Add prettify configuration to the rust-ts-mode

[Christophe TROESTLER <Christophe.TROESTLER@umons.ac.be>]

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Hi,

I noticed that the rust-ts-mode does not have a configuration for the prettify-symbols-mode.  The attached patch aims to add that.

On another note, is it planned to have compile support for Rust?

Best regards,
Christophe

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From b9d3549810465aae90c5917b943e0393d6519485 Mon Sep 17 00:00:00 2001
From: Christophe Troestler <Christophe.Troestler@umons.ac.be>
Date: Mon, 11 Sep 2023 15:32:57 +0200
Subject: [PATCH] Add prettify configuration to rust-ts-mode
Content-Type: text/plain; charset="utf-8"

* lisp/progmodes/rust-ts-mode.el: Add prettify configuration to the mode.
---
 lisp/progmodes/rust-ts-mode.el | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/lisp/progmodes/rust-ts-mode.el b/lisp/progmodes/rust-ts-mode.el
index 999c1d7ae96..88344934e49 100644
--- a/lisp/progmodes/rust-ts-mode.el
+++ b/lisp/progmodes/rust-ts-mode.el
@@ -48,6 +48,12 @@ rust-ts-mode-indent-offset
   :safe 'integerp
   :group 'rust)
 
+(defvar rust-ts-mode-prettify-symbols-alist
+  '(("&&" . ?∧) ("||" . ?∨)
+    ("<=" . ?≤)  (">=" . ?≥) ("!=" . ?≠)
+    ("INFINITY" . ?∞) ("->" . ?→) ("=>" . ?⇒))
+  "Value for `prettify-symbols-alist' in `rust-ts-mode'.")
+
 (defvar rust-ts-mode--syntax-table
   (let ((table (make-syntax-table)))
     (modify-syntax-entry ?+   "."      table)
@@ -386,6 +392,19 @@ rust-ts-mode--syntax-propertize
                             (?< '(4 . ?>))
                             (?> '(5 . ?<))))))))
 
+(defun rust-ts-mode--prettify-symbols-compose-p (start end match)
+  "Return true iff the symbol MATCH should be composed.
+See `prettify-symbols-compose-predicate'."
+  (and (fboundp 'prettify-symbols-default-compose-p)
+       (prettify-symbols-default-compose-p start end match)
+       ;; Make sure || is not a closure with 0 arguments and && is not
+       ;; a double reference.
+       (pcase match
+         ((or "||" "&&")
+          (string= (treesit-node-field-name (treesit-node-at (point)))
+                   "operator"))
+         (_ t))))
+
 ;;;###autoload
 (define-derived-mode rust-ts-mode prog-mode "Rust"
   "Major mode for editing Rust, powered by tree-sitter."
@@ -411,6 +430,11 @@ rust-ts-mode
                     number type)
                   ( bracket delimiter error function operator property variable)))
 
+    ;; Prettify configuration
+    (setq prettify-symbols-alist rust-ts-mode-prettify-symbols-alist)
+    (setq prettify-symbols-compose-predicate
+          #'rust-ts-mode--prettify-symbols-compose-p)
+
     ;; Imenu.
     (setq-local treesit-simple-imenu-settings
                 `(("Module" "\\`mod_item\\'" nil nil)
-- 
2.40.1