Revert "feat: Diagnose some incorrect usages of the question mark operator"

crates/hir-expand/src/mod_path.rs

@@ -259,7 +259,6 @@ macro_rules! __known_path {
     (core::future::Future) => {};
     (core::future::IntoFuture) => {};
     (core::ops::Try) => {};
-    (core::ops::FromResidual) => {};
     ($path:path) => {
         compile_error!("Please register your known path in the path module")
     };

crates/hir-expand/src/name.rs

@@ -279,8 +279,6 @@ pub mod known {
         RangeToInclusive,
         RangeTo,
         Range,
-        Residual,
-        FromResidual,
         Neg,
         Not,
         None,

crates/hir-ty/src/infer.rs

@@ -190,9 +190,7 @@ pub(crate) type InferResult<T> = Result<InferOk<T>, TypeError>;
 pub enum InferenceDiagnostic {
     NoSuchField { expr: ExprId },
     BreakOutsideOfLoop { expr: ExprId, is_break: bool },
-    IncorrectTryTarget { expr: ExprId },
     MismatchedArgCount { call_expr: ExprId, expected: usize, found: usize },
-    DoesNotImplement { expr: ExprId, trait_: TraitId, ty: Ty },
 }
 
 /// A mismatch between an expected and an inferred type.
@@ -907,6 +905,17 @@ impl<'a> InferenceContext<'a> {
         self.db.trait_data(trait_).associated_type_by_name(&name![Item])
     }
 
+    fn resolve_ops_try_ok(&self) -> Option<TypeAliasId> {
+        // FIXME resolve via lang_item once try v2 is stable
+        let path = path![core::ops::Try];
+        let trait_ = self.resolver.resolve_known_trait(self.db.upcast(), &path)?;
+        let trait_data = self.db.trait_data(trait_);
+        trait_data
+            // FIXME remove once try v2 is stable
+            .associated_type_by_name(&name![Ok])
+            .or_else(|| trait_data.associated_type_by_name(&name![Output]))
+    }
+
     fn resolve_ops_neg_output(&self) -> Option<TypeAliasId> {
         let trait_ = self.resolve_lang_item(name![neg])?.as_trait()?;
         self.db.trait_data(trait_).associated_type_by_name(&name![Output])

crates/hir-ty/src/infer/expr.rs

@@ -19,24 +19,24 @@ use hir_def::{
     resolver::resolver_for_expr,
     ConstParamId, FieldId, ItemContainerId, Lookup,
 };
-use hir_expand::{name, name::Name};
+use hir_expand::name::Name;
 use stdx::always;
 use syntax::ast::RangeOp;
 
 use crate::{
     autoderef::{self, Autoderef},
     consteval,
-    infer::{coerce::CoerceMany, find_continuable, path, BreakableKind},
+    infer::{coerce::CoerceMany, find_continuable, BreakableKind},
     lower::{
         const_or_path_to_chalk, generic_arg_to_chalk, lower_to_chalk_mutability, ParamLoweringMode,
     },
     mapping::{from_chalk, ToChalk},
     method_resolution::{self, lang_names_for_bin_op, VisibleFromModule},
     primitive::{self, UintTy},
-    static_lifetime, to_assoc_type_id, to_chalk_trait_id,
+    static_lifetime, to_chalk_trait_id,
     utils::{generics, Generics},
-    AdtId, AliasEq, AliasTy, Binders, CallableDefId, FnPointer, FnSig, FnSubst, Interner,
-    ProjectionTy, Rawness, Scalar, Substitution, TraitRef, Ty, TyBuilder, TyExt, TyKind,
+    AdtId, Binders, CallableDefId, FnPointer, FnSig, FnSubst, Interner, Rawness, Scalar,
+    Substitution, TraitRef, Ty, TyBuilder, TyExt, TyKind,
 };
 
