[dcl.attr.contract] Clarify evaluation of non-checked contracts

Author: jensmaurer

source/declarations.tex

@@ -4563,6 +4563,8 @@
 A translation may be performed
 with one of the following \defnx{build levels}{build level}:
 \term{off}, \term{default}, or \term{audit}.
+A translation with build level set to \term{off}
+performs no checking for any contract.
 A translation with build level set to \term{default}
 performs checking for \tcode{default} contracts.
 A translation with build level set to \term{audit}
@@ -4577,11 +4579,13 @@
 the build level of a translation unit.
 
 \pnum
-It is unspecified whether a contract
-that would not be checked under the current build level is evaluated.
-If it would evaluate to \tcode{false}, the behavior is undefined.
 During constant expression evaluation\iref{expr.const},
-contract evaluation is performed only for those contracts that are checked.
+only predicates of checked contracts are evaluated.
+In other contexts,
+it is unspecified whether the predicate for a contract
+that is not checked under the current build level is evaluated;
+if the predicate of such a contract
+would evaluate to \tcode{false}, the behavior is undefined.
 
 \pnum
 The \defn{violation handler} of a program is a function of type