ASTFun.java

public class ASTFun implements ASTNode {
    private final String param;
    private final ASTType paramType;
    private ASTNode body;
    
    public ASTFun(String param, ASTType paramType, ASTNode body) {
        this.param = param;
        this.paramType = paramType;
        this.body = body;
    }

    public void setBody(ASTNode b) {
	    body = b;
    }
    
    @Override
    public IValue eval(Environment<IValue> e) throws InterpreterError {
        return new VClosure(param, body, e);
    }

    @Override
    public ASTType typecheck(Environment<ASTType> e) throws TypeCheckError, InterpreterError {
        if (paramType == null) {
            throw new TypeCheckError("fn: missing type annotation for parameter '" + param + "'");
        }
        
        ASTType resolvedParamType = ASTTypeDef.unfold(paramType, e);
        
        Environment<ASTType> newEnv = e.beginScope();
        newEnv.assoc(param, resolvedParamType);
        
        ASTType bodyType = body.typecheck(newEnv);

        if (bodyType instanceof ASTTAddr addrType) {
            if (addrType.getDepth() > e.getDepth()) {
                throw new TypeCheckError("Illegal escape of stack address: pointer to a local variable outlives the function scope!");
            }
        }

        newEnv.endScope();
        return new ASTTArrow(resolvedParamType, bodyType);
    }

}