Semantic Analysis - Crafting a Compiler - page 365

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 9.1 /

procedure (Switching sn )

call sn . control . accept( this )
if sn . control . type errorType and not

visit

28

assignable ( int , sn . control . type )

then
call error (” Illegal type f or control expression ”)

call set S witch T ype ( errorType )

else call set ( sn . control . type )

call sn . cases . accept( this )
labelList ← sort

S witch T ype

( gather L abels ( sn . cases ))

call check F or D uplicates ( labelList )

if count D efaults ( sn . cases ) > 1

then call error (” More than one de f ault case label ”)

end

procedure visit (CaseItem cn )

call visit C hildren ( cn )

end

procedure visit ( LabelList lln )

call visit C hildren ( lln )

lln . caseLabel ← null

if lln . caseExp . type errorType
then
if not assignable ( get S witch T ype () , lln . caseExp . type )

then call error (” Invalid case label type ”)

else

constExprVisitor ← new ConstExprVisitor()

call lln . caseExp . accept( constExprVisitor )
labelValue ← lln . caseExp . exprValue
if labelValue = null

then call error (” Case label must be a constant expression ”)

end

end

Figure 9.21: Semantic Analysis Visitors (Part 2)