Implement `#[derive(From)]`

10 files changed, 530 insertions, 6 deletions

diff --git a/compiler/rustc_builtin_macros/messages.ftl b/compiler/rustc_builtin_macros/messages.ftl
index eb3c40cc593..358c0d3db46 100644
--- a/compiler/rustc_builtin_macros/messages.ftl
+++ b/compiler/rustc_builtin_macros/messages.ftl
@@ -222,6 +222,15 @@ builtin_macros_format_unused_args = multiple unused formatting arguments
 
 builtin_macros_format_use_positional = consider using a positional formatting argument instead
 
+builtin_macros_derive_from_wrong_target = `#[derive(From)]` used on {$kind}
+
+builtin_macros_derive_from_wrong_field_count = `#[derive(From)]` used on a struct with {$multiple_fields ->
+    [true] multiple fields
+    *[false] no fields
+}
+
+builtin_macros_derive_from_usage_note = `#[derive(From)]` can only be used on structs with exactly one field
+
 builtin_macros_multiple_default_attrs = multiple `#[default]` attributes
     .note = only one `#[default]` attribute is needed
     .label = `#[default]` used here
diff --git a/compiler/rustc_builtin_macros/src/deriving/from.rs b/compiler/rustc_builtin_macros/src/deriving/from.rs
index 79fd4caa440..ef0e6ca324a 100644
--- a/compiler/rustc_builtin_macros/src/deriving/from.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/from.rs
@@ -1,13 +1,132 @@
 use rustc_ast as ast;
-use rustc_expand::base::{Annotatable, ExtCtxt};
-use rustc_span::{Span, sym};
+use rustc_ast::{ItemKind, VariantData};
+use rustc_errors::MultiSpan;
+use rustc_expand::base::{Annotatable, DummyResult, ExtCtxt};
+use rustc_span::{Ident, Span, kw, sym};
+use thin_vec::thin_vec;
 
+use crate::deriving::generic::ty::{Bounds, Path, PathKind, Ty};
+use crate::deriving::generic::{
+    BlockOrExpr, FieldlessVariantsStrategy, MethodDef, SubstructureFields, TraitDef,
+    combine_substructure,
+};
+use crate::deriving::pathvec_std;
+use crate::errors;
+
+/// Generate an implementation of the `From` trait, provided that `item`
+/// is a struct or a tuple struct with exactly one field.
 pub(crate) fn expand_deriving_from(
     cx: &ExtCtxt<'_>,
     span: Span,
     mitem: &ast::MetaItem,
-    item: &Annotatable,
+    annotatable: &Annotatable,
     push: &mut dyn FnMut(Annotatable),
     is_const: bool,
 ) {
+    let Annotatable::Item(item) = &annotatable else {
+        cx.dcx().bug("derive(From) used on something else than an item");
+    };
+
+    // #[derive(From)] is currently usable only on structs with exactly one field.
+    let field = if let ItemKind::Struct(_, _, data) = &item.kind
+        && let [field] = data.fields()
+    {
+        Some(field.clone())
+    } else {
+        None
+    };
+
+    let from_type = match &field {
+        Some(field) => Ty::AstTy(field.ty.clone()),
+        // We don't have a type to put into From<...> if we don't have a single field, so just put
+        // unit there.
+        None => Ty::Unit,
+    };
+    let path =
+        Path::new_(pathvec_std!(convert::From), vec![Box::new(from_type.clone())], PathKind::Std);
+
+    // Generate code like this:
+    //
+    // struct S(u32);
+    // #[automatically_derived]
+    // impl ::core::convert::From<u32> for S {
+    //     #[inline]
+    //     fn from(value: u32) -> S {
+    //         Self(value)
+    //     }
+    // }
+    let from_trait_def = TraitDef {
+        span,
+        path,
+        skip_path_as_bound: true,
+        needs_copy_as_bound_if_packed: false,
+        additional_bounds: Vec::new(),
+        supports_unions: false,
+        methods: vec![MethodDef {
+            name: sym::from,
+            generics: Bounds { bounds: vec![] },
+            explicit_self: false,
+            nonself_args: vec![(from_type, sym::value)],
+            ret_ty: Ty::Self_,
+            attributes: thin_vec![cx.attr_word(sym::inline, span)],
+            fieldless_variants_strategy: FieldlessVariantsStrategy::Default,
+            combine_substructure: combine_substructure(Box::new(|cx, span, substructure| {
+                let Some(field) = &field else {
+                    let item_span = item.kind.ident().map(|ident| ident.span).unwrap_or(item.span);
+                    let err_span = MultiSpan::from_spans(vec![span, item_span]);
+                    let error = match &item.kind {
+                        ItemKind::Struct(_, _, data) => {
+                            cx.dcx().emit_err(errors::DeriveFromWrongFieldCount {
+                                span: err_span,
+                                multiple_fields: data.fields().len() > 1,
+                            })
+                        }
+                        ItemKind::Enum(_, _, _) | ItemKind::Union(_, _, _) => {
+                            cx.dcx().emit_err(errors::DeriveFromWrongTarget {
+                                span: err_span,
+                                kind: &format!("{} {}", item.kind.article(), item.kind.descr()),
+                            })
+                        }
+                        _ => cx.dcx().bug("Invalid derive(From) ADT input"),
+                    };
+
+                    return BlockOrExpr::new_expr(DummyResult::raw_expr(span, Some(error)));
+                };
+
+                let self_kw = Ident::new(kw::SelfUpper, span);
+                let expr: Box<ast::Expr> = match substructure.fields {
+                    SubstructureFields::StaticStruct(variant, _) => match variant {
+                        // Self {
+                        //     field: value
+                        // }
+                        VariantData::Struct { .. } => cx.expr_struct_ident(
+                            span,
+                            self_kw,
+                            thin_vec![cx.field_imm(
+                                span,
+                                field.ident.unwrap(),
+                                cx.expr_ident(span, Ident::new(sym::value, span))
+                            )],
+                        ),
+                        // Self(value)
+                        VariantData::Tuple(_, _) => cx.expr_call_ident(
+                            span,
+                            self_kw,
+                            thin_vec![cx.expr_ident(span, Ident::new(sym::value, span))],
+                        ),
+                        variant => {
+                            cx.dcx().bug(format!("Invalid derive(From) ADT variant: {variant:?}"));
+                        }
+                    },
+                    _ => cx.dcx().bug("Invalid derive(From) ADT input"),
+                };
+                BlockOrExpr::new_expr(expr)
+            })),
+        }],
+        associated_types: Vec::new(),
+        is_const,
+        is_staged_api_crate: cx.ecfg.features.staged_api(),
+    };
+
+    from_trait_def.expand(cx, mitem, annotatable, push);
 }
diff --git a/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs b/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs
index 00e70b21cf4..1458553d492 100644
--- a/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/generic/ty.rs
@@ -2,7 +2,7 @@
 //! when specifying impls to be derived.
 
