1 //! Trait solving using Chalk.
5 use chalk_ir::GoalData;
6 use chalk_recursive::Cache;
7 use chalk_solve::{logging_db::LoggingRustIrDatabase, Solver};
10 use hir_def::{lang_item::LangItemTarget, TraitId};
11 use stdx::panic_context;
15 db::HirDatabase, AliasEq, AliasTy, Canonical, DomainGoal, Goal, Guidance, InEnvironment,
16 Interner, Solution, TraitRefExt, Ty, TyKind, WhereClause,
19 /// This controls how much 'time' we give the Chalk solver before giving up.
20 const CHALK_SOLVER_FUEL: i32 = 100;
22 #[derive(Debug, Copy, Clone)]
23 pub(crate) struct ChalkContext<'a> {
24 pub(crate) db: &'a dyn HirDatabase,
25 pub(crate) krate: CrateId,
28 fn create_chalk_solver() -> chalk_recursive::RecursiveSolver<Interner> {
30 var("CHALK_OVERFLOW_DEPTH").ok().and_then(|s| s.parse().ok()).unwrap_or(300);
31 let max_size = var("CHALK_SOLVER_MAX_SIZE").ok().and_then(|s| s.parse().ok()).unwrap_or(150);
32 chalk_recursive::RecursiveSolver::new(overflow_depth, max_size, Some(Cache::new()))
35 /// A set of clauses that we assume to be true. E.g. if we are inside this function:
37 /// fn foo<T: Default>(t: T) {}
39 /// we assume that `T: Default`.
40 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
41 pub struct TraitEnvironment {
43 // When we're using Chalk's Ty we can make this a BTreeMap since it's Ord,
44 // but for now it's too annoying...
45 pub(crate) traits_from_clauses: Vec<(Ty, TraitId)>,
46 pub env: chalk_ir::Environment<Interner>,
49 impl TraitEnvironment {
50 pub fn empty(krate: CrateId) -> Self {
53 traits_from_clauses: Vec::new(),
54 env: chalk_ir::Environment::new(Interner),
58 pub fn traits_in_scope_from_clauses<'a>(
61 ) -> impl Iterator<Item = TraitId> + 'a {
62 self.traits_from_clauses
64 .filter_map(move |(self_ty, trait_id)| (*self_ty == ty).then(|| *trait_id))
68 /// Solve a trait goal using Chalk.
69 pub(crate) fn trait_solve_query(
72 goal: Canonical<InEnvironment<Goal>>,
73 ) -> Option<Solution> {
74 let _p = profile::span("trait_solve_query").detail(|| match &goal.value.goal.data(Interner) {
75 GoalData::DomainGoal(DomainGoal::Holds(WhereClause::Implemented(it))) => {
76 db.trait_data(it.hir_trait_id()).name.to_string()
78 GoalData::DomainGoal(DomainGoal::Holds(WhereClause::AliasEq(_))) => "alias_eq".to_string(),
79 _ => "??".to_string(),
81 tracing::info!("trait_solve_query({:?})", goal.value.goal);
83 if let GoalData::DomainGoal(DomainGoal::Holds(WhereClause::AliasEq(AliasEq {
84 alias: AliasTy::Projection(projection_ty),
86 }))) = &goal.value.goal.data(Interner)
88 if let TyKind::BoundVar(_) = projection_ty.self_type_parameter(Interner).kind(Interner) {
89 // Hack: don't ask Chalk to normalize with an unknown self type, it'll say that's impossible
90 return Some(Solution::Ambig(Guidance::Unknown));
94 // We currently don't deal with universes (I think / hope they're not yet
95 // relevant for our use cases?)
96 let u_canonical = chalk_ir::UCanonical { canonical: goal, universes: 1 };
97 solve(db, krate, &u_canonical)
101 db: &dyn HirDatabase,
103 goal: &chalk_ir::UCanonical<chalk_ir::InEnvironment<chalk_ir::Goal<Interner>>>,
104 ) -> Option<chalk_solve::Solution<Interner>> {
105 let context = ChalkContext { db, krate };
106 tracing::debug!("solve goal: {:?}", goal);
107 let mut solver = create_chalk_solver();
109 let fuel = std::cell::Cell::new(CHALK_SOLVER_FUEL);
111 let should_continue = || {
112 db.unwind_if_cancelled();
113 let remaining = fuel.get();
114 fuel.set(remaining - 1);
116 tracing::debug!("fuel exhausted");
122 let _ctx = if is_chalk_debug() || is_chalk_print() {
123 Some(panic_context::enter(format!("solving {:?}", goal)))
127 let solution = if is_chalk_print() {
129 LoggingRustIrDatabaseLoggingOnDrop(LoggingRustIrDatabase::new(context));
130 solver.solve_limited(&logging_db.0, goal, &should_continue)
132 solver.solve_limited(&context, goal, &should_continue)
135 tracing::debug!("solve({:?}) => {:?}", goal, solution);
140 // don't set the TLS for Chalk unless Chalk debugging is active, to make
141 // extra sure we only use it for debugging
142 if is_chalk_debug() {
143 crate::tls::set_current_program(db, solve)
149 struct LoggingRustIrDatabaseLoggingOnDrop<'a>(LoggingRustIrDatabase<Interner, ChalkContext<'a>>);
151 impl<'a> Drop for LoggingRustIrDatabaseLoggingOnDrop<'a> {
153 eprintln!("chalk program:\n{}", self.0);
157 fn is_chalk_debug() -> bool {
158 std::env::var("CHALK_DEBUG").is_ok()
161 fn is_chalk_print() -> bool {
162 std::env::var("CHALK_PRINT").is_ok()
165 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
173 const fn lang_item_name(self) -> &'static str {
175 FnTrait::FnOnce => "fn_once",
176 FnTrait::FnMut => "fn_mut",
181 pub fn get_id(&self, db: &dyn HirDatabase, krate: CrateId) -> Option<TraitId> {
182 let target = db.lang_item(krate, SmolStr::new_inline(self.lang_item_name()))?;
184 LangItemTarget::TraitId(t) => Some(t),