scopes
parent
eca4492492
commit
36e56567db
@ -0,0 +1,209 @@
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package lox;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import java.util.Stack;
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class Resolver implements Expr.Visitor<Void>, Stmt.Visitor<Void> {
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private final Interpreter interpreter;
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private final Stack<Map<String, Boolean>> scopes = new Stack<>();
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private FunctionType currentFunction = FunctionType.NONE;
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Resolver(Interpreter interpreter) {
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this.interpreter = interpreter;
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}
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private enum FunctionType {
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NONE,
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FUNCTION
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}
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void resolve(List<Stmt> statements) {
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for (Stmt statement : statements) {
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resolve(statement);
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}
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}
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private void resolve(Stmt stmt) {
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stmt.accept(this);
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}
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private void resolve(Expr expr) {
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expr.accept(this);
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}
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private void resolveLocal(Expr expr, Token name) {
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for (int i = scopes.size() - 1; i >= 0; i--) {
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if (scopes.get(i).containsKey(name.lexeme)) {
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interpreter.resolve(expr, scopes.size() - i - 1);
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return;
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}
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}
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}
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private void resolveFunction(Stmt.Function function, FunctionType type) {
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FunctionType enclosingFunction = currentFunction;
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currentFunction = type;
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beginScope();
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for (Token param : function.params) {
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declare(param);
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define(param);
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}
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resolve(function.body);
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endScope();
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currentFunction = enclosingFunction;
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}
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private void beginScope() {
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scopes.push(new HashMap<>());
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}
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private void endScope() {
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scopes.pop();
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}
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private void declare(Token name) {
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if (scopes.isEmpty()) {
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return;
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}
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Map<String, Boolean> scope = scopes.peek();
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if (scope.containsKey(name.lexeme)) {
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Lox.error(name, "Already a variable with this name in this scope.");
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}
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scope.put(name.lexeme, false);
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}
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private void define(Token name) {
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if (scopes.isEmpty()) {
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return;
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}
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scopes.peek().put(name.lexeme, true);
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}
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@Override
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public Void visitBlockStmt(Stmt.Block stmt) {
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beginScope();
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resolve(stmt);
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endScope();
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return null;
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}
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@Override
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public Void visitExpressionStmt(Stmt.Expression stmt) {
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resolve(stmt.expression);
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return null;
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}
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@Override
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public Void visitVarStmt(Stmt.Var stmt) {
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declare(stmt.name);
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if (stmt.initializer != null) {
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resolve(stmt.initializer);
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}
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define(stmt.name);
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return null;
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}
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@Override
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public Void visitWhileStmt(Stmt.While stmt) {
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resolve(stmt.condition);
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resolve(stmt.body);
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return null;
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}
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@Override
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public Void visitVariableExpr(Expr.Variable expr) {
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if (!scopes.isEmpty() && scopes.peek().get(expr.name.lexeme) == Boolean.FALSE) {
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Lox.error(expr.name, "Can't read local variable in its own initializer");
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}
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resolveLocal(expr, expr.name);
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return null;
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}
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@Override
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public Void visitAssignExpr(Expr.Assign expr) {
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resolve(expr.value);
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resolveLocal(expr, expr.name);
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return null;
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}
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@Override
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public Void visitBinaryExpr(Expr.Binary expr) {
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resolve(expr.left);
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resolve(expr.right);
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return null;
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}
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@Override
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public Void visitCallExpr(Expr.Call expr) {
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resolve(expr.callee);
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for (Expr argument : expr.arguments) {
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resolve(argument);
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}
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return null;
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}
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@Override
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public Void visitGroupingExpr(Expr.Grouping expr) {
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resolve(expr.expression);
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return null;
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}
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@Override
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public Void visitLiteralExpr(Expr.Literal expr) {
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return null;
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}
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@Override
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public Void visitLogicalExpr(Expr.Logical expr) {
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resolve(expr.left);
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resolve(expr.right);
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return null;
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}
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@Override
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public Void visitUnaryExpr(Expr.Unary expr) {
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resolve(expr.right);
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return null;
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}
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@Override
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public Void visitFunctionStmt(Stmt.Function stmt) {
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declare(stmt.name);
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define(stmt.name);
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resolveFunction(stmt, FunctionType.FUNCTION);
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return null;
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}
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@Override
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public Void visitIfStmt(Stmt.If stmt) {
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resolve(stmt.condition);
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resolve(stmt.thenBranch);
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if (stmt.elseBranch != null) {
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resolve(stmt.elseBranch);
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}
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return null;
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}
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@Override
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public Void visitPrintStmt(Stmt.Print stmt) {
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resolve(stmt.expression);
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return null;
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}
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@Override
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public Void visitReturnStmt(Stmt.Return stmt) {
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if (currentFunction == FunctionType.NONE) {
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Lox.error(stmt.keyword, "Can't return from top-level code.");
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}
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if (stmt.value != null) {
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resolve(stmt.value);
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}
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return null;
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}
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}
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