lix/src/libexpr/nixexpr.cc

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#include "nixexpr.hh"
#include "derivations.hh"
#include "util.hh"
#include <cstdlib>
namespace nix {
/* Displaying abstract syntax trees. */
std::ostream & operator << (std::ostream & str, const Expr & e)
{
e.show(str);
return str;
}
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static void showString(std::ostream & str, const string & s)
{
str << '"';
for (auto c : (string) s)
if (c == '"' || c == '\\' || c == '$') str << "\\" << c;
else if (c == '\n') str << "\\n";
else if (c == '\r') str << "\\r";
else if (c == '\t') str << "\\t";
else str << c;
str << '"';
}
static void showId(std::ostream & str, const string & s)
{
if (s.empty())
str << "\"\"";
else if (s == "if") // FIXME: handle other keywords
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str << '"' << s << '"';
else {
char c = s[0];
if (!((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_')) {
showString(str, s);
return;
}
for (auto c : s)
if (!((c >= 'a' && c <= 'z') ||
(c >= 'A' && c <= 'Z') ||
(c >= '0' && c <= '9') ||
c == '_' || c == '\'' || c == '-')) {
showString(str, s);
return;
}
str << s;
}
}
std::ostream & operator << (std::ostream & str, const Symbol & sym)
{
showId(str, *sym.s);
return str;
}
void Expr::show(std::ostream & str) const
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{
abort();
}
void ExprInt::show(std::ostream & str) const
{
str << n;
}
void ExprFloat::show(std::ostream & str) const
{
str << nf;
}
void ExprString::show(std::ostream & str) const
{
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showString(str, s);
}
void ExprPath::show(std::ostream & str) const
{
str << s;
}
void ExprVar::show(std::ostream & str) const
{
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str << name;
}
void ExprSelect::show(std::ostream & str) const
{
str << "(" << *e << ")." << showAttrPath(attrPath);
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if (def) str << " or (" << *def << ")";
}
void ExprOpHasAttr::show(std::ostream & str) const
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{
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str << "((" << *e << ") ? " << showAttrPath(attrPath) << ")";
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}
void ExprAttrs::show(std::ostream & str) const
{
if (recursive) str << "rec ";
str << "{ ";
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for (auto & i : attrs)
if (i.second.inherited)
str << "inherit " << i.first << " " << "; ";
else
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str << i.first << " = " << *i.second.e << "; ";
for (auto & i : dynamicAttrs)
str << "\"${" << *i.nameExpr << "}\" = " << *i.valueExpr << "; ";
str << "}";
}
void ExprList::show(std::ostream & str) const
{
str << "[ ";
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for (auto & i : elems)
str << "(" << *i << ") ";
str << "]";
}
void ExprLambda::show(std::ostream & str) const
{
str << "(";
if (hasFormals()) {
str << "{ ";
bool first = true;
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for (auto & i : formals->formals) {
if (first) first = false; else str << ", ";
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str << i.name;
if (i.def) str << " ? " << *i.def;
}
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if (formals->ellipsis) {
if (!first) str << ", ";
str << "...";
}
str << " }";
if (!arg.empty()) str << " @ ";
}
if (!arg.empty()) str << arg;
str << ": " << *body << ")";
}
void ExprCall::show(std::ostream & str) const
{
str << '(' << *fun;
for (auto e : args) {
str << ' ';
str << *e;
}
str << ')';
}
void ExprLet::show(std::ostream & str) const
{
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str << "(let ";
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for (auto & i : attrs->attrs)
if (i.second.inherited) {
str << "inherit " << i.first << "; ";
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}
else
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str << i.first << " = " << *i.second.e << "; ";
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str << "in " << *body << ")";
}
void ExprWith::show(std::ostream & str) const
{
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str << "(with " << *attrs << "; " << *body << ")";
}
void ExprIf::show(std::ostream & str) const
{
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str << "(if " << *cond << " then " << *then << " else " << *else_ << ")";
}
void ExprAssert::show(std::ostream & str) const
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{
str << "assert " << *cond << "; " << *body;
}
void ExprOpNot::show(std::ostream & str) const
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{
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str << "(! " << *e << ")";
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}
void ExprConcatStrings::show(std::ostream & str) const
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{
bool first = true;
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str << "(";
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for (auto & i : *es) {
