/crates/ssr/src/replacing.rs
+++ b/crates/ssr/src/replacing.rs
@@ -1,10 +1,11 @@
 //! Code for applying replacement templates for matches that have previously been found.
 
-use crate::matching::Var;
 use crate::{resolving::ResolvedRule, Match, SsrMatches};
+use itertools::Itertools;
 use rustc_hash::{FxHashMap, FxHashSet};
 use syntax::ast::{self, AstToken};
 use syntax::{SyntaxElement, SyntaxKind, SyntaxNode, SyntaxToken, TextRange, TextSize};
+use test_utils::mark;
 use text_edit::TextEdit;
 
 /// Returns a text edit that will replace each match in `matches` with its corresponding replacement
@@ -114,11 +115,33 @@ impl ReplacementRenderer<'_> {
     fn render_token(&mut self, token: &SyntaxToken) {
         if let Some(placeholder) = self.rule.get_placeholder(&token) {
             if let Some(placeholder_value) =
-                self.match_info.placeholder_values.get(&Var(placeholder.ident.to_string()))
+                self.match_info.placeholder_values.get(&placeholder.ident)
             {
                 let range = &placeholder_value.range.range;
                 let mut matched_text =
                     self.file_src[usize::from(range.start())..usize::from(range.end())].to_owned();
+                // If a method call is performed directly on the placeholder, then autoderef and
+                // autoref will apply, so we can just substitute whatever the placeholder matched to
+                // directly. If we're not applying a method call, then we need to add explicitly
+                // deref and ref in order to match whatever was being done implicitly at the match
+                // site.
+                if !token_is_method_call_receiver(token)
+                    && (placeholder_value.autoderef_count > 0
+                        || placeholder_value.autoref_kind != ast::SelfParamKind::Owned)
+                {
+                    mark::hit!(replace_autoref_autoderef_capture);
+                    let ref_kind = match placeholder_value.autoref_kind {
+                        ast::SelfParamKind::Owned => "",
+                        ast::SelfParamKind::Ref => "&",
+                        ast::SelfParamKind::MutRef => "&mut ",
+                    };
+                    matched_text = format!(
+                        "{}{}{}",
+                        ref_kind,
+                        "*".repeat(placeholder_value.autoderef_count),
+                        matched_text
+                    );
+                }
                 let edit = matches_to_edit_at_offset(
                     &placeholder_value.inner_matches,
                     self.file_src,
@@ -179,6 +202,29 @@ impl ReplacementRenderer<'_> {
     }
 }
 
+/// Returns whether token is the receiver of a method call. Note, being within the receiver of a
+/// method call doesn't count. e.g. if the token is `$a`, then `$a.foo()` will return true, while
+/// `($a + $b).foo()` or `x.foo($a)` will return false.
+fn token_is_method_call_receiver(token: &SyntaxToken) -> bool {
+    use syntax::ast::AstNode;
+    // Find the first method call among the ancestors of `token`, then check if the only token
+    // within the receiver is `token`.
+    if let Some(receiver) =
+        token.ancestors().find_map(ast::MethodCallExpr::cast).and_then(|call| call.expr())
+    {
+        let tokens = receiver.syntax().descendants_with_tokens().filter_map(|node_or_token| {
+            match node_or_token {
+                SyntaxElement::Token(t) => Some(t),
+                _ => None,
+            }
+        });
+        if let Some((only_token,)) = tokens.collect_tuple() {
+            return only_token == *token;
+        }
+    }
+    false
+}
+
 fn parse_as_kind(code: &str, kind: SyntaxKind) -> Option<SyntaxNode> {
     use syntax::ast::AstNode;
     if ast::Expr::can_cast(kind) {