add source:line-for-user, returning a 1-indexed line number

* module/system/vm/program.scm (source:line-for-user): New exported
  procedure, returns a 1-indexed line, suitable for presentation to a
  user.
  (write-program): Use source:line-for-user when making fallback names.

* module/system/vm/coverage.scm (coverage-data->lcov):
* module/language/assembly/disassemble.scm (source->string):
* module/system/repl/debug.scm (print-frame): Use source:line-for-user.

module/language/assembly/disassemble.scm

@@ -113,7 +113,7 @@
 
 (define (source->string src)
   (format #f "~a:~a:~a" (or (source:file src) "(unknown file)")
-          (source:line src) (source:column src)))
+          (source:line-for-user src) (source:column src)))
 
 (define (make-int16 byte1 byte2)
   (+ (* byte1 256) byte2))

module/system/repl/debug.scm

@@ -109,7 +109,7 @@
         "unknown file"))
   (let* ((source (frame-source frame))
          (file (source:pretty-file source))
-         (line (and=> source source:line))
+         (line (and=> source source:line-for-user))
          (col (and=> source source:column)))
     (if (and file (not (equal? file (source:pretty-file last-source))))
         (format port "~&In ~a:~&" file))

module/system/vm/coverage.scm

@@ -332,10 +332,10 @@ gathered, even if their code was not executed."
     (and (program? proc)
          (let ((sources (program-sources* data proc)))
            (and (pair? sources)
-                (let* ((line (source:line (car sources)))
+                (let* ((line (source:line-for-user (car sources)))
                        (name (or (procedure-name proc)
-                                 (format #f "anonymous-l~a" (+ 1 line)))))
-                  (format port "FN:~A,~A~%" (+ 1 line) name)
+                                 (format #f "anonymous-l~a" line))))
+                  (format port "FN:~A,~A~%" line name)
                   (and=> (procedure-execution-count data proc)
                          (lambda (count)
                            (format port "FNDA:~A,~A~%" count name))))))))

module/system/vm/program.scm

@@ -28,6 +28,7 @@
             binding:start binding:end
 
             source:addr source:line source:column source:file
+            source:line-for-user
             program-sources program-source
 
             program-bindings program-bindings-by-index program-bindings-for-ip
@@ -64,6 +65,12 @@
 (define (source:column source)
   (cdddr source))
 
+;; Lines are zero-indexed inside Guile, but users expect them to be
+;; one-indexed. Columns, on the other hand, are zero-indexed to both. Go
+;; figure.
+(define (source:line-for-user source)
+  (1+ (source:line source)))
+
 (define (collapse-locals locs)
   (let lp ((ret '()) (locs locs))
     (if (null? locs)
@@ -209,7 +216,7 @@
                                (number->string (object-address prog) 16)
                                (or (source:file s)
                                    (if s "<current input>" "<unknown port>"))
-                               (source:line s) (source:column s))))
+                               (source:line-for-user s) (source:column s))))
               (number->string (object-address prog) 16))
           (let ((arities (program-arities prog)))
             (if (or (not arities) (null? arities))