style: rename crates to kebab case

crates/hir-ty/src/traits.rs

@@ -0,0 +1,187 @@
+//! Trait solving using Chalk.
+
+use std::env::var;
+
+use chalk_ir::GoalData;
+use chalk_recursive::Cache;
+use chalk_solve::{logging_db::LoggingRustIrDatabase, Solver};
+
+use base_db::CrateId;
+use hir_def::{lang_item::LangItemTarget, TraitId};
+use stdx::panic_context;
+use syntax::SmolStr;
+
+use crate::{
+    db::HirDatabase, AliasEq, AliasTy, Canonical, DomainGoal, Goal, Guidance, InEnvironment,
+    Interner, Solution, TraitRefExt, Ty, TyKind, WhereClause,
+};
+
+/// This controls how much 'time' we give the Chalk solver before giving up.
+const CHALK_SOLVER_FUEL: i32 = 100;
+
+#[derive(Debug, Copy, Clone)]
+pub(crate) struct ChalkContext<'a> {
+    pub(crate) db: &'a dyn HirDatabase,
+    pub(crate) krate: CrateId,
+}
+
+fn create_chalk_solver() -> chalk_recursive::RecursiveSolver<Interner> {
+    let overflow_depth =
+        var("CHALK_OVERFLOW_DEPTH").ok().and_then(|s| s.parse().ok()).unwrap_or(300);
+    let max_size = var("CHALK_SOLVER_MAX_SIZE").ok().and_then(|s| s.parse().ok()).unwrap_or(150);
+    chalk_recursive::RecursiveSolver::new(overflow_depth, max_size, Some(Cache::new()))
+}
+
+/// A set of clauses that we assume to be true. E.g. if we are inside this function:
+/// ```rust
+/// fn foo<T: Default>(t: T) {}
+/// ```
+/// we assume that `T: Default`.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct TraitEnvironment {
+    pub krate: CrateId,
+    // FIXME make this a BTreeMap
+    pub(crate) traits_from_clauses: Vec<(Ty, TraitId)>,
+    pub env: chalk_ir::Environment<Interner>,
+}
+
+impl TraitEnvironment {
+    pub fn empty(krate: CrateId) -> Self {
+        TraitEnvironment {
+            krate,
+            traits_from_clauses: Vec::new(),
+            env: chalk_ir::Environment::new(Interner),
+        }
+    }
+
+    pub fn traits_in_scope_from_clauses<'a>(
+        &'a self,
+        ty: Ty,
+    ) -> impl Iterator<Item = TraitId> + 'a {
+        self.traits_from_clauses
+            .iter()
+            .filter_map(move |(self_ty, trait_id)| (*self_ty == ty).then(|| *trait_id))
+    }
+}
+
+/// Solve a trait goal using Chalk.
+pub(crate) fn trait_solve_query(
+    db: &dyn HirDatabase,
+    krate: CrateId,
+    goal: Canonical<InEnvironment<Goal>>,
+) -> Option<Solution> {
+    let _p = profile::span("trait_solve_query").detail(|| match &goal.value.goal.data(Interner) {
+        GoalData::DomainGoal(DomainGoal::Holds(WhereClause::Implemented(it))) => {
+            db.trait_data(it.hir_trait_id()).name.to_string()
+        }
+        GoalData::DomainGoal(DomainGoal::Holds(WhereClause::AliasEq(_))) => "alias_eq".to_string(),
+        _ => "??".to_string(),
+    });
+    tracing::info!("trait_solve_query({:?})", goal.value.goal);
+
+    if let GoalData::DomainGoal(DomainGoal::Holds(WhereClause::AliasEq(AliasEq {
+        alias: AliasTy::Projection(projection_ty),
+        ..
+    }))) = &goal.value.goal.data(Interner)
+    {
+        if let TyKind::BoundVar(_) = projection_ty.self_type_parameter(Interner).kind(Interner) {
+            // Hack: don't ask Chalk to normalize with an unknown self type, it'll say that's impossible
+            return Some(Solution::Ambig(Guidance::Unknown));
+        }
+    }
+
+    // We currently don't deal with universes (I think / hope they're not yet
+    // relevant for our use cases?)
+    let u_canonical = chalk_ir::UCanonical { canonical: goal, universes: 1 };
+    solve(db, krate, &u_canonical)
+}
+
+fn solve(
+    db: &dyn HirDatabase,
+    krate: CrateId,
+    goal: &chalk_ir::UCanonical<chalk_ir::InEnvironment<chalk_ir::Goal<Interner>>>,
+) -> Option<chalk_solve::Solution<Interner>> {
+    let context = ChalkContext { db, krate };
+    tracing::debug!("solve goal: {:?}", goal);
+    let mut solver = create_chalk_solver();
+
+    let fuel = std::cell::Cell::new(CHALK_SOLVER_FUEL);
+
+    let should_continue = || {
+        db.unwind_if_cancelled();
+        let remaining = fuel.get();
+        fuel.set(remaining - 1);
+        if remaining == 0 {
+            tracing::debug!("fuel exhausted");
+        }
+        remaining > 0
+    };
+
+    let mut solve = || {
+        let _ctx = if is_chalk_debug() || is_chalk_print() {
+            Some(panic_context::enter(format!("solving {:?}", goal)))
+        } else {
+            None
+        };
+        let solution = if is_chalk_print() {
+            let logging_db =
+                LoggingRustIrDatabaseLoggingOnDrop(LoggingRustIrDatabase::new(context));
+            solver.solve_limited(&logging_db.0, goal, &should_continue)
+        } else {
+            solver.solve_limited(&context, goal, &should_continue)
+        };
+
+        tracing::debug!("solve({:?}) => {:?}", goal, solution);
+
+        solution
+    };
+
+    // don't set the TLS for Chalk unless Chalk debugging is active, to make
+    // extra sure we only use it for debugging
+    if is_chalk_debug() {
+        crate::tls::set_current_program(db, solve)
+    } else {
+        solve()
+    }
+}
+
+struct LoggingRustIrDatabaseLoggingOnDrop<'a>(LoggingRustIrDatabase<Interner, ChalkContext<'a>>);
+
+impl<'a> Drop for LoggingRustIrDatabaseLoggingOnDrop<'a> {
+    fn drop(&mut self) {
+        eprintln!("chalk program:\n{}", self.0);
+    }
+}
+
+fn is_chalk_debug() -> bool {
+    std::env::var("CHALK_DEBUG").is_ok()
+}
+
+fn is_chalk_print() -> bool {
+    std::env::var("CHALK_PRINT").is_ok()
+}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub enum FnTrait {
+    FnOnce,
+    FnMut,
+    Fn,
+}
+
+impl FnTrait {
+    const fn lang_item_name(self) -> &'static str {
+        match self {
+            FnTrait::FnOnce => "fn_once",
+            FnTrait::FnMut => "fn_mut",
+            FnTrait::Fn => "fn",
+        }
+    }
+
+    pub fn get_id(&self, db: &dyn HirDatabase, krate: CrateId) -> Option<TraitId> {
+        let target = db.lang_item(krate, SmolStr::new_inline(self.lang_item_name()))?;
+        match target {
+            LangItemTarget::TraitId(t) => Some(t),
+            _ => None,
+        }
+    }
+}