Looks like a mistake in docstring:

* lisp/progmodes/compile.el (compilation-mode-map)

Remove mention of compilation-minor-mode-map as comment in the body says

;; Don't inherit from compilation-minor-mode-map,
;; because that introduces a menu bar item we don't want.
;; That confuses C-down-mouse-3.

and the map actually inherits from special-mode-map
---
 lisp/progmodes/compile.el | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/lisp/progmodes/compile.el b/lisp/progmodes/compile.el
index 13b672bd53..7ac5405ab1 100644
--- a/lisp/progmodes/compile.el
+++ b/lisp/progmodes/compile.el
@@ -2090,8 +2090,7 @@ define-key map [menu-bar compilation compilation-compile]
       '(menu-item "Compile..." compile
 		  :help "Compile the program including the current buffer.  Default: run `make'"))
     map)
-  "Keymap for compilation log buffers.
-`compilation-minor-mode-map' is a parent of this.")
+  "Keymap for compilation log buffers.")
 
 (defvar compilation-mode-tool-bar-map
   ;; When bootstrapping, tool-bar-map is not properly initialized yet,
-- 
2.26.2