Implement fix, add tests

2 files changed, 55 insertions, 28 deletions

diff --git a/crates/hir_ty/src/diagnostics.rs b/crates/hir_ty/src/diagnostics.rs
index b4cf81c10..3d7663f6a 100644
--- a/crates/hir_ty/src/diagnostics.rs
+++ b/crates/hir_ty/src/diagnostics.rs
@@ -392,7 +392,7 @@ impl Diagnostic for IncorrectCase {
 #[derive(Debug)]
 pub struct ReplaceFilterMapNextWithFindMap {
     pub file: HirFileId,
-    pub filter_map_expr: AstPtr<ast::Expr>,
+    /// This expression is the whole method chain up to and including `.filter_map(..).next()`.
     pub next_expr: AstPtr<ast::Expr>,
 }
 
@@ -404,7 +404,7 @@ impl Diagnostic for ReplaceFilterMapNextWithFindMap {
         "replace filter_map(..).next() with find_map(..)".to_string()
     }
     fn display_source(&self) -> InFile<SyntaxNodePtr> {
-        InFile { file_id: self.file, value: self.filter_map_expr.clone().into() }
+        InFile { file_id: self.file, value: self.next_expr.clone().into() }
     }
     fn as_any(&self) -> &(dyn Any + Send + 'static) {
         self
@@ -671,15 +671,55 @@ fn foo() { break; }
     }
 
     #[test]
-    fn replace_missing_filter_next_with_find_map() {
+    fn replace_filter_next_with_find_map() {
         check_diagnostics(
             r#"
             fn foo() {
-            let m = [1, 2, 3]
-                .iter()
-                .filter_map(|x| if *x == 2 { Some (4) } else { None })
-                .next();
-                //^^^ Replace .filter_map(..).next() with .find_map(..)
+                let m = [1, 2, 3].iter().filter_map(|x| if *x == 2 { Some (4) } else { None }).next();
+                      //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ replace filter_map(..).next() with find_map(..)
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn replace_filter_next_with_find_map_no_diagnostic_without_next() {
+        check_diagnostics(
+            r#"
+            fn foo() {
+                let m = [1, 2, 3]
+                    .iter()
+                    .filter_map(|x| if *x == 2 { Some (4) } else { None })
+                    .len();
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn replace_filter_next_with_find_map_no_diagnostic_with_intervening_methods() {
+        check_diagnostics(
+            r#"
+            fn foo() {
+                let m = [1, 2, 3]
+                    .iter()
+                    .filter_map(|x| if *x == 2 { Some (4) } else { None })
+                    .map(|x| x + 2)
+                    .len();
+            }
+            "#,
+        );
+    }
+
+    #[test]
+    fn replace_filter_next_with_find_map_no_diagnostic_if_not_in_chain() {
+        check_diagnostics(
+            r#"
+            fn foo() {
+                let m = [1, 2, 3]
+                    .iter()
+                    .filter_map(|x| if *x == 2 { Some (4) } else { None });
+                let n = m.next();
             }
             "#,
         );
diff --git a/crates/hir_ty/src/diagnostics/expr.rs b/crates/hir_ty/src/diagnostics/expr.rs
index 170d23178..b87557ff5 100644
--- a/crates/hir_ty/src/diagnostics/expr.rs
+++ b/crates/hir_ty/src/diagnostics/expr.rs
@@ -41,16 +41,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
         ExprValidator { owner, infer, sink }
     }
 
-    fn bar() {
-        // LOOK FOR THIS
-        let m = [1, 2, 3]
-            .iter()
-            .filter_map(|x| if *x == 2 { Some(4) } else { None })
-            .next();
-    }
-
     pub(super) fn validate_body(&mut self, db: &dyn HirDatabase) {
-        // DO NOT MERGE: just getting something working for now
         self.check_for_filter_map_next(db);
 
         let body = db.body(self.owner.into());
@@ -169,24 +160,20 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
 
         for (id, expr) in body.exprs.iter() {
             if let Expr::MethodCall { receiver, method_name, args, .. } = expr {
-                let method_name_hack_do_not_merge = format!("{}", method_name);
+                let method_name = format!("{}", method_name);
 
-                if method_name_hack_do_not_merge == "filter_map" && args.len() == 1 {
-                    prev = Some((id, args[0]));
+                if method_name == "filter_map" && args.len() == 1 {
+                    prev = Some(id);
                     continue;
                 }
 
-                if method_name_hack_do_not_merge == "next" {
-                    if let Some((filter_map_id, filter_map_args)) = prev {
+                if method_name == "next" {
+                    if let Some(filter_map_id) = prev {
                         if *receiver == filter_map_id {
                             let (_, source_map) = db.body_with_source_map(self.owner.into());
-                            if let (Ok(filter_map_source_ptr), Ok(next_source_ptr)) = (
-                                source_map.expr_syntax(filter_map_id),
-                                source_map.expr_syntax(id),
-                            ) {
+                            if let Ok(next_source_ptr) = source_map.expr_syntax(id) {
                                 self.sink.push(ReplaceFilterMapNextWithFindMap {
-                                    file: filter_map_source_ptr.file_id,
-                                    filter_map_expr: filter_map_source_ptr.value,
+                                    file: next_source_ptr.file_id,
                                     next_expr: next_source_ptr.value,
                                 });
                             }