Merge rust-lang#11780

11780: feat: Add type mismatch diagnostic r=flodiebold a=flodiebold

This adds a proper diagnostic for type mismatches, turning "Add reference here", "Missing Ok or Some" and "Remove this semicolon" into quickfixes for this single diagnostic.
The diagnostic is marked as experimental when it does not have one of these quickfixes, so it can be turned off with `rust-analyzer.diagnostics.enableExperimental` (or specifically with `rust-analyzer.diagnostics.disabled` of course, the ID is `type-mismatch`).
There will still be some false positives, but I think there shouldn't be too many especially when the Chalk fix lands, and it's still experimental anyway 🙂 
This also fixes type checking for `rustc_legacy_const_generics` just to avoid some errors in tests.

Co-authored-by: Florian Diebold <[email protected]>

Author: bors[bot]

crates/hir/src/diagnostics.rs

@@ -5,7 +5,7 @@
 //! be expressed in terms of hir types themselves.
 use cfg::{CfgExpr, CfgOptions};
 use either::Either;
-use hir_def::{path::ModPath, type_ref::Mutability};
+use hir_def::path::ModPath;
 use hir_expand::{name::Name, HirFileId, InFile};
 use syntax::{ast, AstPtr, SyntaxNodePtr, TextRange};
 
@@ -28,7 +28,6 @@ macro_rules! diagnostics {
 }
 
 diagnostics![
-    AddReferenceHere,
     BreakOutsideOfLoop,
     InactiveCode,
     IncorrectCase,
@@ -38,11 +37,10 @@ diagnostics![
     MismatchedArgCount,
     MissingFields,
     MissingMatchArms,
-    MissingOkOrSomeInTailExpr,
     MissingUnsafe,
     NoSuchField,
-    RemoveThisSemicolon,
     ReplaceFilterMapNextWithFindMap,
+    TypeMismatch,
     UnimplementedBuiltinMacro,
     UnresolvedExternCrate,
     UnresolvedImport,
@@ -147,29 +145,18 @@ pub struct MismatchedArgCount {
     pub found: usize,
 }
 
-#[derive(Debug)]
-pub struct RemoveThisSemicolon {
-    pub expr: InFile<AstPtr<ast::Expr>>,
-}
-
-#[derive(Debug)]
-pub struct MissingOkOrSomeInTailExpr {
-    pub expr: InFile<AstPtr<ast::Expr>>,
-    // `Some` or `Ok` depending on whether the return type is Result or Option
-    pub required: String,
-    pub expected: Type,
-}
-
 #[derive(Debug)]
 pub struct MissingMatchArms {
     pub file: HirFileId,
     pub match_expr: AstPtr<ast::Expr>,
 }
 
 #[derive(Debug)]
-pub struct AddReferenceHere {
+pub struct TypeMismatch {
+    // FIXME: add mismatches in patterns as well
     pub expr: InFile<AstPtr<ast::Expr>>,
-    pub mutability: Mutability,
+    pub expected: Type,
+    pub actual: Type,
 }
 
 pub use hir_ty::diagnostics::IncorrectCase;

