tvl-depot/src/libexpr/nixexpr.cc
Shea Levy 136f2f7046 Add the ExprBuiltin Expr type to the AST
Certain desugaring schemes may require the parser to use some builtin
function to do some of the work (e.g. currently `throw` is used to
lazily cause an error if a `<>`-style path is not in the search path)
Unfortunately, these names are not reserved keywords, so an expression
that uses such a syntactic sugar will not see the expected behavior
(see tests/lang/eval-okay-redefine-builtin.nix for an example).

This adds the ExprBuiltin AST type, which when evaluated uses the value
from the rootmost variable scope (which of course is initialized
internally and can't shadow any of the builtins).

Signed-off-by: Shea Levy <shea@shealevy.com>
2013-12-31 17:45:47 +00:00

369 lines
7.6 KiB
C++

#include "nixexpr.hh"
#include "derivations.hh"
#include "util.hh"
#include <cstdlib>
namespace nix {
/* Displaying abstract syntax trees. */
std::ostream & operator << (std::ostream & str, Expr & e)
{
e.show(str);
return str;
}
void Expr::show(std::ostream & str)
{
abort();
}
void ExprInt::show(std::ostream & str)
{
str << n;
}
void ExprString::show(std::ostream & str)
{
str << "\"" << s << "\""; // !!! escaping
}
void ExprPath::show(std::ostream & str)
{
str << s;
}
void ExprVar::show(std::ostream & str)
{
str << name;
}
void ExprSelect::show(std::ostream & str)
{
str << "(" << *e << ")." << showAttrPath(attrPath);
if (def) str << " or " << *def;
}
void ExprOpHasAttr::show(std::ostream & str)
{
str << "(" << *e << ") ? " << showAttrPath(attrPath);
}
void ExprAttrs::show(std::ostream & str)
{
if (recursive) str << "rec ";
str << "{ ";
foreach (AttrDefs::iterator, i, attrs)
if (i->second.inherited)
str << "inherit " << i->first << " " << "; ";
else
str << i->first << " = " << *i->second.e << "; ";
str << "}";
}
void ExprList::show(std::ostream & str)
{
str << "[ ";
foreach (vector<Expr *>::iterator, i, elems)
str << "(" << **i << ") ";
str << "]";
}
void ExprLambda::show(std::ostream & str)
{
str << "(";
if (matchAttrs) {
str << "{ ";
bool first = true;
foreach (Formals::Formals_::iterator, i, formals->formals) {
if (first) first = false; else str << ", ";
str << i->name;
if (i->def) str << " ? " << *i->def;
}
str << " }";
if (!arg.empty()) str << " @ ";
}
if (!arg.empty()) str << arg;
str << ": " << *body << ")";
}
void ExprLet::show(std::ostream & str)
{
str << "let ";
foreach (ExprAttrs::AttrDefs::iterator, i, attrs->attrs)
if (i->second.inherited)
str << "inherit " << i->first << "; ";
else
str << i->first << " = " << *i->second.e << "; ";
str << "in " << *body;
}
void ExprWith::show(std::ostream & str)
{
str << "with " << *attrs << "; " << *body;
}
void ExprIf::show(std::ostream & str)
{
str << "if " << *cond << " then " << *then << " else " << *else_;
}
void ExprAssert::show(std::ostream & str)
{
str << "assert " << *cond << "; " << *body;
}
void ExprOpNot::show(std::ostream & str)
{
str << "! " << *e;
}
void ExprBuiltin::show(std::ostream & str)
{
str << "builtins." << name;
}
void ExprConcatStrings::show(std::ostream & str)
{
bool first = true;
foreach (vector<Expr *>::iterator, i, *es) {
if (first) first = false; else str << " + ";
str << **i;
}
}
void ExprPos::show(std::ostream & str)
{
str << "__curPos";
}
std::ostream & operator << (std::ostream & str, const Pos & pos)
{
if (!pos.line)
str << "undefined position";
else
str << (format("`%1%:%2%:%3%'") % pos.file % pos.line % pos.column).str();
return str;
}
string showAttrPath(const AttrPath & attrPath)
{
string s;
foreach (AttrPath::const_iterator, i, attrPath) {
if (!s.empty()) s += '.';
s += *i;
}
return s;
}
Pos noPos;
/* Computing levels/displacements for variables. */
void Expr::bindVars(const StaticEnv & env)
{
abort();
}
void ExprInt::bindVars(const StaticEnv & env)
{
}
