tools/lookup: Support type definition lookup handlers

modules/tools/lookup/autoload/lookup.el

@@ -18,6 +18,9 @@ properties:
 :implementations FN
   Run when looking for implementations of a symbol in the current project. Used
   by `+lookup/implementations'.
+:type-definition FN
+  Run when jumping to a symbol's type definition. Used by
+  `+lookup/type-definition'.
 :references FN
   Run when looking for usage references of a symbol in the current project. Used
   by `+lookup/references'.
@@ -49,8 +52,9 @@ change the current buffer or window or return non-nil when it succeeds.
 
 If it doesn't change the current buffer, or it returns nil, the lookup module
 will fall back to the next handler in `+lookup-definition-functions',
-`+lookup-implementations-functions', `+lookup-references-functions',
+`+lookup-implementations-functions', `+lookup-type-definition-functions',
-`+lookup-file-functions' or `+lookup-documentation-functions'.
+`+lookup-references-functions', `+lookup-file-functions' or
+`+lookup-documentation-functions'.
 
 Consecutive `set-lookup-handlers!' calls will overwrite previously defined
 handlers for MODES. If used on minor modes, they are stacked onto handlers
@@ -60,7 +64,7 @@ This can be passed nil as its second argument to unset handlers for MODES. e.g.
 
   (set-lookup-handlers! 'python-mode nil)
 
-\(fn MODES &key DEFINITION IMPLEMENTATIONS REFERENCES DOCUMENTATION FILE XREF-BACKEND ASYNC)"
+\(fn MODES &key DEFINITION IMPLEMENTATIONS TYPE-DEFINITION REFERENCES DOCUMENTATION FILE XREF-BACKEND ASYNC)"
   (declare (indent defun))
   (dolist (mode (doom-enlist modes))
     (let ((hook (intern (format "%s-hook" mode)))
@@ -72,17 +76,19 @@ This can be passed nil as its second argument to unset handlers for MODES. e.g.
         (fset
          fn
          (lambda ()
-           (cl-destructuring-bind (&key definition implementations references documentation file xref-backend async)
+           (cl-destructuring-bind (&key definition implementations type-definition references documentation file xref-backend async)
                plist
              (cl-mapc #'+lookup--set-handler
                       (list definition
                             implementations
+                            type-definition
                             references
                             documentation
                             file
                             xref-backend)
                       (list '+lookup-definition-functions
                             '+lookup-implementations-functions
+                            '+lookup-type-definition-functions
                             '+lookup-references-functions
                             '+lookup-documentation-functions
                             '+lookup-file-functions
@@ -139,6 +145,7 @@ This can be passed nil as its second argument to unset handlers for MODES. e.g.
          (handlers
           (plist-get (list :definition '+lookup-definition-functions
                            :implementations '+lookup-implementations-functions
+                           :type-definition '+lookup-type-definition-functions
                            :references '+lookup-references-functions
                            :documentation '+lookup-documentation-functions
                            :file '+lookup-file-functions)
@@ -259,6 +266,18 @@ the point or current buffer."
         ((+lookup--jump-to :implementations identifier nil arg))
         ((error "Couldn't find the implementations of %S" identifier))))
 
+;;;###autoload
+(defun +lookup/type-definition (identifier &optional arg)
+  "Jump to the type definition of IDENTIFIER (defaults to the symbol at point).
+
+Each function in `+lookup-type-definition-functions' is tried until one changes
+the point or current buffer."
+  (interactive (list (doom-thing-at-point-or-region)
+                     current-prefix-arg))
+  (cond ((null identifier) (user-error "Nothing under point"))
+        ((+lookup--jump-to :type-definition identifier nil arg))
+        ((error "Couldn't find the definition of %S" identifier))))
+
 ;;;###autoload
 (defun +lookup/references (identifier &optional arg)
   "Show a list of usages of IDENTIFIER (defaults to the symbol at point)

modules/tools/lookup/config.el

@@ -63,6 +63,15 @@ If the argument is interactive (satisfies `commandp'), it is called with
 argument: the identifier at point. See `set-lookup-handlers!' about adding to
 this list.")
 
+(defvar +lookup-type-definition-functions ()
+  "Functions for `+lookup/type-definition' to try. Stops at the first function to
+return non-nil or change the current window/point.
+
+If the argument is interactive (satisfies `commandp'), it is called with
+`call-interactively' (with no arguments). Otherwise, it is called with one
+argument: the identifier at point. See `set-lookup-handlers!' about adding to
+this list.")
+
 (defvar +lookup-references-functions
   '(+lookup-xref-references-backend-fn
     +lookup-project-search-backend-fn)

modules/tools/lsp/config.el

@@ -55,6 +55,7 @@ working on that project after closing the last buffer.")
     :documentation #'lsp-describe-thing-at-point
     :definition #'lsp-find-definition
     :implementations #'lsp-find-implementation
+    :type-definition #'lsp-find-type-definition
     :references #'lsp-find-references)
 
   ;; TODO Lazy load these. They don't need to be loaded all at once unless the