lang/rust: use rustic-mode instead on Emacs 26+

modules/lang/rust/config.el

@@ -1,16 +1,61 @@
 ;;; lang/rust/config.el -*- lexical-binding: t; -*-
 
-(after! rust-mode
-  (set-docsets! 'rust-mode "Rust")
+(def-package! rust-mode
+  :mode ("\\.rs$" . +rust|init)
+  :config
   (setq rust-indent-method-chain t)
 
+  (defun +rust|init ()
+    "Use `rustic-mode' if possible, otherwise fall back to `rust-mode'."
+    (if (and EMACS26+ (require 'rustic nil t))
+        (rustic-mode)
+      (rust-mode)))
+
+  (set-docsets! '(rust-mode rustic-mode) "Rust")
   (when (featurep! +lsp)
     (add-hook 'rust-mode-local-vars-hook #'lsp!))
 
-  (def-package! cargo
-    :defer t
-    :init
-    (map! :map rust-mode-map
+  ;; TODO PR these upstream
+  (after! dtrt-indent
+    (pushnew! dtrt-indent-hook-mapping-list
+              '(rust-mode default rust-indent-offset)
+              '(rustic-mode default rustic-indent-offset)))
+  (when (featurep! :tools editorconfig)
+    (after! editorconfig
+      (pushnew! editorconfig-indentation-alist
+                '(rust-mode rust-indent-offset)
+                '(rustic-mode rustic-indent-offset)))))
+
+
+(def-package! racer
+  :unless (featurep! +lsp)
+  :hook ((rust-mode rustic-mode) . racer-mode)
+  :config
+  (set-lookup-handlers! 'rust-mode
+    :definition '(racer-find-definition :async t)
+    :documentation '+rust-racer-lookup-documentation))
+
+
+(def-package! rustic
+  :when EMACS26+
+  :after rust-mode
+  :config
+  (setq rustic-indent-method-chain rust-indent-method-chain
+        rustic-flycheck-setup-mode-line-p nil
+        rustic-rls-pkg (featurep! +lsp)))
+
+
+;;
+;;; Tools
+
+(def-package! cargo
+  :after rust-mode
+  :config
+  (defvar +rust-keymap
+    (if (boundp 'rustic-mode-map)
+        rustic-mode-map
+      rust-mode-map))
+  (map! :map +rust-keymap
         :localleader
         (:prefix "b"
           :desc "cargo add"    "a" #'cargo-process-add
@@ -25,20 +70,4 @@
         (:prefix ("t" . "cargo test")
           :desc "all"          "a" #'cargo-process-test
           :desc "current file" "f" #'cargo-process-current-file-tests
-            :desc "current test" "t" #'cargo-process-current-test))))
-
-
-(def-package! racer
-  :unless (featurep! +lsp)
-  :after rust-mode
-  :config
-  (add-hook 'rust-mode-hook #'racer-mode)
-  (set-lookup-handlers! 'rust-mode
-    :definition '(racer-find-definition :async t)
-    :documentation '+rust-racer-lookup-documentation))
-
-
-(def-package! flycheck-rust
-  :when (featurep! :tools flycheck)
-  :after rust-mode
-  :config (add-hook 'rust-mode-hook #'flycheck-rust-setup))
+          :desc "current test" "t" #'cargo-process-current-test)))

modules/lang/rust/packages.el

@@ -1,11 +1,13 @@
 ;; -*- no-byte-compile: t; -*-
 ;;; lang/rust/packages.el
 
+(when EMACS26+
+  (package! rustic))
 (package! rust-mode)
-(package! cargo)
-
 (when (featurep! :tools flycheck)
   (package! flycheck-rust))
-
 (unless (featurep! +lsp)
   (package! racer))
+
+;;
+(package! cargo)