crates/hir/src/lib.rs

@@ -58,7 +58,6 @@ use hir_ty::{
     consteval::{
         eval_const, unknown_const_as_generic, ComputedExpr, ConstEvalCtx, ConstEvalError, ConstExt,
     },
-    could_unify,
     diagnostics::BodyValidationDiagnostic,
     method_resolution::{self, TyFingerprint},
     primitive::UintTy,
@@ -85,12 +84,11 @@ use crate::db::{DefDatabase, HirDatabase};
 pub use crate::{
     attrs::{HasAttrs, Namespace},
     diagnostics::{
-        AddReferenceHere, AnyDiagnostic, BreakOutsideOfLoop, InactiveCode, IncorrectCase,
-        InvalidDeriveTarget, MacroError, MalformedDerive, MismatchedArgCount, MissingFields,
-        MissingMatchArms, MissingOkOrSomeInTailExpr, MissingUnsafe, NoSuchField,
-        RemoveThisSemicolon, ReplaceFilterMapNextWithFindMap, UnimplementedBuiltinMacro,
-        UnresolvedExternCrate, UnresolvedImport, UnresolvedMacroCall, UnresolvedModule,
-        UnresolvedProcMacro,
+        AnyDiagnostic, BreakOutsideOfLoop, InactiveCode, IncorrectCase, InvalidDeriveTarget,
+        MacroError, MalformedDerive, MismatchedArgCount, MissingFields, MissingMatchArms,
+        MissingUnsafe, NoSuchField, ReplaceFilterMapNextWithFindMap, TypeMismatch,
+        UnimplementedBuiltinMacro, UnresolvedExternCrate, UnresolvedImport, UnresolvedMacroCall,
+        UnresolvedModule, UnresolvedProcMacro,
     },
     has_source::HasSource,
     semantics::{PathResolution, Semantics, SemanticsScope, TypeInfo},
@@ -1005,6 +1003,24 @@ impl Adt {
         Type::from_def(db, id.module(db.upcast()).krate(), id)
     }
 
+    /// Turns this ADT into a type with the given type parameters. This isn't
+    /// the greatest API, FIXME find a better one.
+    pub fn ty_with_args(self, db: &dyn HirDatabase, args: &[Type]) -> Type {
+        let id = AdtId::from(self);
+        let mut it = args.iter().map(|t| t.ty.clone());
+        let ty = TyBuilder::def_ty(db, id.into())
+            .fill(|x| {
+                let r = it.next().unwrap_or_else(|| TyKind::Error.intern(Interner));
+                match x {
+                    ParamKind::Type => GenericArgData::Ty(r).intern(Interner),
+                    ParamKind::Const(ty) => unknown_const_as_generic(ty.clone()),
+                }
+            })
+            .build();
+        let krate = id.module(db.upcast()).krate();
+        Type::new(db, krate, id, ty)
+    }
+
     pub fn module(self, db: &dyn HirDatabase) -> Module {
         match self {
             Adt::Struct(s) => s.module(db),
@@ -1020,6 +1036,14 @@ impl Adt {
             Adt::Enum(e) => e.name(db),
         }
     }
+
+    pub fn as_enum(&self) -> Option<Enum> {
+        if let Self::Enum(v) = self {
+            Some(*v)
+        } else {
+            None
+        }
+    }
 }
 
 impl HasVisibility for Adt {
@@ -1163,6 +1187,30 @@ impl DefWithBody {
                 }
             }
         }
+        for (expr, mismatch) in infer.expr_type_mismatches() {
+            let expr = match source_map.expr_syntax(expr) {
+                Ok(expr) => expr,
+                Err(SyntheticSyntax) => continue,
+            };
+            acc.push(
+                TypeMismatch {
+                    expr,
+                    expected: Type::new(
+                        db,
+                        krate,
+                        DefWithBodyId::from(self),
+                        mismatch.expected.clone(),
+                    ),
+                    actual: Type::new(
+                        db,
+                        krate,
+                        DefWithBodyId::from(self),
+                        mismatch.actual.clone(),
+                    ),
+                }
+                .into(),
+            );
+        }
 
         for expr in hir_ty::diagnostics::missing_unsafe(db, self.into()) {
             match source_map.expr_syntax(expr) {
@@ -1259,25 +1307,6 @@ impl DefWithBody {
                         Err(SyntheticSyntax) => (),
                     }
                 }
-                BodyValidationDiagnostic::RemoveThisSemicolon { expr } => {
-                    match source_map.expr_syntax(expr) {
-                        Ok(expr) => acc.push(RemoveThisSemicolon { expr }.into()),
-                        Err(SyntheticSyntax) => (),
-                    }
-                }
-                BodyValidationDiagnostic::MissingOkOrSomeInTailExpr { expr, required } => {
-                    match source_map.expr_syntax(expr) {
-                        Ok(expr) => acc.push(
-                            MissingOkOrSomeInTailExpr {
-                                expr,
-                                required,
-                                expected: self.body_type(db),
-                            }
-                            .into(),
-                        ),
-                        Err(SyntheticSyntax) => (),
-                    }
-                }
                 BodyValidationDiagnostic::MissingMatchArms { match_expr } => {
                     match source_map.expr_syntax(match_expr) {
                         Ok(source_ptr) => {
@@ -1299,12 +1328,6 @@ impl DefWithBody {
                         Err(SyntheticSyntax) => (),
                     }
                 }
-                BodyValidationDiagnostic::AddReferenceHere { arg_expr, mutability } => {
-                    match source_map.expr_syntax(arg_expr) {
-                        Ok(expr) => acc.push(AddReferenceHere { expr, mutability }.into()),
-                        Err(SyntheticSyntax) => (),
-                    }
-                }
             }
         }
 
