jminusminus

Class Context

java.lang.Object

jminusminus.Context

Direct Known Subclasses:

ClassContext, CompilationUnitContext, LocalContext

 class Context
extends Object

A Context encapsulates the environment in which an AST is analyzed. It represents a scope; the scope of a variable is captured by its context. It's the symbol table. Because scopes are lexically nested in Java (and so in j--), the environment can be seen as a stack of contexts, each of which is a mapping from names to their definitions (IDefns). A Context keeps track of it's (most closely) surrounding context, its surrounding class context, and its surrounding compilation unit context, as well as a map of from names to definitions in the level of scope the Context represents. Contexts are created for the compilation unit (a CompilationUnitContext), a class (a ClassContext), each method (a MethodContext), and each block (a LocalContext). If we were to add the for-statement to j--, we would necessarily create a (local) context. From the outside, the structure looks like a tree strung over the AST. But from any location on the AST, that is from any point along a particular branch, it looks like a stack of context objects leading back to the root of the AST, that is, back to the JCompilationUnit object at the root. Part of this structure is built during pre-analysis; pre-analysis reaches only into the type (eg class) declaration for typing the members; pre-analysis does not reach into the method bodies. The rest of it is built during analysis.

Field Summary

Fields

Modifier and Type	Field and Description
protected ClassContext	classContext The surrounding class context.
protected CompilationUnitContext	compilationUnitContext The compilation unit context (for the whole source program or file).
protected Map<String,IDefn>	entries Map of (local variable, formal parameters, type) names to their definitions.
protected Context	surroundingContext The surrounding context (scope).

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Context(Context surrounding, ClassContext classContext, CompilationUnitContext compilationUnitContext) Construct a Context.

Method Summary

Methods

Modifier and Type	Method and Description
void	addEntry(int line, String name, IDefn definition) Add an entry to the symbol table, binding a name to its definition in the current context.
void	addType(int line, Type type) Add the type to the environment.
ClassContext	classContext() Return the surrounding class context.
CompilationUnitContext	compilationUnitContext() Return the surrounding compilation unit context.
Type	definingType() The type that defines this context (used principally for checking acessibility).
IDefn	lookup(String name) Return the definition for a name in the environment.
Type	lookupType(String name) Return the definition for a type name in the environment.
MethodContext	methodContext() Return the closest surrounding method context.
Set<String>	names() The names declared in this context.
Context	surroundingContext() Return the surrounding context (scope) in the stack of contexts.
void	writeToStdOut(PrettyPrinter p) Write the contents of this context to STDOUT.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

surroundingContext

protected Context surroundingContext

The surrounding context (scope).

classContext

protected ClassContext classContext

The surrounding class context.

compilationUnitContext

protected CompilationUnitContext compilationUnitContext

The compilation unit context (for the whole source program or file).

entries

protected Map<String,IDefn> entries

Map of (local variable, formal parameters, type) names to their definitions.

Constructor Detail

Context

protected Context(Context surrounding,
       ClassContext classContext,
       CompilationUnitContext compilationUnitContext)

Construct a Context.

Parameters:

surrounding - the surrounding context (scope).

classContext - the surrounding class context.

compilationUnitContext - the compilation unit context (for the whole source program or file).

Method Detail

addEntry

public void addEntry(int line,
            String name,
            IDefn definition)

Add an entry to the symbol table, binding a name to its definition in the current context.

Parameters:

name - the name being declared.

definition - and its definition.

lookup

public IDefn lookup(String name)

Return the definition for a name in the environment. If it's not found in this context, we look for it in the surrounding context(s).

Parameters:

name - the name whose definition we're looking for.

Returns:

the definition (or null, if not found).

lookupType

public Type lookupType(String name)

Return the definition for a type name in the environment. For now, we look for types only in the CompilationUnitContext.

Parameters:

name - the name of the type whose definition we're looking for.

Returns:

the definition (or null, if not found).

addType

public void addType(int line,
           Type type)

Add the type to the environment.

Parameters:

line - line number of type declaration.

type - the type we are declaring.

definingType

public Type definingType()

The type that defines this context (used principally for checking acessibility).

Returns:

the type that defines this context.

surroundingContext

public Context surroundingContext()

Return the surrounding context (scope) in the stack of contexts.

Returns:

the surrounding context.

classContext

public ClassContext classContext()

Return the surrounding class context.

Returns:

the surrounding class context.

compilationUnitContext

public CompilationUnitContext compilationUnitContext()

Return the surrounding compilation unit context. This is where imported types and other types defined in the compilation unit are declared.

Returns:

the compilation unit context.

methodContext

public MethodContext methodContext()

Return the closest surrounding method context. Return null if we're not within a method.

Returns:

the method context.

names

public Set<String> names()

The names declared in this context.

Returns:

the set of declared names.

writeToStdOut

public void writeToStdOut(PrettyPrinter p)

Write the contents of this context to STDOUT.

Parameters:

p - for pretty printing with indentation.