Resolve more

compiler/rustc_hir_typeck/src/_match.rs

@@ -86,7 +86,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let arm_ty = self.check_expr_with_expectation(arm.body, expected);
             all_arms_diverge &= self.diverges.get();
             let tail_defines_return_position_impl_trait =
-                self.return_position_impl_trait_from_match_expectation(orig_expected);
+                self.return_position_impl_trait_from_match_expectation(orig_expected, expr.span);
 
             let (arm_block_id, arm_span) = if let hir::ExprKind::Block(blk, _) = arm.body.kind {
                 (Some(blk.hir_id), self.find_block_span(blk))
@@ -586,8 +586,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     pub(crate) fn return_position_impl_trait_from_match_expectation(
         &self,
         expectation: Expectation<'tcx>,
+        span: Span,
     ) -> Option<LocalDefId> {
-        let expected_ty = expectation.to_option(self)?;
+        let expected_ty = expectation.structurally_resolve(self, span)?;
         let (def_id, args) = match *expected_ty.kind() {
             // FIXME: Could also check that the RPIT is not defined
             ty::Alias(ty::Opaque, alias_ty) => (alias_ty.def_id.as_local()?, alias_ty.args),

compiler/rustc_hir_typeck/src/callee.rs

@@ -573,7 +573,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // We didn't record the in scope traits during late resolution
                 // so we need to probe AllTraits unfortunately
                 ProbeScope::AllTraits,
-                expected.only_has_type(self),
+                expected.structurally_resolve_hard_expectation(self, call_expr.span),
             ) else {
                 return;
             };

compiler/rustc_hir_typeck/src/closure.rs

@@ -57,11 +57,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // It's always helpful for inference if we know the kind of
         // closure sooner rather than later, so first examine the expected
         // type, and see if can glean a closure kind from there.
-        let (expected_sig, expected_kind) = match expected.to_option(self) {
-            Some(ty) => self.deduce_closure_signature(
-                self.try_structurally_resolve_type(expr_span, ty),
-                closure.kind,
-            ),
+        let (expected_sig, expected_kind) = match expected.structurally_resolve(self, expr_span) {
+            Some(ty) => self.deduce_closure_signature(ty, closure.kind),
             None => (None, None),
         };
 

compiler/rustc_hir_typeck/src/expectation.rs

@@ -81,39 +81,31 @@ impl<'a, 'tcx> Expectation<'tcx> {
         }
     }
 
-    /// Resolves `expected` by a single level if it is a variable. If
-    /// there is no expected type or resolution is not possible (e.g.,
-    /// no constraints yet present), just returns `self`.
-    fn resolve(self, fcx: &FnCtxt<'a, 'tcx>) -> Expectation<'tcx> {
+    pub(super) fn structurally_resolve(
+        self,
+        fcx: &FnCtxt<'a, 'tcx>,
+        span: Span,
+    ) -> Option<Ty<'tcx>> {
         match self {
-            NoExpectation => NoExpectation,
-            ExpectCastableToType(t) => ExpectCastableToType(fcx.resolve_vars_if_possible(t)),
-            ExpectHasType(t) => ExpectHasType(fcx.resolve_vars_if_possible(t)),
-            ExpectRvalueLikeUnsized(t) => ExpectRvalueLikeUnsized(fcx.resolve_vars_if_possible(t)),
-        }
-    }
-
-    pub(super) fn to_option(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
-        match self.resolve(fcx) {
             NoExpectation => None,
-            ExpectCastableToType(ty) | ExpectHasType(ty) | ExpectRvalueLikeUnsized(ty) => Some(ty),
+            ExpectCastableToType(ty) | ExpectHasType(ty) | ExpectRvalueLikeUnsized(ty) => {
+                Some(fcx.try_structurally_resolve_type(span, ty))
+            }
         }
     }
 
     /// It sometimes happens that we want to turn an expectation into
     /// a **hard constraint** (i.e., something that must be satisfied
     /// for the program to type-check). `only_has_type` will return
     /// such a constraint, if it exists.
-    pub(super) fn only_has_type(self, fcx: &FnCtxt<'a, 'tcx>) -> Option<Ty<'tcx>> {
+    pub(super) fn structurally_resolve_hard_expectation(
+        self,
+        fcx: &FnCtxt<'a, 'tcx>,
+        span: Span,
+    ) -> Option<Ty<'tcx>> {
         match self {
-            ExpectHasType(ty) => Some(fcx.resolve_vars_if_possible(ty)),
+            ExpectHasType(ty) => Some(fcx.try_structurally_resolve_type(span, ty)),
             NoExpectation | ExpectCastableToType(_) | ExpectRvalueLikeUnsized(_) => None,
         }
     }
-
-    /// Like `only_has_type`, but instead of returning `None` if no
-    /// hard constraint exists, creates a fresh type variable.
-    pub(super) fn coercion_target_type(self, fcx: &FnCtxt<'a, 'tcx>, span: Span) -> Ty<'tcx> {
-        self.only_has_type(fcx).unwrap_or_else(|| fcx.next_ty_var(span))
-    }
 }

