Type Checking - Introduction to Compiler Construction in a Java World - page 133

FIGURE 4.3 The inheritance tree for contexts.
An IDefn is the interface type for symbol table definitions, which has two implementa-
tions:
1. A TypeNameDefn , which defines a type name. An IDefn of this sort encapsulates the
Type that it denotes.
2. A LocalVariableDefn defines a local variable and encapsulates the name, its Type ,
and an offset in the current run-time stack frame. (We discuss stack frame offsets in
Section 4.5.2.)
4.3.2 Finding Method and Field Names in Type Objects
As we discussed in Section 4.2.3, the types defined by classes are represented in the same
way as they are in the Java library, so that we may consistently manipulate types that we
define and types that we import.
Class member (field and method in j--) names are not declared in a ClassContext ,
but in the Types that they declare. We rely on the encapsulated Class object to store the
interface information, and we rely on Java reflection to query a type for information about
its members.
For example, Type supports a method fieldFor() that, when given a name, returns
a Field with the given name that is defined for that type. It delegates the finding of this
field to a search of the underlying Class object and can be seen from the code that defines
fieldFor() :
publicFieldfieldFor(Stringname){
Class<?>cls=classRep;
while(cls!=null){
java.lang.reflect.Field[]fields=
cls.getDeclaredFields();
for(java.lang.reflect.Fieldfield:fields){
if(field.getName().equals(name)){
returnnewField(field);
}
}
cls=cls.getSuperclass();
}
returnnull;
}
This code first looks for the named field in the Class object for the Type being defined. If it
does not find it there, it looks in the Class object for the Type 's super type, and so on until
either the field is found or we come to the base of the inheritance tree, in which case null is
returned to indicate that no such field was found. If we find the java.lang.reflect.Field ,