 use super::{
@@ -564,29 +564,9 @@ impl<'a> InferenceContext<'a> {
                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
                 self.resolve_associated_type(inner_ty, self.resolve_future_future_output())
             }
-            &Expr::Try { expr } => {
-                let inner_ty = self.infer_expr_inner(expr, &Expectation::none());
-                match self.resolve_try_impl_for(inner_ty.clone()) {
-                    Some((_, Some((output, residual)))) => {
-                        if let Some((_trait, false)) =
-                            self.implements_from_residual(self.return_ty.clone(), residual)
-                        {
-                            self.push_diagnostic(InferenceDiagnostic::IncorrectTryTarget {
-                                expr: tgt_expr,
-                            });
-                        }
-                        output
-                    }
-                    Some((trait_, None)) => {
-                        self.push_diagnostic(InferenceDiagnostic::DoesNotImplement {
-                            expr,
-                            trait_,
-                            ty: inner_ty,
-                        });
-                        self.err_ty()
-                    }
-                    None => self.err_ty(),
-                }
+            Expr::Try { expr } => {
+                let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
+                self.resolve_associated_type(inner_ty, self.resolve_ops_try_ok())
             }
             Expr::Cast { expr, type_ref } => {
                 // FIXME: propagate the "castable to" expectation (and find a test case that shows this is necessary)
@@ -1550,67 +1530,4 @@ impl<'a> InferenceContext<'a> {
         let ctx = self.breakables.pop().expect("breakable stack broken");
         (ctx.may_break.then(|| ctx.coerce.complete()), res)
     }
-
-    /// Check whether `ty` implements `FromResidual<r>`
-    fn implements_from_residual(&mut self, ty: Ty, r: Ty) -> Option<(hir_def::TraitId, bool)> {
-        let from_residual_trait = self
-            .resolver
-            .resolve_known_trait(self.db.upcast(), &(super::path![core::ops::FromResidual]))?;
-        let r = GenericArgData::Ty(r).intern(Interner);
-        let b = TyBuilder::trait_ref(self.db, from_residual_trait);
-        if b.remaining() != 2 {
-            return Some((from_residual_trait, false));
-        }
-        let trait_ref = b.push(ty).push(r).build();
-        Some((from_residual_trait, self.table.try_obligation(trait_ref.cast(Interner)).is_some()))
-    }
-
-    fn resolve_try_impl_for(&mut self, ty: Ty) -> Option<(hir_def::TraitId, Option<(Ty, Ty)>)> {
-        let path = path![core::ops::Try];
-        let trait_ = self.resolver.resolve_known_trait(self.db.upcast(), &path)?;
-
-        let trait_ref = TyBuilder::trait_ref(self.db, trait_).push(ty).build();
-        let substitution = trait_ref.substitution.clone();
-        self.push_obligation(trait_ref.clone().cast(Interner));
-
-        let trait_data = self.db.trait_data(trait_);
-        let output = trait_data.associated_type_by_name(&name![Output]);
-        let residual = trait_data.associated_type_by_name(&name![Residual]);
-
-        let output_ty = match output {
-            Some(output) => {
-                let output_ty = self.table.new_type_var();
-                let alias_eq = AliasEq {
-                    alias: AliasTy::Projection(ProjectionTy {
-                        associated_ty_id: to_assoc_type_id(output),
-                        substitution: substitution.clone(),
-                    }),
-                    ty: output_ty.clone(),
-                };
-                self.push_obligation(alias_eq.cast(Interner));
-                output_ty
-            }
-            None => self.err_ty(),
-        };
-        let residual_ty = match residual {
-            Some(residual) => {
-                let residual_ty = self.table.new_type_var();
-                let alias_eq = AliasEq {
-                    alias: AliasTy::Projection(ProjectionTy {
-                        associated_ty_id: to_assoc_type_id(residual),
-                        substitution,
-                    }),
-                    ty: residual_ty.clone(),
-                };
-                self.push_obligation(alias_eq.cast(Interner));
-                residual_ty
-            }
-            None => self.err_ty(),
-        };
-        // FIXME: We are doing the work twice here I think?
-        Some((
-            trait_,
-            self.table.try_obligation(trait_ref.cast(Interner)).map(|_| (output_ty, residual_ty)),
-        ))
-    }
 }

crates/hir-ty/src/method_resolution.rs

@@ -1111,24 +1111,6 @@ pub fn resolve_indexing_op(
     }
     None
 }
-/// Returns the receiver type for the try branch trait call.
-pub fn resolve_branch_op(
-    db: &dyn HirDatabase,
-    env: Arc<TraitEnvironment>,
-    ty: Canonical<Ty>,
-    try_trait: TraitId,
-) -> Option<ReceiverAdjustments> {
-    let mut table = InferenceTable::new(db, env.clone());
-    let ty = table.instantiate_canonical(ty);
-    let (deref_chain, adj) = autoderef_method_receiver(&mut table, ty);
-    for (ty, adj) in deref_chain.into_iter().zip(adj) {
-        let goal = generic_implements_goal(db, env.clone(), try_trait, &ty);
-        if db.trait_solve(env.krate, goal.cast(Interner)).is_some() {
-            return Some(adj);
-        }
-    }
-    None
-}
 