compiler/rustc_hir_typeck/src/expr.rs

@@ -624,21 +624,24 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expected: Expectation<'tcx>,
         expr: &'tcx hir::Expr<'tcx>,
     ) -> Ty<'tcx> {
-        let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
-            match ty.kind() {
-                ty::Ref(_, ty, _) | ty::RawPtr(ty, _) => {
-                    if oprnd.is_syntactic_place_expr() {
-                        // Places may legitimately have unsized types.
-                        // For example, dereferences of a wide pointer and
-                        // the last field of a struct can be unsized.
-                        ExpectHasType(*ty)
-                    } else {
-                        Expectation::rvalue_hint(self, *ty)
+        let hint = expected.structurally_resolve_hard_expectation(self, expr.span).map_or(
+            NoExpectation,
+            |ty| {
+                match ty.kind() {
+                    ty::Ref(_, ty, _) | ty::RawPtr(ty, _) => {
+                        if oprnd.is_syntactic_place_expr() {
+                            // Places may legitimately have unsized types.
+                            // For example, dereferences of a wide pointer and
+                            // the last field of a struct can be unsized.
+                            ExpectHasType(*ty)
+                        } else {
+                            Expectation::rvalue_hint(self, *ty)
+                        }
                     }
+                    _ => NoExpectation,
                 }
-                _ => NoExpectation,
-            }
-        });
+            },
+        );
         let ty =
             self.check_expr_with_expectation_and_needs(oprnd, hint, Needs::maybe_mut_place(mutbl));
 
@@ -1301,7 +1304,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // `expected` if it represents a *hard* constraint
         // (`only_has_type`); otherwise, we just go with a
         // fresh type variable.
-        let coerce_to_ty = expected.coercion_target_type(self, sp);
+        let coerce_to_ty = expected
+            .structurally_resolve_hard_expectation(self, sp)
+            .unwrap_or_else(|| self.next_ty_var(sp));
         let mut coerce: DynamicCoerceMany<'_> = CoerceMany::new(coerce_to_ty);
 
         coerce.coerce(self, &self.misc(sp), then_expr, then_ty);
@@ -1311,7 +1316,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let else_diverges = self.diverges.get();
 
             let tail_defines_return_position_impl_trait =
-                self.return_position_impl_trait_from_match_expectation(orig_expected);
+                self.return_position_impl_trait_from_match_expectation(orig_expected, sp);
             let if_cause = self.if_cause(
                 sp,
                 cond_expr.span,
@@ -1351,8 +1356,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         rhs: &'tcx hir::Expr<'tcx>,
         span: Span,
     ) -> Ty<'tcx> {
-        let expected_ty = expected.coercion_target_type(self, expr.span);
-        if expected_ty == self.tcx.types.bool {
+        let expected_ty = expected.structurally_resolve_hard_expectation(self, expr.span);
+        if expected_ty == Some(self.tcx.types.bool) {
             let guar = self.expr_assign_expected_bool_error(expr, lhs, rhs, span);
             return Ty::new_error(self.tcx, guar);
         }
@@ -1518,7 +1523,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let coerce = match source {
             // you can only use break with a value from a normal `loop { }`
             hir::LoopSource::Loop => {
-                let coerce_to = expected.coercion_target_type(self, body.span);
+                let coerce_to = expected
+                    .structurally_resolve_hard_expectation(self, body.span)
+                    .unwrap_or_else(|| self.next_ty_var(body.span));
                 Some(CoerceMany::new(coerce_to))
             }
 
@@ -1635,7 +1642,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> Ty<'tcx> {
         let element_ty = if !args.is_empty() {
             let coerce_to = expected
-                .to_option(self)
+                .structurally_resolve(self, expr.span)
                 .and_then(|uty| match *uty.kind() {
                     ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
                     _ => None,
@@ -1820,13 +1827,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expected: Expectation<'tcx>,
         expr: &'tcx hir::Expr<'tcx>,
     ) -> Ty<'tcx> {
-        let flds = expected.only_has_type(self).and_then(|ty| {
-            let ty = self.try_structurally_resolve_type(expr.span, ty);
-            match ty.kind() {
+        let flds =
+            expected.structurally_resolve_hard_expectation(self, expr.span).and_then(|ty| match ty
+                .kind()
+            {
                 ty::Tuple(flds) => Some(&flds[..]),
                 _ => None,
-            }
-        });
+            });
 
         let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
             Some(fs) if i < fs.len() => {
@@ -1900,17 +1907,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let tcx = self.tcx;
 
         let adt_ty = self.try_structurally_resolve_type(span, adt_ty);
-        let adt_ty_hint = expected.only_has_type(self).and_then(|expected| {
-            self.fudge_inference_if_ok(|| {
-                let ocx = ObligationCtxt::new(self);
-                ocx.sup(&self.misc(span), self.param_env, expected, adt_ty)?;
-                if !ocx.select_where_possible().is_empty() {
-                    return Err(TypeError::Mismatch);
-                }
-                Ok(self.resolve_vars_if_possible(adt_ty))
-            })
-            .ok()
-        });
+        let adt_ty_hint =
+            expected.structurally_resolve_hard_expectation(self, expr.span).and_then(|expected| {
+                self.fudge_inference_if_ok(|| {
+                    let ocx = ObligationCtxt::new(self);
+                    ocx.sup(&self.misc(span), self.param_env, expected, adt_ty)?;
+                    if !ocx.select_where_possible().is_empty() {
+                        return Err(TypeError::Mismatch);
+                    }
+                    Ok(self.resolve_vars_if_possible(adt_ty))
+                })
+                .ok()
+            });
         if let Some(adt_ty_hint) = adt_ty_hint {
             // re-link the variables that the fudging above can create.
             self.demand_eqtype(span, adt_ty_hint, adt_ty);
@@ -2678,7 +2686,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 base_ty,
                 field,
                 did,
-                expected.only_has_type(self),
+                expected.structurally_resolve_hard_expectation(self, expr.span),
             );
             return Ty::new_error(self.tcx(), guar);
         }
@@ -2689,7 +2697,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             field,
             base_ty,
             expr.hir_id,
-            expected.only_has_type(self),
+            expected.structurally_resolve_hard_expectation(self, expr.span),
         ) {
             self.ban_take_value_of_method(expr, base_ty, field)
         } else if !base_ty.is_primitive_ty() {