scope and promote the way C does

A `while' or `switch' body is a block with no `do' around it, and its
declarations landed in the enclosing frame. Two operands of one narrow
type skipped the conversions, so `(+ c c)' answered `char'.

tests/sex-programs/wildcards.sex

@@ -6,8 +6,10 @@
         "arrays: 30"
         "loop: 0 1 2"
         "shadowed: 9 then 42"
+        "still an int: 200"
         "partial: 1 2.5"
         "joined: 43.5 84 49 1"
+        "promoted: 200 60000 3705032704"
         "from elements: 4 9 0")
 (return 0)
 
@@ -55,11 +57,24 @@
        (printf " %d" i))
   (printf "\n")
 
-  ;; a block's declarations end with it
+  ;; a block's declarations end with it, and so do the declarations of
+  ;; everything else C brackets -- a `while' body is a block with no
+  ;; `do' written around it
   (do (var n _ 9)
       (printf "shadowed: %d then " n))
   (printf "%d\n" n)
 
+  (var wide int 200)
+  (while false (var wide char 1) (printf "%d" wide))
+  (if false (do (var wide char 1) (printf "%d" wide)))
+  ;; a statement before the declaration: a label may not be followed by
+  ;; one until C23
+  (switch a (case 1 (printf "") (var wide char 1) (printf "%d" wide) (break)))
+  ;; a copy, not a sum: an arithmetic result would be promoted to `int'
+  ;; whatever leaked, and say nothing
+  (var copy _ wide)
+  (printf "still an int: %d\n" copy)
+
   ;; a wildcard inside a written type: only it is solved
   (var pp2 (* _) (& p))
   (printf "partial: %d %g\n" (-> pp2 x) (-> pp2 y))
@@ -74,6 +89,17 @@
   (var single _ (+ g g))
   (printf "joined: %g %d %ld %g\n" mixed same wider single)
 
+  ;; ...including the promotions, which two operands of one narrow type
+  ;; are exactly where they show: `char' + `char' is an `int'
+  (var c1 char 100)
+  (var c2 char 100)
+  (var h1 short 30000)
+  (var narrow _ (+ c1 c2))
+  (var narrower _ (+ h1 h1))
+  (var kept (unsigned int) 4000000000)
+  (var unpromoted _ (+ kept kept))
+  (printf "promoted: %d %d %u\n" narrow narrower unpromoted)
+
   ;; a brace initializer has no type of its own, but its elements solve
   ;; the hole in the array type around it -- and the length stays as
   ;; written, whether or not every slot is initialized