Symbol Tables and Declaration Processing - Crafting a Compiler - page 304

/ Visitor code for Marker 12 on page 302 /

procedure visit (VariableListDeclaring vld )

typeVisitor ← new TypeVisitor()

20

call vld . typeName . accept( typeVisitor )

21

foreach id ∈ vld . idList do

22

if currentSymbolTable . declaredLocally( id . name )
then
call

23

error (” This variable is already declared :” , id . name )

id . type ← errorType
id . attributesRe f ← null

else

id . type ← vld . typeName . type
attr . kind ← variableAttributes
attr . variableType ← id . type
id . attributesRe f ← attr
call currentSymbolTable . enterSymbol( id . name , attr )

24

end

Figure 8.13: visit method in TopDeclVisitor for VariableListDeclaring.

8.6.2 Handling Type Names

The method inFigure 8.14 defines the actions performedby the TypeVisitor

when it visits an Identifier. It begins by looking for the identifier in the symbol
table using

visit

at Marker 25 . If the attributes returned indicate
that id does name a type, then a reference to the type descriptor for that type
is assigned at Marker 26 to type , which stores the result of this retrieval pro-
cess. If the Identifier does not name a type, an error message is produced at
Marker 27 . type is set to refer to a special type descriptor, errorType , indicating
the error. Use of errorType to streamline error reporting will be discussed in

retrieve S ymbol

/ Visitor code for Marker 16 on page 302 /

procedure visit ( Identifier id )

attr ← currentSymbolTable . retrieveSymbol( id . name )
if attr null and attr . kind = typeAttributes
then

25

id . type ← attr . thisType
id . attributesRe f ← attr

26

else

call error (” This identi f ier is not a type name :” , id . name )

27

id . type ← errorType
id . attributesRe f ← null

end

Figure 8.14: visit method in TypeVisitor for Identifier.