void ExprString::bindVars(const StaticEnv & env)
{
}
void ExprPath::bindVars(const StaticEnv & env)
{
}
void ExprVar::bindVars(const StaticEnv & env)
{
/* Check whether the variable appears in the environment. If so,
set its level and displacement. */
const StaticEnv * curEnv;
unsigned int level;
int withLevel = -1;
for (curEnv = &env, level = 0; curEnv; curEnv = curEnv->up, level++) {
if (curEnv->isWith) {
if (withLevel == -1) withLevel = level;
} else {
StaticEnv::Vars::const_iterator i = curEnv->vars.find(name);
if (i != curEnv->vars.end()) {
fromWith = false;
this->level = level;
displ = i->second;
return;
}
}
}
/* Otherwise, the variable must be obtained from the nearest
enclosing `with'. If there is no `with', then we can issue an
"undefined variable" error now. */
if (withLevel == -1) throw UndefinedVarError(format("undefined variable `%1%' at %2%") % name % pos);
fromWith = true;
this->level = withLevel;
}
void ExprSelect::bindVars(const StaticEnv & env)
{
e->bindVars(env);
if (def) def->bindVars(env);
}
void ExprOpHasAttr::bindVars(const StaticEnv & env)
{
e->bindVars(env);
}
void ExprAttrs::bindVars(const StaticEnv & env)
{
if (recursive) {
StaticEnv newEnv(false, &env);
unsigned int displ = 0;
foreach (AttrDefs::iterator, i, attrs)
newEnv.vars[i->first] = i->second.displ = displ++;
foreach (AttrDefs::iterator, i, attrs)
i->second.e->bindVars(i->second.inherited ? env : newEnv);
}
else
foreach (AttrDefs::iterator, i, attrs)
i->second.e->bindVars(env);
}
void ExprList::bindVars(const StaticEnv & env)
{
foreach (vector<Expr *>::iterator, i, elems)
(*i)->bindVars(env);
}
void ExprLambda::bindVars(const StaticEnv & env)
{
StaticEnv newEnv(false, &env);
unsigned int displ = 0;
if (!arg.empty()) newEnv.vars[arg] = displ++;
if (matchAttrs) {
foreach (Formals::Formals_::iterator, i, formals->formals)
newEnv.vars[i->name] = displ++;
foreach (Formals::Formals_::iterator, i, formals->formals)
if (i->def) i->def->bindVars(newEnv);
}
body->bindVars(newEnv);
}
void ExprLet::bindVars(const StaticEnv & env)
{
StaticEnv newEnv(false, &env);
unsigned int displ = 0;
foreach (ExprAttrs::AttrDefs::iterator, i, attrs->attrs)
newEnv.vars[i->first] = i->second.displ = displ++;
foreach (ExprAttrs::AttrDefs::iterator, i, attrs->attrs)
i->second.e->bindVars(i->second.inherited ? env : newEnv);
body->bindVars(newEnv);
}
void ExprWith::bindVars(const StaticEnv & env)
{
/* Does this `with' have an enclosing `with'? If so, record its
level so that `lookupVar' can look up variables in the previous
`with' if this one doesn't contain the desired attribute. */
const StaticEnv * curEnv;
unsigned int level;
prevWith = 0;
for (curEnv = &env, level = 1; curEnv; curEnv = curEnv->up, level++)
if (curEnv->isWith) {
prevWith = level;
break;
}
attrs->bindVars(env);
StaticEnv newEnv(true, &env);
body->bindVars(newEnv);
}
void ExprIf::bindVars(const StaticEnv & env)
{
cond->bindVars(env);
then->bindVars(env);
else_->bindVars(env);
}
void ExprAssert::bindVars(const StaticEnv & env)
{
cond->bindVars(env);
body->bindVars(env);
}
void ExprOpNot::bindVars(const StaticEnv & env)
{
e->bindVars(env);
}
void ExprBuiltin::bindVars(const StaticEnv & env)
{
}
void ExprConcatStrings::bindVars(const StaticEnv & env)
{
foreach (vector<Expr *>::iterator, i, *es)
(*i)->bindVars(env);
}
void ExprPos::bindVars(const StaticEnv & env)
{
}
/* Storing function names. */
void Expr::setName(Symbol & name)
{
}
void ExprLambda::setName(Symbol & name)
{
this->name = name;
body->setName(name);
}
string ExprLambda::showNamePos() const
{
return (format("%1% at %2%") % (name.set() ? "`" + (string) name + "'" : "an anonymous function") % pos).str();
}
/* Symbol table. */
size_t SymbolTable::totalSize() const
{
size_t n = 0;
foreach (Symbols::const_iterator, i, symbols)
n += i->size();
return n;
}
}