Extract coercion logic to InferenceTable

To make it accessible without an InferenceContext.

crates/hir_ty/src/infer/coerce.rs

@@ -22,6 +22,8 @@ use crate::{
     Solution, Substitution, Ty, TyBuilder, TyExt, TyKind,
 };
 
+use super::unify::InferenceTable;
+
 pub(crate) type CoerceResult = Result<InferOk<(Vec<Adjustment>, Ty)>, TypeError>;
 
 /// Do not require any adjustments, i.e. coerce `x -> x`.
@@ -84,8 +86,8 @@ impl CoerceMany {
         };
         if let Some(sig) = sig {
             let target_ty = TyKind::Function(sig.to_fn_ptr()).intern(Interner);
-            let result1 = ctx.coerce_inner(self.expected_ty.clone(), &target_ty);
-            let result2 = ctx.coerce_inner(expr_ty.clone(), &target_ty);
+            let result1 = ctx.table.coerce_inner(self.expected_ty.clone(), &target_ty);
+            let result2 = ctx.table.coerce_inner(expr_ty.clone(), &target_ty);
             if let (Ok(result1), Ok(result2)) = (result1, result2) {
                 ctx.table.register_infer_ok(result1);
                 ctx.table.register_infer_ok(result2);
@@ -126,16 +128,31 @@ impl<'a> InferenceContext<'a> {
         expr: Option<ExprId>,
         from_ty: &Ty,
         to_ty: &Ty,
-    ) -> InferResult<Ty> {
+    ) -> Result<Ty, TypeError> {
+        let from_ty = self.resolve_ty_shallow(from_ty);
+        let to_ty = self.resolve_ty_shallow(to_ty);
+        let (adjustments, ty) = self.table.coerce(&from_ty, &to_ty)?;
+        if let Some(expr) = expr {
+            self.write_expr_adj(expr, adjustments);
+        }
+        Ok(ty)
+    }
+}
+
+impl<'a> InferenceTable<'a> {
+    /// Unify two types, but may coerce the first one to the second one
+    /// using "implicit coercion rules" if needed.
+    pub(crate) fn coerce(
+        &mut self,
+        from_ty: &Ty,
+        to_ty: &Ty,
+    ) -> Result<(Vec<Adjustment>, Ty), TypeError> {
         let from_ty = self.resolve_ty_shallow(from_ty);
         let to_ty = self.resolve_ty_shallow(to_ty);
         match self.coerce_inner(from_ty, &to_ty) {
             Ok(InferOk { value: (adjustments, ty), goals }) => {
-                if let Some(expr) = expr {
-                    self.write_expr_adj(expr, adjustments);
-                }
-                self.table.register_infer_ok(InferOk { value: (), goals });
-                Ok(InferOk { value: ty, goals: Vec::new() })
+                self.register_infer_ok(InferOk { value: (), goals });
+                Ok((adjustments, ty))
             }
             Err(e) => {
                 // FIXME deal with error
@@ -154,7 +171,7 @@ impl<'a> InferenceContext<'a> {
             //
             // here, we would coerce from `!` to `?T`.
             if let TyKind::InferenceVar(tv, TyVariableKind::General) = to_ty.kind(Interner) {
-                self.table.set_diverging(*tv, true);
+                self.set_diverging(*tv, true);
             }
             return success(simple(Adjust::NeverToAny)(to_ty.clone()), to_ty.clone(), vec![]);
         }
@@ -203,8 +220,7 @@ impl<'a> InferenceContext<'a> {
     where
         F: FnOnce(Ty) -> Vec<Adjustment>,
     {
-        self.table
-            .try_unify(t1, t2)
+        self.try_unify(t1, t2)
             .and_then(|InferOk { goals, .. }| success(f(t1.clone()), t1.clone(), goals))
     }
 
@@ -259,9 +275,9 @@ impl<'a> InferenceContext<'a> {
         // details of coercion errors though, so I think it's useful to leave
         // the structure like it is.
 
-        let snapshot = self.table.snapshot();
+        let snapshot = self.snapshot();
 
-        let mut autoderef = Autoderef::new(&mut self.table, from_ty.clone());
+        let mut autoderef = Autoderef::new(self, from_ty.clone());
         let mut first_error = None;
         let mut found = None;
 
@@ -317,7 +333,7 @@ impl<'a> InferenceContext<'a> {
         let InferOk { value: ty, goals } = match found {
             Some(d) => d,
             None => {
-                self.table.rollback_to(snapshot);
+                self.rollback_to(snapshot);
                 let err = first_error.expect("coerce_borrowed_pointer had no error");
                 return Err(err);
             }
@@ -513,7 +529,7 @@ impl<'a> InferenceContext<'a> {
         let coerce_from =
             reborrow.as_ref().map_or_else(|| from_ty.clone(), |(_, adj)| adj.target.clone());
 
-        let krate = self.resolver.krate().unwrap();
+        let krate = self.trait_env.krate;
         let coerce_unsized_trait =
             match self.db.lang_item(krate, SmolStr::new_inline("coerce_unsized")) {
                 Some(LangItemTarget::TraitId(trait_)) => trait_,
@@ -546,7 +562,7 @@ impl<'a> InferenceContext<'a> {
         match solution {
             Solution::Unique(v) => {
                 canonicalized.apply_solution(
-                    &mut self.table,
+                    self,
                     Canonical {
                         binders: v.binders,
                         // FIXME handle constraints
@@ -556,7 +572,7 @@ impl<'a> InferenceContext<'a> {
             }
             Solution::Ambig(Guidance::Definite(subst)) => {
                 // FIXME need to record an obligation here
-                canonicalized.apply_solution(&mut self.table, subst)
+                canonicalized.apply_solution(self, subst)
             }
             // FIXME actually we maybe should also accept unknown guidance here
             _ => return Err(TypeError),

crates/hir_ty/src/infer/expr.rs

@@ -67,7 +67,7 @@ impl<'a> InferenceContext<'a> {
         let ty = self.infer_expr_inner(expr, expected);
         if let Some(target) = expected.only_has_type(&mut self.table) {
             match self.coerce(Some(expr), &ty, &target) {
-                Ok(res) => res.value,
+                Ok(res) => res,
                 Err(_) => {
                     self.result
                         .type_mismatches