 macro_rules! check_that {
     ($cond:expr) => {

crates/hir-ty/src/tests/traits.rs

@@ -162,16 +162,98 @@ fn test() {
     );
 }
 
+#[test]
+fn infer_try() {
+    check_types(
+        r#"
+//- /main.rs crate:main deps:core
+fn test() {
+    let r: Result<i32, u64> = Result::Ok(1);
+    let v = r?;
+    v;
+} //^ i32
+
+//- /core.rs crate:core
+pub mod ops {
+    pub trait Try {
+        type Ok;
+        type Error;
+    }
+}
+
+pub mod result {
+    pub enum Result<O, E> {
+        Ok(O),
+        Err(E)
+    }
+
+    impl<O, E> crate::ops::Try for Result<O, E> {
+        type Ok = O;
+        type Error = E;
+    }
+}
+
+pub mod prelude {
+    pub mod rust_2018 {
+        pub use crate::{result::*, ops::*};
+    }
+}
+"#,
+    );
+}
+
 #[test]
 fn infer_try_trait_v2() {
     check_types(
         r#"
-//- minicore: try
-fn test() -> core::ops::ControlFlow<u32, f32> {
-    let r: core::ops::ControlFlow<u32, f32> = core::ops::ControlFlow::Continue(1.0);
+//- /main.rs crate:main deps:core
+fn test() {
+    let r: Result<i32, u64> = Result::Ok(1);
     let v = r?;
-      //^ f32
-    r
+    v;
+} //^ i32
+
+//- /core.rs crate:core
+mod ops {
+    mod try_trait {
+        pub trait Try: FromResidual {
+            type Output;
+            type Residual;
+        }
+        pub trait FromResidual<R = <Self as Try>::Residual> {}
+    }
+
+    pub use self::try_trait::FromResidual;
+    pub use self::try_trait::Try;
+}
+
+mod convert {
+    pub trait From<T> {}
+    impl<T> From<T> for T {}
+}
+
+pub mod result {
+    use crate::convert::From;
+    use crate::ops::{Try, FromResidual};
+
+    pub enum Infallible {}
+    pub enum Result<O, E> {
+        Ok(O),
+        Err(E)
+    }
+
+    impl<O, E> Try for Result<O, E> {
+        type Output = O;
+        type Error = Result<Infallible, E>;
+    }
+
+    impl<T, E, F: From<E>> FromResidual<Result<Infallible, E>> for Result<T, F> {}
+}
+
+pub mod prelude {
+    pub mod rust_2018 {
+        pub use crate::result::*;
+    }
 }
 "#,
     );

crates/hir/src/diagnostics.rs

@@ -6,7 +6,7 @@
 use base_db::CrateId;
 use cfg::{CfgExpr, CfgOptions};
 use either::Either;
-use hir_def::{path::ModPath, TraitId};
+use hir_def::path::ModPath;
 use hir_expand::{name::Name, HirFileId, InFile};
 use syntax::{ast, AstPtr, SyntaxNodePtr, TextRange};
 
@@ -33,15 +33,13 @@ diagnostics![
     BreakOutsideOfLoop,
     InactiveCode,
     IncorrectCase,
-    IncorrectTryExpr,
     InvalidDeriveTarget,
     MacroError,
     MalformedDerive,
     MismatchedArgCount,
     MissingFields,
     MissingMatchArms,
     MissingUnsafe,
-    NotImplemented,
     NoSuchField,
     ReplaceFilterMapNextWithFindMap,
     TypeMismatch,
@@ -155,16 +153,6 @@ pub struct MismatchedArgCount {
     pub expected: usize,
     pub found: usize,
 }
-#[derive(Debug)]
-pub struct IncorrectTryExpr {
-    pub expr: InFile<AstPtr<ast::Expr>>,
-}
-#[derive(Debug)]
-pub struct NotImplemented {
-    pub expr: InFile<AstPtr<ast::Expr>>,
-    pub trait_: TraitId,
-    pub ty: Type,
-}
 
 #[derive(Debug)]
 pub struct MissingMatchArms {