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if (first) first = false; else str << " + ";
str << i.second;
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}
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str << ")";
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}
void ExprPos::show(std::ostream & str) const
{
str << "__curPos";
}
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std::ostream & operator << (std::ostream & str, const Pos & pos)
{
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if (!pos)
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str << "undefined position";
else
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{
auto f = format(ANSI_BOLD "%1%" ANSI_NORMAL ":%2%:%3%");
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switch (pos.origin) {
case foFile:
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f % (string) pos.file;
break;
case foStdin:
case foString:
f % "(string)";
break;
default:
throw Error("unhandled Pos origin!");
}
str << (f % pos.line % pos.column).str();
}
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return str;
}
string showAttrPath(const AttrPath & attrPath)
{
std::ostringstream out;
bool first = true;
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for (auto & i : attrPath) {
if (!first) out << '.'; else first = false;
if (i.symbol.set())
out << i.symbol;
else
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out << "\"${" << *i.expr << "}\"";
}
return out.str();
}
Pos noPos;
/* Computing levels/displacements for variables. */
void Expr::bindVars(const StaticEnv & env)
{
abort();
}
void ExprInt::bindVars(const StaticEnv & env)
{
}
void ExprFloat::bindVars(const StaticEnv & env)
{
}
void ExprString::bindVars(const StaticEnv & env)
{
}
void ExprPath::bindVars(const StaticEnv & env)
{
}
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void ExprVar::bindVars(const StaticEnv & env)
{
/* Check whether the variable appears in the environment. If so,
set its level and displacement. */
const StaticEnv * curEnv;
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Level level;
int withLevel = -1;
for (curEnv = &env, level = 0; curEnv; curEnv = curEnv->up, level++) {
if (curEnv->isWith) {
if (withLevel == -1) withLevel = level;
} else {
auto i = curEnv->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. */
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if (withLevel == -1)
throw UndefinedVarError({
Improve error formatting Changes: * The divider lines are gone. These were in practice a bit confusing, in particular with --show-trace or --keep-going, since then there were multiple lines, suggesting a start/end which wasn't the case. * Instead, multi-line error messages are now indented to align with the prefix (e.g. "error: "). * The 'description' field is gone since we weren't really using it. * 'hint' is renamed to 'msg' since it really wasn't a hint. * The error is now printed *before* the location info. * The 'name' field is no longer printed since most of the time it wasn't very useful since it was just the name of the exception (like EvalError). Ideally in the future this would be a unique, easily googleable error ID (like rustc). * "trace:" is now just "…". This assumes error contexts start with something like "while doing X". Example before: error: --- AssertionError ---------------------------------------------------------------------------------------- nix at: (7:7) in file: /home/eelco/Dev/nixpkgs/pkgs/applications/misc/hello/default.nix 6| 7| x = assert false; 1; | ^ 8| assertion 'false' failed ----------------------------------------------------- show-trace ----------------------------------------------------- trace: while evaluating the attribute 'x' of the derivation 'hello-2.10' at: (192:11) in file: /home/eelco/Dev/nixpkgs/pkgs/stdenv/generic/make-derivation.nix 191| // (lib.optionalAttrs (!(attrs ? name) && attrs ? pname && attrs ? version)) { 192| name = "${attrs.pname}-${attrs.version}"; | ^ 193| } // (lib.optionalAttrs (stdenv.hostPlatform != stdenv.buildPlatform && !dontAddHostSuffix && (attrs ? name || (attrs ? pname && attrs ? version)))) { Example after: error: assertion 'false' failed at: (7:7) in file: /home/eelco/Dev/nixpkgs/pkgs/applications/misc/hello/default.nix 6| 7| x = assert false; 1; | ^ 8| … while evaluating the attribute 'x' of the derivation 'hello-2.10' at: (192:11) in file: /home/eelco/Dev/nixpkgs/pkgs/stdenv/generic/make-derivation.nix 191| // (lib.optionalAttrs (!(attrs ? name) && attrs ? pname && attrs ? version)) { 192| name = "${attrs.pname}-${attrs.version}"; | ^ 193| } // (lib.optionalAttrs (stdenv.hostPlatform != stdenv.buildPlatform && !dontAddHostSuffix && (attrs ? name || (attrs ? pname && attrs ? version)))) {
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.msg = hintfmt("undefined variable '%1%'", name),
.errPos = pos
});
fromWith = true;
this->level = withLevel;
}
void ExprSelect::bindVars(const StaticEnv & env)
{
e->bindVars(env);
if (def) def->bindVars(env);
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for (auto & i : attrPath)
if (!i.symbol.set())
