Semantic Analysis - Crafting a Compiler - page 371

class NodeVisitor
procedure

( n )
foreach c ∈ n . getChildren() do call c . accept( this )

visit C hildren

end

end

class SemanticsVisitor extends NodeVisitor
/ This extends the class definition of Figure 9.21 / 29

procedure visit ( Trying tn )

call visit C hildren ( tn )

end

procedure visit (Catching cn )

30

if not assignable ( Throwable , cn . catchIdDecl . type )

then
call (” Illegal type f or catch identi f ier ”)

cn . catchIdDecl . type ← errorType

error

else

if subsumes L ater C atches ( cn . catchIdDecl . type , cn . more )

then call error (” This catch hides later catches ”)

call ()

attr . kind ← variableAttributes
attr . variableType ← cn . catchIdDecl . type . getTypeDescriptor()
call currentSymbolTable . enterSymbol( cn . catchIdDecl . ident . name , attr )
call cn . catchBody . accept( this )
call

open S cope

()
call cn . more . accept( this )

close S cope

end

procedure visit (Throwing tn )

31

call ( tn )

if tn . thrownVal . type errorType and not

visit C hildren

assignable ( Throwable , tn . thrownVal . type )

then call error (” Illegal type f or throw ”)

end

end

Figure 9.26: Semantic Analysis Visitors (Part 3)