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added scope rules, removed TODO

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Robert Griesemer 2008-08-21 11:00:26 -07:00
parent bb05942638
commit c2c49bec77
1 changed files with 26 additions and 6 deletions
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32
doc/go_lang.txt
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@ -1013,19 +1013,39 @@ Literals
Literal = char_lit | string_lit | int_lit | float_lit | FunctionLit | "nil" .
Declarations
Declaration and scope rules
----
A declaration associates a name with a language entity such as a constant, type,
variable, or function.
Every identifier in a program must be declared; some identifiers, such as "int"
and "true", are predeclared. A declaration associates an identifier
with a language entity (package, constant, type, variable, function, method,
or label) and may specify properties of that entity such as its type.
Declaration = [ "export" ] ( ConstDecl | TypeDecl | VarDecl | FunctionDecl ) .
The ``scope'' of a language entity named 'x' extends textually from the point
immediately after the identifier 'x' in the declaration to the end of the
surrounding block (package, function, struct, or interface), excluding any
nested scopes that redeclare 'x'. The entity is said to be local to its scope.
Declarations in the package scope are ``global'' declarations.
The following scope rules apply:
1. No identifier may be declared twice in a single scope.
2. A language entity may only be referred to within its scope.
3. Field and method identifiers may be used only to select elements
from the corresponding types. In effect, the field selector operator
'.' temporarily re-opens the scope of such identifiers (see Expressions).
4. Forward declaration: A type of the form "*T" may be mentioned at a point
where "T" is not yet declared. The declaration of "T" must follow in the
same package and "T" must be visible at the end of the block containing "*T".
Global declarations optionally may be marked for export with the reserved word
"export". Local declarations can never be exported.
All identifiers (and only those identifiers) declared in exported declarations
are made visible to clients of this package, that is other packages that import
are made visible to clients of this package, that is, other packages that import
this package.
If the declaration defines a type, the type structure is exported as well. In
particular, if the declaration defines a new "struct" or "interface" type,
all structure fields and all structure and interface methods are exported also.
@ -1037,8 +1057,8 @@ Note that at the moment the old-style export via ExportDecl is still supported.
TODO: Eventually we need to be able to restrict visibility of fields and methods.
(gri) The default should be no struct fields and methods are automatically exported.
TODO: specify range of visibility, scope rules.
Export should be identifier-based: an identifier is either exported or not, and thus
visible or not in importing package.
[OLD
Declaration = ConstDecl | TypeDecl | VarDecl | FunctionDecl | ExportDecl .