i.expr->bindVars(env);
}
void ExprOpHasAttr::bindVars(const StaticEnv & env)
{
e->bindVars(env);
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for (auto & i : attrPath)
if (!i.symbol.set())
i.expr->bindVars(env);
}
void ExprAttrs::bindVars(const StaticEnv & env)
{
const StaticEnv * dynamicEnv = &env;
StaticEnv newEnv(false, &env, recursive ? attrs.size() : 0);
if (recursive) {
Dynamic attrs This adds new syntax for attribute names: * attrs."${name}" => getAttr name attrs * attrs ? "${name}" => isAttrs attrs && hasAttr attrs name * attrs."${name}" or def => if attrs ? "${name}" then attrs."${name}" else def * { "${name}" = value; } => listToAttrs [{ inherit name value; }] Of course, it's a bit more complicated than that. The attribute chains can be arbitrarily long and contain combinations of static and dynamic parts (e.g. attrs."${foo}".bar."${baz}" or qux), which is relatively straightforward for the getAttrs/hasAttrs cases but is more complex for the listToAttrs case due to rules about duplicate attribute definitions. For attribute sets with dynamic attribute names, duplicate static attributes are detected at parse time while duplicate dynamic attributes are detected when the attribute set is forced. So, for example, { a = null; a.b = null; "${"c"}" = true; } will be a parse-time error, while { a = {}; "${"a"}".b = null; c = true; } will be an eval-time error (technically that case could theoretically be detected at parse time, but the general case would require full evaluation). Moreover, duplicate dynamic attributes are not allowed even in cases where they would be with static attributes ({ a.b.d = true; a.b.c = false; } is legal, but { a."${"b"}".d = true; a."${"b"}".c = false; } is not). This restriction might be relaxed in the future in cases where the static variant would not be an error, but it is not obvious that that is desirable. Finally, recursive attribute sets with dynamic attributes have the static attributes in scope but not the dynamic ones. So rec { a = true; "${"b"}" = a; } is equivalent to { a = true; b = true; } but rec { "${"a"}" = true; b = a; } would be an error or use a from the surrounding scope if it exists. Note that the getAttr, getAttr or default, and hasAttr are all implemented purely in the parser as syntactic sugar, while attribute sets with dynamic attribute names required changes to the AST to be implemented cleanly. This is an alternative solution to and closes #167 Signed-off-by: Shea Levy <shea@shealevy.com>
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dynamicEnv = &newEnv;
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Displacement displ = 0;
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for (auto & i : attrs)
newEnv.vars.emplace_back(i.first, i.second.displ = displ++);
// No need to sort newEnv since attrs is in sorted order.
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for (auto & i : attrs)
i.second.e->bindVars(i.second.inherited ? env : newEnv);
}
else
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for (auto & i : attrs)
i.second.e->bindVars(env);
Dynamic attrs This adds new syntax for attribute names: * attrs."${name}" => getAttr name attrs * attrs ? "${name}" => isAttrs attrs && hasAttr attrs name * attrs."${name}" or def => if attrs ? "${name}" then attrs."${name}" else def * { "${name}" = value; } => listToAttrs [{ inherit name value; }] Of course, it's a bit more complicated than that. The attribute chains can be arbitrarily long and contain combinations of static and dynamic parts (e.g. attrs."${foo}".bar."${baz}" or qux), which is relatively straightforward for the getAttrs/hasAttrs cases but is more complex for the listToAttrs case due to rules about duplicate attribute definitions. For attribute sets with dynamic attribute names, duplicate static attributes are detected at parse time while duplicate dynamic attributes are detected when the attribute set is forced. So, for example, { a = null; a.b = null; "${"c"}" = true; } will be a parse-time error, while { a = {}; "${"a"}".b = null; c = true; } will be an eval-time error (technically that case could theoretically be detected at parse time, but the general case would require full evaluation). Moreover, duplicate dynamic attributes are not allowed even in cases where they would be with static attributes ({ a.b.d = true; a.b.c = false; } is legal, but { a."${"b"}".d = true; a."${"b"}".c = false; } is not). This restriction might be relaxed in the future in cases where the static variant would not be an error, but it is not obvious that that is desirable. Finally, recursive attribute sets with dynamic attributes have the static attributes in scope but not the dynamic ones. So rec { a = true; "${"b"}" = a; } is equivalent to { a = true; b = true; } but rec { "${"a"}" = true; b = a; } would be an error or use a from the surrounding scope if it exists. Note that the getAttr, getAttr or default, and hasAttr are all implemented purely in the parser as syntactic sugar, while attribute sets with dynamic attribute names required changes to the AST to be implemented cleanly. This is an alternative solution to and closes #167 Signed-off-by: Shea Levy <shea@shealevy.com>
