textDocument/rename Filter out when symbol references itself

When a symbol is recorded to be its own reference, fennel-ls
accidentally counts the reference twice. That's fine, but we don't want
to replace the same words multiple times

src/fennel-ls/handlers.fnl

@@ -191,11 +191,14 @@ Every time the client sends a message, it gets handled by a function in the corr
       (let [usages (icollect [_ symbol (ipairs definition.referenced-by)
                               &into [{:range (message.multisym->range self def-file definition.binding 1)
                                       :newText new-name}]]
-                     {:newText new-name
-                      :range (message.multisym->range self def-file symbol 1)})]
+                     (if (not (rawequal symbol definition.binding))
+                       {:newText new-name
+                        :range (message.multisym->range self def-file symbol 1)}))]
+
         ;; NOTE: I don't care about encoding here because we just need the relative positions
-        (table.sort usages #(> (utils.position->byte def-file.text $1.range.start :utf-8)
-                               (utils.position->byte def-file.text $2.range.start :utf-8)))
+        (table.sort usages
+          #(> (utils.position->byte def-file.text $1.range.start :utf-8)
+              (utils.position->byte def-file.text $2.range.start :utf-8)))
         {:changes {def-file.uri usages}})
       (catch _ nil))))
 

src/fennel-ls/utils.fnl

@@ -157,6 +157,17 @@ WARNING: this is only used in the test code, not in the real language server"
 (λ type= [val typ]
   (= (type val) typ))
 
+(λ uniq-by [list eq?]
+  "I know the big O of this is bad, but we'll come back to it if it's a performance problem"
+  (let [result []]
+    (each [_ new-item (ipairs list)]
+      (if (not (accumulate [any? nil
+                            _ seen-item (ipairs result)
+                            &until any?]
+                 (eq? seen-item new-item)))
+        (table.insert result new-item)))
+    result))
+
 {: uri->path
  : path->uri
  : pos->position
@@ -166,4 +177,5 @@ WARNING: this is only used in the test code, not in the real language server"
  : apply-edits
  : multi-sym-split
  : get-ast-info
+ : uniq-by
  : type=}

test/rename-test.fnl

@@ -35,6 +35,8 @@
 
   (it "renames from destructure/args"
     (check-rename "(fn [{: x}] x)" 0 8 :foo "(fn [{: foo}] foo)")
-    (check-rename "(fn [{:x x}] x)" 0 9 :foo "(fn [{:x foo}] foo)")))
-
+    (check-rename "(fn [{:x x}] x)" 0 9 :foo "(fn [{:x foo}] foo)"))
 
+ (it "renames a sym inside of lambda"
+   (check-rename "(λ [foo] (print foo))" 0 6 :something
+                 "(λ [something] (print something))")))