Improve support for R6/R7 SRFI module name formats.

Fixes <https://bugs.gnu.org/39601>.

Partly fixes <https://bugs.gnu.org/40371>.

It was already possible to import an SRFI module by referencing it
as (srfi :n) which is automatically translated to (srfi srfi-n), but
this conversion was only done during import.  After this change, it's
also possible to define a library as (srfi :n) which is automatically
translated to (srfi srfi-n) during definition.

It was not possible at all to define or import SRFI module names in the
R7RS format, (srfi n), where n is a non-negative exact integer.  It is
now possible both to define and import them as such, realized through
the same kind of conversion to a canonical (srfi srfi-n) name.

* module/ice-9/r6rs-libraries.scm: Numerous changes.

module/ice-9/r6rs-libraries.scm

@@ -20,7 +20,53 @@
 ;; This file is included from boot-9.scm and assumes the existence of (and 
 ;; expands into) procedures and syntactic forms defined therein.
 
+;; Note that we can't use top-level define for helpers here as it will
+;; pollute the (guile) module.
+
 (define (resolve-r6rs-interface import-spec)
+  (define (sym? stx)
+    (symbol? (syntax->datum stx)))
+
+  (define (n? stx)
+    (let ((n (syntax->datum stx)))
+      (and (exact-integer? n)
+           (not (negative? n)))))
+
+  (define (colon-n? x)
+    (let ((sym (syntax->datum x)))
+      (and (symbol? sym)
+           (let ((str (symbol->string sym)))
+             (and (string-prefix? ":" str)
+                  (let ((num (string->number (substring str 1))))
+                    (and (exact-integer? num)
+                         (not (negative? num)))))))))
+
+  (define (srfi-name? stx)
+    (syntax-case stx (srfi)
+      ((srfi n rest ...)
+       (and (and-map sym? #'(rest ...))
+            (or (n? #'n)
+                (colon-n? #'n))))
+      (_ #f)))
+
+  (define (module-name? stx)
+    (or (srfi-name? stx)
+        (syntax-case stx ()
+          ((name name* ...)
+           (and-map sym? #'(name name* ...)))
+          (_ #f))))
+
+  (define (make-srfi-n context n)
+    (datum->syntax
+     context
+     (string->symbol
+      (string-append
+       "srfi-"
+       (let ((n (syntax->datum n)))
+         (if (symbol? n)
+             (substring (symbol->string n) 1)
+             (number->string n)))))))
+
   (define (make-custom-interface mod)
     (let ((iface (make-module)))
       (set-module-kind! iface 'custom-interface)
@@ -37,27 +83,13 @@
     (for-each (lambda (mod)
                 (module-for-each f mod))
               (module-and-uses mod)))
-  (define (sym? x) (symbol? (syntax->datum x)))
 
   (syntax-case import-spec (library only except prefix rename srfi)
     ;; (srfi :n ...) -> (srfi srfi-n ...)
     ;; (srfi n ...) -> (srfi srfi-n ...)
     ((library (srfi n rest ... (version ...)))
-     (and (and-map sym? #'(srfi rest ...))
+     (srfi-name? #'(srfi n rest ...))
-          (or (and
+     (let ((srfi-n (make-srfi-n #'srfi #'n)))
-               (symbol? (syntax->datum #'n))
-               (let ((str (symbol->string (syntax->datum #'n))))
-                 (and (string-prefix? ":" str)
-                      (and=> (string->number (substring str 1))
-                             exact-integer?))))
-              (exact-integer? (syntax->datum #'n))))
-     (let ((srfi-n (string->symbol
-                    (string-append
-                     "srfi-"
-                     (let ((n (syntax->datum #'n)))
-                       (if (symbol? n)
-                           (substring (symbol->string n) 1)
-                           (number->string n)))))))
        (resolve-r6rs-interface
         (syntax-case #'(rest ...) ()
           (()
@@ -152,15 +184,58 @@
              (lp (cdr in) (cons (vector to replace? var) out))))))))
     
     ((name name* ... (version ...))
-     (and-map sym? #'(name name* ...))
+     (module-name? #'(name name* ...))
      (resolve-r6rs-interface #'(library (name name* ... (version ...)))))
 
     ((name name* ...)
-     (and-map sym? #'(name name* ...))
+     (module-name? #'(name name* ...))
      (resolve-r6rs-interface #'(library (name name* ... ()))))))
 
 (define-syntax library
   (lambda (stx)
+    (define (sym? stx)
+      (symbol? (syntax->datum stx)))
+
+    (define (n? stx)
+      (let ((n (syntax->datum stx)))
+        (and (exact-integer? n)
+             (not (negative? n)))))
+
+    (define (colon-n? x)
+      (let ((sym (syntax->datum x)))
+        (and (symbol? sym)
+             (let ((str (symbol->string sym)))
+               (and (string-prefix? ":" str)
+                    (let ((num (string->number (substring str 1))))
+                      (and (exact-integer? num)
+                           (not (negative? num)))))))))
+
+    (define (srfi-name? stx)
+      (syntax-case stx (srfi)
+        ((srfi n rest ...)
+         (and (and-map sym? #'(rest ...))
+              (or (n? #'n)
+                  (colon-n? #'n))))
+        (_ #f)))
+
+    (define (module-name? stx)
+      (or (srfi-name? stx)
+          (syntax-case stx ()
+            ((name name* ...)
+             (and-map sym? #'(name name* ...)))
+            (_ #f))))
+
+    (define (make-srfi-n context n)
+      (datum->syntax
+       context
+       (string->symbol
+        (string-append
+         "srfi-"
+         (let ((n (syntax->datum n)))
+           (if (symbol? n)
+               (substring (symbol->string n) 1)
+               (number->string n)))))))
+
     (define (compute-exports ifaces specs)
       (define (re-export? sym)
         (or-map (lambda (iface) (module-variable iface sym)) ifaces))
@@ -195,23 +270,34 @@
               (else
                (lp #'rest (cons #'id e) r x))))))))
 
-    (syntax-case stx (export import)
+    (syntax-case stx (export import srfi)
       ((_ (name name* ...)
           (export espec ...)
           (import ispec ...)
           body ...)
-       (and-map identifier? #'(name name* ...))
+       (module-name? #'(name name* ...))
        ;; Add () as the version.
        #'(library (name name* ... ())
            (export espec ...)
            (import ispec ...)
            body ...))
 
+      ((_ (srfi n rest ... (version ...))
+          (export espec ...)
+          (import ispec ...)
+          body ...)
+       (srfi-name? #'(srfi n rest ...))
+       (let ((srfi-n (make-srfi-n #'srfi #'n)))
+         #`(library (srfi #,srfi-n rest ... (version ...))
+             (export espec ...)
+             (import ispec ...)
+             body ...)))
+
       ((_ (name name* ... (version ...))
           (export espec ...)
           (import ispec ...)
 	  body ...)
-       (and-map identifier? #'(name name* ...))
+       (module-name? #'(name name* ...))
        (call-with-values
            (lambda ()
              (compute-exports