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for (auto & i : dynamicAttrs) {
i.nameExpr->bindVars(*dynamicEnv);
i.valueExpr->bindVars(*dynamicEnv);
Dynamic attrs This adds new syntax for attribute names: * attrs."${name}" => getAttr name attrs * attrs ? "${name}" => isAttrs attrs && hasAttr attrs name * attrs."${name}" or def => if attrs ? "${name}" then attrs."${name}" else def * { "${name}" = value; } => listToAttrs [{ inherit name value; }] Of course, it's a bit more complicated than that. The attribute chains can be arbitrarily long and contain combinations of static and dynamic parts (e.g. attrs."${foo}".bar."${baz}" or qux), which is relatively straightforward for the getAttrs/hasAttrs cases but is more complex for the listToAttrs case due to rules about duplicate attribute definitions. For attribute sets with dynamic attribute names, duplicate static attributes are detected at parse time while duplicate dynamic attributes are detected when the attribute set is forced. So, for example, { a = null; a.b = null; "${"c"}" = true; } will be a parse-time error, while { a = {}; "${"a"}".b = null; c = true; } will be an eval-time error (technically that case could theoretically be detected at parse time, but the general case would require full evaluation). Moreover, duplicate dynamic attributes are not allowed even in cases where they would be with static attributes ({ a.b.d = true; a.b.c = false; } is legal, but { a."${"b"}".d = true; a."${"b"}".c = false; } is not). This restriction might be relaxed in the future in cases where the static variant would not be an error, but it is not obvious that that is desirable. Finally, recursive attribute sets with dynamic attributes have the static attributes in scope but not the dynamic ones. So rec { a = true; "${"b"}" = a; } is equivalent to { a = true; b = true; } but rec { "${"a"}" = true; b = a; } would be an error or use a from the surrounding scope if it exists. Note that the getAttr, getAttr or default, and hasAttr are all implemented purely in the parser as syntactic sugar, while attribute sets with dynamic attribute names required changes to the AST to be implemented cleanly. This is an alternative solution to and closes #167 Signed-off-by: Shea Levy <shea@shealevy.com>
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}
}
void ExprList::bindVars(const StaticEnv & env)
{
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for (auto & i : elems)
i->bindVars(env);
}
void ExprLambda::bindVars(const StaticEnv & env)
{
StaticEnv newEnv(
false, &env,
(hasFormals() ? formals->formals.size() : 0) +
(arg.empty() ? 0 : 1));
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Displacement displ = 0;
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if (!arg.empty()) newEnv.vars.emplace_back(arg, displ++);
if (hasFormals()) {
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for (auto & i : formals->formals)
newEnv.vars.emplace_back(i.name, displ++);
newEnv.sort();
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for (auto & i : formals->formals)
if (i.def) i.def->bindVars(newEnv);
}
body->bindVars(newEnv);
}
void ExprCall::bindVars(const StaticEnv & env)
{
fun->bindVars(env);
for (auto e : args)
e->bindVars(env);
}
void ExprLet::bindVars(const StaticEnv & env)
{
StaticEnv newEnv(false, &env, attrs->attrs.size());
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Displacement displ = 0;
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for (auto & i : attrs->attrs)
newEnv.vars.emplace_back(i.first, i.second.displ = displ++);
// No need to sort newEnv since attrs->attrs is in sorted order.
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for (auto & i : attrs->attrs)
i.second.e->bindVars(i.second.inherited ? env : newEnv);
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body->bindVars(newEnv);
}
void ExprWith::bindVars(const StaticEnv & env)
{
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/* 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. */
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const StaticEnv * curEnv;
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Level level;
prevWith = 0;
for (curEnv = &env, level = 1; curEnv; curEnv = curEnv->up, level++)
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if (curEnv->isWith) {
prevWith = level;
break;
}
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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 ExprConcatStrings::bindVars(const StaticEnv & env)
{
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for (auto & i : *es)
i.second->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);
}
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string ExprLambda::showNamePos() const
{
return (format("%1% at %2%") % (name.set() ? "'" + (string) name + "'" : "anonymous function") % pos).str();
}
/* Symbol table. */
size_t SymbolTable::totalSize() const
{
size_t n = 0;
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for (auto & i : symbols)
n += i.size();
return n;
}
}