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13.14 Freezing Rules

1
This clause defines a place in the program text where each declared entity becomes “frozen.” A use of an entity, such as a reference to it by name, or (for a type) an expression of the type, causes freezing of the entity in some contexts, as described below. The Legality Rules forbid certain kinds of uses of an entity in the region of text where it is frozen. 
2
The freezing of an entity occurs at one or more places (freezing points) in the program text where the representation for the entity has to be fully determined. Each entity is frozen from its first freezing point to the end of the program text (given the ordering of compilation units defined in 10.1.4). 
3/1
The end of a declarative_part, protected_body, or a declaration of a library package or generic library package, causes freezing of each entity declared within it, except for incomplete types. A noninstance body other than a renames-as-body causes freezing of each entity declared before it within the same declarative_part.
4/1
A construct that (explicitly or implicitly) references an entity can cause the freezing of the entity, as defined by subsequent paragraphs. At the place where a construct causes freezing, each name, expression, implicit_dereference, or range within the construct causes freezing: 
5
6
7
7.1/2
8/1
A static expression causes freezing where it occurs. An object name or nonstatic expression causes freezing where it occurs, unless the name or expression is part of a default_expression, a default_name, or a per-object expression of a component's constraint, in which case, the freezing occurs later as part of another construct.
8.1/1
  An implicit call freezes the same entities that would be frozen by an explicit call. This is true even if the implicit call is removed via implementation permissions.
8.2/1
  If an expression is implicitly converted to a type or subtype T, then at the place where the expression causes freezing, T is frozen.
9
The following rules define which entities are frozen at the place where a construct causes freezing: 
10
11
11.1/1
12
13
14
15
15.1/2

Legality Rules

16
The explicit declaration of a primitive subprogram of a tagged type shall occur before the type is frozen (see 3.9.2). 
17
A type shall be completely defined before it is frozen (see 3.11.1 and 7.3).
18
The completion of a deferred constant declaration shall occur before the constant is frozen (see 7.4).
19/1
 An operational or representation item that directly specifies an aspect of an entity shall appear before the entity is frozen (see 13.1).

Dynamic Semantics

20/2
 The tag (see 3.9) of a tagged type T is created at the point where T is frozen.

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