@@ -2618,6 +2641,17 @@ impl Type {
         Type { krate, env: environment, ty }
     }
 
+    pub fn reference(inner: &Type, m: Mutability) -> Type {
+        inner.derived(
+            TyKind::Ref(
+                if m.is_mut() { hir_ty::Mutability::Mut } else { hir_ty::Mutability::Not },
+                hir_ty::static_lifetime(),
+                inner.ty.clone(),
+            )
+            .intern(Interner),
+        )
+    }
+
     fn new(db: &dyn HirDatabase, krate: CrateId, lexical_env: impl HasResolver, ty: Ty) -> Type {
         let resolver = lexical_env.resolver(db.upcast());
         let environment = resolver
@@ -2659,6 +2693,12 @@ impl Type {
         matches!(self.ty.kind(Interner), TyKind::Ref(..))
     }
 
+    pub fn as_reference(&self) -> Option<(Type, Mutability)> {
+        let (ty, _lt, m) = self.ty.as_reference()?;
+        let m = Mutability::from_mutable(matches!(m, hir_ty::Mutability::Mut));
+        Some((self.derived(ty.clone()), m))
+    }
+
     pub fn is_slice(&self) -> bool {
         matches!(self.ty.kind(Interner), TyKind::Slice(..))
     }
@@ -2900,7 +2940,7 @@ impl Type {
         self.autoderef_(db).map(move |ty| self.derived(ty))
     }
 
-    pub fn autoderef_<'a>(&'a self, db: &'a dyn HirDatabase) -> impl Iterator<Item = Ty> + 'a {
+    fn autoderef_<'a>(&'a self, db: &'a dyn HirDatabase) -> impl Iterator<Item = Ty> + 'a {
         // There should be no inference vars in types passed here
         let canonical = hir_ty::replace_errors_with_variables(&self.ty);
         let environment = self.env.clone();
@@ -3238,7 +3278,12 @@ impl Type {
 
     pub fn could_unify_with(&self, db: &dyn HirDatabase, other: &Type) -> bool {
         let tys = hir_ty::replace_errors_with_variables(&(self.ty.clone(), other.ty.clone()));
-        could_unify(db, self.env.clone(), &tys)
+        hir_ty::could_unify(db, self.env.clone(), &tys)
+    }
+
+    pub fn could_coerce_to(&self, db: &dyn HirDatabase, to: &Type) -> bool {
+        let tys = hir_ty::replace_errors_with_variables(&(self.ty.clone(), to.ty.clone()));
+        hir_ty::could_coerce(db, self.env.clone(), &tys)
     }
 }
 

crates/hir_def/src/type_ref.rs

@@ -38,6 +38,22 @@ impl Mutability {
             Mutability::Mut => "mut ",
         }
     }
+
+    /// Returns `true` if the mutability is [`Mut`].
+    ///
+    /// [`Mut`]: Mutability::Mut
+    #[must_use]
+    pub fn is_mut(&self) -> bool {
+        matches!(self, Self::Mut)
+    }
+
+    /// Returns `true` if the mutability is [`Shared`].
+    ///
+    /// [`Shared`]: Mutability::Shared
+    #[must_use]
+    pub fn is_shared(&self) -> bool {
+        matches!(self, Self::Shared)
+    }
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]