Semantic Analysis - Crafting a Compiler - page 374

class ThrowsVisitor extends NodeVisitor
/ This extends the class definition of Figure 9.4 /

procedure gather T hrows ( n )

call visit C hildren ( n )

ans ←∅
foreach c ∈ n . getChildren() do ans ← ans ∪ c . throwsSet
n . throwsSet ← ans

end

procedure ( Trying tn )

call tn . catches . accept( this )
call tn . final . accept( this )
currentCatchList ← get

visit

32

C atch L ist ()

call ( tn . catches )

call tn . tryBody . accept( this )
call

update C atch L ist

set C atch L ist ( currentCatchList )

call ( tn . tryBody . throwsSet , tn . catches )

tn . throwsSet ← filter

process C atch

( tryBody . throwsSet , tn . catches )
tn . throwsSet ← tn . throwsSet ∪ tn . catches . throwsSet ∪ tn . final . throwsSet

C atches

end

procedure visit (Catching cn )

33

call gather T hrows ( cn )

end

procedure visit (Throwing tn )

34

call ( tn )

thrownType ← tn . thrownVal . type
tn . throwsSet ← tn . thrownVal . throwsSet ∪ thrownType
if

visit C hildren

assignable ( RuntimeException , thrownType ) or assignable ( Error , thrownType )

then return
else

throwTargets ← get C atch L ist () ∪get D ecl T hrows L ist ()

f ilteredTargets ← filter T hrows ( throwTargets , thrownType )

if size ( throwTargets ) = size ( f ilteredTargets )

then
call error (” Type thrown not f ound in enclosing catch or declared throws list ”)

end

procedure visit (Calling cn )

35

call gather ( cn )

if cn . calledMethod null
then
cn . throwsSet ← cn . throwsSet ∪ cn . calledMethod . declaredThrowsList

T hrows

end

end

Figure 9.28: Throws Analysis Visitors (Part 2)