552 cond expand no match (#554)

* Issue #552 - Error if no match cond-expand clause

* Issue #552 - Document change to cond-expand

CHANGELOG.md

@@ -12,6 +12,7 @@ Bug Fixes
 
 - Added a fix from Yorick Hardy to define `*ai-v4mapped*` to zero on platforms where `AI_V4MAPPED` is undefined.
 - Updated `sqrt` to properly handle complex results given non-complex input. EG: `(sqrt -1) ==> 1i`. And updated the parser to properly handle `+i` and `-i`. Thanks to Christopher Hebert for the bug reports!
+- Updated `cond-expand` to raise an error if no clauses match, instead of returning `#t`.
 
 ## 0.36.0 - February 14, 2024
 

scheme/base.sld

@@ -407,7 +407,7 @@
                   (else (error "cond-expand: bad feature" x)))
                 (memq x (features))))
           (let expand ((ls (cdr expr)))
-            (cond ((null? ls))  ; (error "cond-expand: no expansions" expr)
+            (cond ((null? ls)  (error "cond-expand: no expansions" expr))
                   ((not (pair? (car ls))) (error "cond-expand: bad clause" (car ls)))
                   ((eq? 'else (caar ls)) ;(identifier->symbol (caar ls)))
                    (if (pair? (cdr ls))

tests/base.scm

@@ -54,6 +54,7 @@
       (test "o" (read-line p))
     )
   )
+  (else #f)
 )
 
 (test-group