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Simplify inherited attribute handling 

This reduces the difference between inherited and non-inherited
attribute handling to the choice of which env to use (in recs and lets)
by setting the AttrDef::e to a new ExprVar in the parser rather than
carrying a separate AttrDef::v VarRef member.

As an added bonus, this allows inherited attributes that inherit from a
with to delay forcing evaluation of the with's attributes.

Signed-off-by: Shea Levy <shea@shealevy.com>
This commit is contained in:
Shea Levy 2013-07-15 17:10:18 -04:00 committed by Eelco Dolstra
parent 6cd6ce5608
commit afc6c1bad6
7 changed files with 46 additions and 38 deletions
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40
src/libexpr/eval.cc
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@ -521,23 +521,17 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
environment, while the inherited attributes are evaluated
in the original environment. */
unsigned int displ = 0;
foreach (AttrDefs::iterator, i, attrs)
if (i->second.inherited) {
/* !!! handle overrides? */
Value * vAttr = state.lookupVar(&env, i->second.var);
env2.values[displ++] = vAttr;
v.attrs->push_back(Attr(i->first, vAttr, &i->second.pos));
} else {
Value * vAttr;
if (hasOverrides) {
vAttr = state.allocValue();
mkThunk(*vAttr, env2, i->second.e);
} else
vAttr = i->second.e->maybeThunk(state, env2);
env2.values[displ++] = vAttr;
v.attrs->push_back(Attr(i->first, vAttr, &i->second.pos));
}
foreach (AttrDefs::iterator, i, attrs) {
Value * vAttr;
if (hasOverrides && !i->second.inherited) {
vAttr = state.allocValue();
mkThunk(*vAttr, env2, i->second.e);
} else
vAttr = i->second.e->maybeThunk(state, i->second.inherited ? env : env2);
env2.values[displ++] = vAttr;
v.attrs->push_back(Attr(i->first, vAttr, &i->second.pos));
}
/* If the rec contains an attribute called `__overrides', then
evaluate it, and add the attributes in that set to the rec.
This allows overriding of recursive attributes, which is
@ -563,10 +557,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
else {
foreach (AttrDefs::iterator, i, attrs)
if (i->second.inherited)
v.attrs->push_back(Attr(i->first, state.lookupVar(&env, i->second.var), &i->second.pos));
else
v.attrs->push_back(Attr(i->first, i->second.e->maybeThunk(state, env), &i->second.pos));
v.attrs->push_back(Attr(i->first, i->second.e->maybeThunk(state, env), &i->second.pos));
}
}
@ -583,10 +574,7 @@ void ExprLet::eval(EvalState & state, Env & env, Value & v)
environment. */
unsigned int displ = 0;
foreach (ExprAttrs::AttrDefs::iterator, i, attrs->attrs)
if (i->second.inherited)
env2.values[displ++] = state.lookupVar(&env, i->second.var);
else
env2.values[displ++] = i->second.e->maybeThunk(state, env2);
env2.values[displ++] = i->second.e->maybeThunk(state, i->second.inherited ? env : env2);
body->eval(state, env2, v);
}
@ -602,7 +590,7 @@ void ExprList::eval(EvalState & state, Env & env, Value & v)
void ExprVar::eval(EvalState & state, Env & env, Value & v)
{
Value * v2 = state.lookupVar(&env, info);
Value * v2 = state.lookupVar(&env, info, false);
state.forceValue(*v2);
v = *v2;
}

2
src/libexpr/eval.hh
View File

@ -206,7 +206,7 @@ private:
void addPrimOp(const string & name,
unsigned int arity, PrimOpFun primOp);
inline Value * lookupVar(Env * env, const VarRef & var, bool noEval = false);
inline Value * lookupVar(Env * env, const VarRef & var, bool noEval);
friend class ExprVar;
friend class ExprAttrs;

9
src/libexpr/nixexpr.cc
View File

@ -230,14 +230,12 @@ void ExprAttrs::bindVars(const StaticEnv & env)
newEnv.vars[i->first] = i->second.displ = displ++;
foreach (AttrDefs::iterator, i, attrs)
if (i->second.inherited) i->second.var.bind(env);
else i->second.e->bindVars(newEnv);
i->second.e->bindVars(i->second.inherited ? env : newEnv);
}
else
foreach (AttrDefs::iterator, i, attrs)
if (i->second.inherited) i->second.var.bind(env);
else i->second.e->bindVars(env);
i->second.e->bindVars(env);
}
void ExprList::bindVars(const StaticEnv & env)
@ -274,8 +272,7 @@ void ExprLet::bindVars(const StaticEnv & env)
newEnv.vars[i->first] = i->second.displ = displ++;
foreach (ExprAttrs::AttrDefs::iterator, i, attrs->attrs)
if (i->second.inherited) i->second.var.bind(env);
else i->second.e->bindVars(newEnv);
i->second.e->bindVars(i->second.inherited ? env : newEnv);
body->bindVars(newEnv);
}

6
src/libexpr/nixexpr.hh
View File

@ -159,12 +159,10 @@ struct ExprAttrs : Expr
bool recursive;
struct AttrDef {
bool inherited;
Expr * e; // if not inherited
VarRef var; // if inherited
Expr * e;
Pos pos;
unsigned int displ; // displacement
AttrDef(Expr * e, const Pos & pos) : inherited(false), e(e), pos(pos) { };
AttrDef(const Symbol & name, const Pos & pos) : inherited(true), var(name), pos(pos) { };
AttrDef(Expr * e, const Pos & pos, bool inherited=false) : inherited(inherited), e(e), pos(pos) { };
AttrDef() { };
};
typedef std::map<Symbol, AttrDef> AttrDefs;

2
src/libexpr/parser.y
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@ -413,7 +413,7 @@ binds
if ($$->attrs.find(*i) != $$->attrs.end())
dupAttr(*i, makeCurPos(@3, data), $$->attrs[*i].pos);
Pos pos = makeCurPos(@3, data);
$$->attrs[*i] = ExprAttrs::AttrDef(*i, pos);
$$->attrs[*i] = ExprAttrs::AttrDef(new ExprVar(*i), pos, true);
}
}
| binds INHERIT '(' expr ')' attrs ';'

1
tests/lang/eval-okay-delayed-with-inherit.exp Normal file
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@ -0,0 +1 @@
"b-overridden"

24
tests/lang/eval-okay-delayed-with-inherit.nix Normal file
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@ -0,0 +1,24 @@
let
pkgs_ = with pkgs; {
a = derivation {
name = "a";
system = builtins.currentSystem;
builder = "/bin/sh";
args = [ "-c" "touch $out" ];
inherit b;
};
inherit b;
};
packageOverrides = p: {
b = derivation {
name = "b-overridden";
system = builtins.currentSystem;
builder = "/bin/sh";
args = [ "-c" "touch $out" ];
};
};
pkgs = pkgs_ // (packageOverrides pkgs_);
in pkgs.a.b.name