Fix accessor struct inlining in GOOPS

Fixes bug #17355.

* module/oop/goops.scm (memoize-effective-method!): Adapt to
  compute-effective-method change.
  (compute-effective-method, %compute-effective-method): Renamed from
  compute-cmethod; now a generic protocol.
  (compute-specialized-effective-method)
  (%compute-specialized-effective-method): New sub-protocol.
  (memoize-generic-function-application!): Adapt to call the hard-wired
  compute-applicable-methods based on the concrete arguments types --
  the semantics is that %compute-applicable-methods is the
  implementation for <generic> functions.  Perhaps we should do the same
  for sort-applicable-methods and method-more-specific?.
  (compute-getter-method, compute-setter-method): The standard
  #:procedure is now a generic slot-ref.  It wasn't valid to inline
  field access here, because subtypes could have different field
  layouts.
  (compute-applicable-methods): Refactor generic definition to use
  lexical scoping.
  (compute-specialized-effective-method): New method for
  <accessor-method>, which does field access inlining based on the
  concrete types being applied.

* test-suite/tests/goops.test ("accessor slots"): New test.

test-suite/tests/goops.test

@@ -621,3 +621,37 @@
   (pass-if-equal "<a>"
       (list <a> <b> <d> <c> <e> <f> <object> <top>)
     (compute-cpl <a>)))
+
+(with-test-prefix "accessor slots"
+  (let* ((a-accessor (make-accessor 'a))
+         (b-accessor (make-accessor 'b))
+         (<a> (class ()
+                (a #:init-keyword #:a #:accessor a-accessor)
+                #:name '<a>))
+         (<b> (class ()
+                (b #:init-keyword #:b #:accessor b-accessor)
+                #:name '<b>))
+         (<ab> (class (<a> <b>) #:name '<ab>))
+         (<ba> (class (<b> <a>) #:name '<ba>))
+         (<cab> (class (<ab>)
+                  (a #:init-keyword #:a)
+                  #:name '<cab>))
+         (<cba> (class (<ba>)
+                  (a #:init-keyword #:a)
+                  #:name '<cba>))
+         (a (make <a> #:a 'a))
+         (b (make <b> #:b 'b))
+         (ab (make <ab> #:a 'a #:b 'b))
+         (ba (make <ba> #:a 'a #:b 'b))
+         (cab (make <cab> #:a 'a #:b 'b))
+         (cba (make <cba> #:a 'a #:b 'b)))
+    (pass-if-equal "a accessor on a" 'a (a-accessor a))
+    (pass-if-equal "a accessor on ab" 'a (a-accessor ab))
+    (pass-if-equal "a accessor on ba" 'a (a-accessor ba))
+    (pass-if-equal "a accessor on cab" 'a (a-accessor cab))
+    (pass-if-equal "a accessor on cba" 'a (a-accessor cba))
+    (pass-if-equal "b accessor on a" 'b (b-accessor b))
+    (pass-if-equal "b accessor on ab" 'b (b-accessor ab))
+    (pass-if-equal "b accessor on ba" 'b (b-accessor ba))
+    (pass-if-equal "b accessor on cab" 'b (b-accessor cab))
+    (pass-if-equal "b accessor on cba" 'b (b-accessor cba))))