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package com.craftinginterpreters.lox;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Stack;
class Resolver implements Expr.Visitor<Void>, Stmt.Visitor<Void> {
private final Interpreter interpreter;
private final Stack<Map<String, Boolean>> scopes = new Stack<>();
private FunctionType currentFunction = FunctionType.NONE;
Resolver(Interpreter interpreter) {
this.interpreter = interpreter;
}
private enum FunctionType {
NONE, FUNCTION
}
public void resolve(List<Stmt> statements) {
for (Stmt statement : statements) {
resolve(statement);
}
}
@Override
public Void visitBlockStmt(Stmt.Block stmt) {
beginScope();
resolve(stmt.statements);
endScope();
return null;
}
@Override
public Void visitClassStmt(Stmt.Class stmt) {
declare(stmt.name);
define(stmt.name);
return null;
}
@Override
public Void visitExpressionStmt(Stmt.Expression stmt) {
resolve(stmt.expression);
return null;
}
@Override
public Void visitFunctionStmt(Stmt.Function stmt) {
declare(stmt.name);
define(stmt.name);
resolveFunction(stmt, FunctionType.FUNCTION);
return null;
}
@Override
public Void visitIfStmt(Stmt.If stmt) {
resolve(stmt.condition);
resolve(stmt.thenBranch);
if (stmt.elseBranch != null)
resolve(stmt.elseBranch);
return null;
}
@Override
public Void visitPrintStmt(Stmt.Print stmt) {
resolve(stmt.expression);
return null;
}
@Override
public Void visitReturnStmt(Stmt.Return stmt) {
if (currentFunction == FunctionType.NONE) {
Lox.error(stmt.keyword, "Can't return from top-level code.");
}
if (stmt.value != null) {
resolve(stmt.value);
}
return null;
}
@Override
public Void visitVarStmt(Stmt.Var stmt) {
declare(stmt.name);
if (stmt.initializer != null) {
resolve(stmt.initializer);
}
define(stmt.name);
return null;
}
@Override
public Void visitWhileStmt(Stmt.While stmt) {
resolve(stmt.condition);
resolve(stmt.body);
return null;
}
@Override
public Void visitAssignExpr(Expr.Assign expr) {
resolve(expr.value);
resolveLocal(expr, expr.name);
return null;
}
@Override
public Void visitBinaryExpr(Expr.Binary expr) {
resolve(expr.left);
resolve(expr.right);
return null;
}
@Override
public Void visitCallExpr(Expr.Call expr) {
resolve(expr.callee);
for (Expr argument : expr.arguments) {
resolve(argument);
}
return null;
}
@Override
public Void visitGetExpr(Expr.Get expr) {
resolve(expr.object);
return null;
}
@Override
public Void visitGroupingExpr(Expr.Grouping expr) {
resolve(expr.expression);
return null;
}
@Override
public Void visitLiteralExpr(Expr.Literal expr) {
return null;
}
@Override
public Void visitSetExpr(Expr.Set expr) {
resolve(expr.value);
resolve(expr.object);
return null;
}
@Override
public Void visitLogicalExpr(Expr.Logical expr) {
resolve(expr.left);
resolve(expr.right);
return null;
}
@Override
public Void visitUnaryExpr(Expr.Unary expr) {
resolve(expr.right);
return null;
}
@Override
public Void visitVariableExpr(Expr.Variable expr) {
if (!scopes.isEmpty() && scopes.peek().get(expr.name.lexeme) == Boolean.FALSE) {
Lox.error(expr.name, "Can't read local variable in its own initializer.");
}
resolveLocal(expr, expr.name);
return null;
}
private void resolve(Stmt stmt) {
stmt.accept(this);
}
private void resolve(Expr expr) {
expr.accept(this);
}
private void resolveFunction(Stmt.Function function, FunctionType type) {
FunctionType enclosingFunction = currentFunction;
currentFunction = type;
beginScope();
for (Token param : function.params) {
declare(param);
define(param);
}
resolve(function.body);
endScope();
currentFunction = enclosingFunction;
}
private void beginScope() {
scopes.push(new HashMap<String, Boolean>());
}
private void endScope() {
scopes.pop();
}
private void declare(Token name) {
if (scopes.isEmpty())
return;
Map<String, Boolean> scope = scopes.peek();
if (scope.containsKey(name.lexeme)) {
Lox.error(name, "Already variable with this name in this scope.");
}
scope.put(name.lexeme, false);
}
private void define(Token name) {
if (scopes.isEmpty())
return;
scopes.peek().put(name.lexeme, true);
}
private void resolveLocal(Expr expr, Token name) {
for (int i = scopes.size() - 1; i >= 0; i--) {
if (scopes.get(i).containsKey(name.lexeme)) {
interpreter.resolve(expr, scopes.size() - 1 - i);
return;
}
}
}
}
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