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evaluate inherit (from) exprs only once per directive

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desugaring inherit-from to syntactic duplication of the source expr also
duplicates side effects of the source expr (such as trace calls) and
expensive computations (such as derivationStrict).

(cherry picked from commit cefd0302b55b3360dbca59cfcb4bf6a750d6cdcf)
Change-Id: Iff519f991adef2e51683ba2c552d37a3df7a179e
This commit is contained in:
eldritch horrors
2024-03-10 03:18:32 -06:00
parent 71e0114708
commit b667b4cded
9 changed files with 109 additions and 15 deletions
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src/libexpr/eval.cc
+20 -4
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@@ -1217,6 +1217,18 @@ void ExprPath::eval(EvalState & state, Env & env, Value & v)
}
Env * ExprAttrs::buildInheritFromEnv(EvalState & state, Env & up)
{
Env & inheritEnv = state.allocEnv(inheritFromExprs->size());
inheritEnv.up = &up;
Displacement displ = 0;
for (auto from : *inheritFromExprs)
inheritEnv.values[displ++] = from->maybeThunk(state, up);
return &inheritEnv;
}
void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
{
v.mkAttrs(state.buildBindings(attrs.size() + dynamicAttrs.size()).finish());
@@ -1228,6 +1240,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
Env & env2(state.allocEnv(attrs.size()));
env2.up = &env;
dynamicEnv = &env2;
Env * inheritEnv = inheritFromExprs ? buildInheritFromEnv(state, env2) : nullptr;
AttrDefs::iterator overrides = attrs.find(state.sOverrides);
bool hasOverrides = overrides != attrs.end();
@@ -1240,9 +1253,9 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
Value * vAttr;
if (hasOverrides && !i.second.inherited()) {
vAttr = state.allocValue();
mkThunk(*vAttr, *i.second.chooseByKind(&env2, &env, &env2), i.second.e);
mkThunk(*vAttr, *i.second.chooseByKind(&env2, &env, inheritEnv), i.second.e);
} else
vAttr = i.second.e->maybeThunk(state, *i.second.chooseByKind(&env2, &env, &env2));
vAttr = i.second.e->maybeThunk(state, *i.second.chooseByKind(&env2, &env, inheritEnv));
env2.values[displ++] = vAttr;
v.attrs->push_back(Attr(i.first, vAttr, i.second.pos));
}
@@ -1275,10 +1288,11 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
}
else {
Env * inheritEnv = inheritFromExprs ? buildInheritFromEnv(state, env) : nullptr;
for (auto & i : attrs) {
v.attrs->push_back(Attr(
i.first,
i.second.e->maybeThunk(state, *i.second.chooseByKind(&env, &env, &env)),
i.second.e->maybeThunk(state, *i.second.chooseByKind(&env, &env, inheritEnv)),
i.second.pos));
}
}
@@ -1313,6 +1327,8 @@ void ExprLet::eval(EvalState & state, Env & env, Value & v)
Env & env2(state.allocEnv(attrs->attrs.size()));
env2.up = &env;
Env * inheritEnv = attrs->inheritFromExprs ? attrs->buildInheritFromEnv(state, env2) : nullptr;
/* The recursive attributes are evaluated in the new environment,
while the inherited attributes are evaluated in the original
environment. */
@@ -1320,7 +1336,7 @@ void ExprLet::eval(EvalState & state, Env & env, Value & v)
for (auto & i : attrs->attrs) {
env2.values[displ++] = i.second.e->maybeThunk(
state,
*i.second.chooseByKind(&env2, &env, &env2));
*i.second.chooseByKind(&env2, &env, inheritEnv));
}
auto dts = state.debugRepl