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<H1> 10.1.6 Environment-Level Visibility Rules</H1>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal"> [The normal visibility rules do not apply within
a <FONT FACE="Arial, Helvetica">parent_unit_name</FONT> or a <FONT FACE="Arial, Helvetica">context_clause</FONT>,
nor within a <FONT FACE="Arial, Helvetica">pragma</FONT> that appears
at the place of a compilation unit. The special visibility rules for
those contexts are given here.] </DIV>
<H4 ALIGN=CENTER>Static Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>2</FONT></DIV>
<DIV Class="Normal"> <A NAME="I3943"></A><A NAME="I3944"></A><A NAME="I3945"></A><A NAME="I3946"></A>Within
the <FONT FACE="Arial, Helvetica">parent_unit_name</FONT> at the beginning
of a <FONT FACE="Arial, Helvetica">library_item</FONT>, and within a
<FONT FACE="Arial, Helvetica">with_clause</FONT>, the only declarations
that are visible are those that are <FONT FACE="Arial, Helvetica">library_item</FONT>s
of the environment, and the only declarations that are directly visible
are those that are root <FONT FACE="Arial, Helvetica">library_item</FONT>s
of the environment. <A NAME="I3947"></A>Notwithstanding the rules of
<A HREF="AA-4-1-3.html">4.1.3</A>, an expanded name in a <FONT FACE="Arial, Helvetica">with_clause</FONT>
may consist of a <FONT FACE="Arial, Helvetica">prefix</FONT> that denotes
a generic package and a <FONT FACE="Arial, Helvetica">selector_name</FONT>
that denotes a child of that generic package. [(The child is necessarily
a generic unit; see <A HREF="AA-10-1-1.html">10.1.1</A>.)]</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>2.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Ramification: </B>In ``<B>package</B>
P.Q.R <B>is</B> ... <B>end</B> P.Q.R;'', this rule requires P to be a
root library unit, and Q to be a library unit (because those are the
things that are directly visible and visible). Note that visibility does
not apply between the ``<B>end</B>'' and the ``;''.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>2.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>Physically nested declarations
are not visible at these places. </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>2.c</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Reason: </B>Although Standard
is visible at these places, it is impossible to name it, since it is
not directly visible, and it has no parent. </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>2.d</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Reason: </B>The ``notwithstanding''
part allows ``<B>with</B> A.B;'' where A is a generic library package
and B is one of its (generic) children. This is necessary because it
is not normally legal to use an expanded name to reach inside a generic
package.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3</FONT></DIV>
<DIV Class="Normal"> <A NAME="I3948"></A><A NAME="I3949"></A><A NAME="I3950"></A><A NAME="I3951"></A>Within
a <FONT FACE="Arial, Helvetica">use_clause</FONT> or <FONT FACE="Arial, Helvetica">pragma</FONT>
that is within a <FONT FACE="Arial, Helvetica">context_clause</FONT>,
each <FONT FACE="Arial, Helvetica">library_item</FONT> mentioned in a
previous <FONT FACE="Arial, Helvetica">with_clause</FONT> of the same
<FONT FACE="Arial, Helvetica">context_clause</FONT> is visible, and each
root <FONT FACE="Arial, Helvetica">library_item</FONT> so mentioned is
directly visible. In addition, within such a <FONT FACE="Arial, Helvetica">use_clause</FONT>,
if a given declaration is visible or directly visible, each declaration
that occurs immediately within the given declaration's visible part is
also visible. No other declarations are visible or directly visible.
</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Discussion: </B>Note the word
``same''. For example, if a <FONT FACE="Arial, Helvetica">with_clause</FONT>
on a declaration mentions X, this does not make X visible in <FONT FACE="Arial, Helvetica">use_clause</FONT>s
and <FONT FACE="Arial, Helvetica">pragma</FONT>s that are on the body.
The reason for this rule is the one-pass <FONT FACE="Arial, Helvetica">context_clause</FONT>s
Language Design Principle.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>Note that the second part of the
rule does not mention <FONT FACE="Arial, Helvetica">pragma</FONT>s. </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>4</FONT></DIV>
<DIV Class="Normal"> <A NAME="I3952"></A><A NAME="I3953"></A>Within
the <FONT FACE="Arial, Helvetica">parent_unit_name</FONT> of a subunit,
<FONT FACE="Arial, Helvetica">library_item</FONT>s are visible as they
are in the <FONT FACE="Arial, Helvetica">parent_unit_name</FONT> of a
<FONT FACE="Arial, Helvetica">library_item</FONT>; in addition, the declaration
corresponding to each <FONT FACE="Arial, Helvetica">body_stub</FONT>
in the environment is also visible. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>4.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Ramification: </B>For a subprogram
without a separate <FONT FACE="Arial, Helvetica">subprogram_declaration</FONT>,
the <FONT FACE="Arial, Helvetica">body_stub</FONT> itself is the declaration.
</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>5</FONT></DIV>
<DIV Class="Normal"> <A NAME="I3954"></A><A NAME="I3955"></A>Within
a <FONT FACE="Arial, Helvetica">pragma</FONT> that appears at the place
of a compilation unit, the immediately preceding <FONT FACE="Arial, Helvetica">library_item</FONT>
and each of its ancestors is visible. The ancestor root <FONT FACE="Arial, Helvetica">library_item</FONT>
is directly visible.</DIV>
<H4 ALIGN=CENTER>Wording Changes from Ada 83</H4>
<DIV Class="Paranum"><FONT SIZE=-2>5.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>The special visibility rules that
apply within a <FONT FACE="Arial, Helvetica">parent_unit_name</FONT>
or a <FONT FACE="Arial, Helvetica">context_clause</FONT>, and within
a <FONT FACE="Arial, Helvetica">pragma</FONT> that appears at the place
of a <FONT FACE="Arial, Helvetica">compilation_unit</FONT> are clarified.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>5.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>Note that a <FONT FACE="Arial, Helvetica">context_clause</FONT>
is not part of any declarative region.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>5.c</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>We considered making the visibility
rules within <FONT FACE="Arial, Helvetica">parent_unit_name</FONT>s and
<FONT FACE="Arial, Helvetica">context_clause</FONT>s follow from the
context of compilation. However, this attempt failed for various reasons.
For example, it would require <FONT FACE="Arial, Helvetica">use_clause</FONT>s
in <FONT FACE="Arial, Helvetica">context_clause</FONT>s to be within
the declarative region of Standard, which sounds suspiciously like a
kludge. And we would still need a special rule to prevent seeing things
(in our own <FONT FACE="Arial, Helvetica">context_clause</FONT>) that
were with-ed by our parent, etc. </FONT></DIV>
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