Semantic Analysis - Crafting a Compiler - page 379

function more S pecific ( de f 1 , de f 2) returns Boolean

38

if bindable ( de f 1 . classDe f inedIn , de f 2 . classDe f inedIn )

then
arg 1 ← de f 1 . argTypes

arg 2 ← de f 2 . argTypes

while arg 1 null do

if bindable ( head ( arg 1) ,head ( arg 2))

then
arg 1

← tail ( arg 1)

( arg 2)
else return false
return ( true )
else return false

arg 2 ← tail

end

function filter D efs ( methodDe f Set ) returns Boolean

39

changes ← true
while changes do
changes ← false
foreach de f 1 ∈ methodDe f Set do

foreach de f 2 ∈ methodDe f Set do

if de f 1

de f 2 and

more S pecific ( de f 1 , de f 2)

then
methodDe f Set ← methodDe f Set −{ de f 1 }

changes ← true
return methodDe f Set

end

Figure 9.33: Utility Semantic Methods for Method Calls (Part 2)

return type. The method extracts a list of parameter types from the

method signature. This list is comparedwith the list of actual parameter types.
But what exactly defines a match between formal and actual parameters?
First, both argument lists must have the same length—this is easy to check.
Next, each actual parameter must be ”bindable” to its corresponding formal
parameter.
Bindable means that it is legal to use an actual parameter whenever the
corresponding formal parameter is referenced. In Java, bindable is almost
the same as assignable. When interfaces are considered, a class object may
sometimes be bound even if it may not be directly assigned.
Now checking the feasibility of using a particular method definition in a
call is straightforward (we check that the number of parameters is correct and
that each parameter is bindable). This is detailed in Figure 9.32, Marker 37 ,
which defines the method

get A rgs

applicable ( f ormalParms , actualParms ). If applicable