Section WT_CONTEXT.
Variable cenv: composite_env.
Variable tenv: typenv.
Variable a a': expr.
Hypothesis SAMETY: typeof a' = typeof a.

Lemma wt_context:
forall from to C,
context from to C ->
wt_expr_kind cenv tenv to (C a) ->
wt_expr_kind cenv tenv from a' ->
wt_expr_kind cenv tenv to (C a')
with wt_contextlist:
forall from C,
contextlist from C ->
wt_exprlist cenv tenv (C a) ->
wt_expr_kind cenv tenv from a' ->
wt_exprlist cenv tenv (C a').