 pub(crate) use Ty::*;
-use rustc_ast::{self as ast, Expr, GenericArg, GenericParamKind, Generics, SelfKind};
+use rustc_ast::{self as ast, Expr, GenericArg, GenericParamKind, Generics, SelfKind, TyKind};
 use rustc_expand::base::ExtCtxt;
 use rustc_span::source_map::respan;
 use rustc_span::{DUMMY_SP, Ident, Span, Symbol, kw};
@@ -65,7 +65,7 @@ impl Path {
     }
 }
 
-/// A type. Supports pointers, Self, and literals.
+/// A type. Supports pointers, Self, literals, unit or an arbitrary AST path.
 #[derive(Clone)]
 pub(crate) enum Ty {
     Self_,
@@ -76,6 +76,8 @@ pub(crate) enum Ty {
     Path(Path),
     /// For () return types.
     Unit,
+    /// An arbitrary type.
+    AstTy(Box<ast::Ty>),
 }
 
 pub(crate) fn self_ref() -> Ty {
@@ -101,6 +103,7 @@ impl Ty {
                 let ty = ast::TyKind::Tup(ThinVec::new());
                 cx.ty(span, ty)
             }
+            AstTy(ty) => ty.clone(),
         }
     }
 
@@ -132,6 +135,10 @@ impl Ty {
                 cx.path_all(span, false, vec![self_ty], params)
             }
             Path(p) => p.to_path(cx, span, self_ty, generics),
+            AstTy(ty) => match &ty.kind {
+                TyKind::Path(_, path) => path.clone(),
+                _ => cx.dcx().span_bug(span, "non-path in a path in generic `derive`"),
+            },
             Ref(..) => cx.dcx().span_bug(span, "ref in a path in generic `derive`"),
             Unit => cx.dcx().span_bug(span, "unit in a path in generic `derive`"),
         }
diff --git a/compiler/rustc_builtin_macros/src/errors.rs b/compiler/rustc_builtin_macros/src/errors.rs
index bb520db75b9..54e8f750337 100644
--- a/compiler/rustc_builtin_macros/src/errors.rs
+++ b/compiler/rustc_builtin_macros/src/errors.rs
@@ -447,6 +447,24 @@ pub(crate) struct DefaultHasArg {
 }
 
 #[derive(Diagnostic)]
+#[diag(builtin_macros_derive_from_wrong_target)]
+#[note(builtin_macros_derive_from_usage_note)]
+pub(crate) struct DeriveFromWrongTarget<'a> {
+    #[primary_span]
+    pub(crate) span: MultiSpan,
+    pub(crate) kind: &'a str,
+}
+
+#[derive(Diagnostic)]
+#[diag(builtin_macros_derive_from_wrong_field_count)]
+#[note(builtin_macros_derive_from_usage_note)]
+pub(crate) struct DeriveFromWrongFieldCount {
+    #[primary_span]
+    pub(crate) span: MultiSpan,
+    pub(crate) multiple_fields: bool,
+}
+
+#[derive(Diagnostic)]
 #[diag(builtin_macros_derive_macro_call)]
 pub(crate) struct DeriveMacroCall {
     #[primary_span]
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 16db57da86e..153a5803bf3 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -392,6 +392,7 @@ symbols! {
         __D,
         __H,
         __S,
+        __T,
         __awaitee,
         __try_var,
         _t,
@@ -745,6 +746,7 @@ symbols! {
         contracts_ensures,
         contracts_internals,
         contracts_requires,
+        convert,
         convert_identity,
         copy,
         copy_closures,
@@ -2331,6 +2333,7 @@ symbols! {
         va_start,
         val,
         validity,
+        value,
         values,
         var,
         variant_count,
diff --git a/tests/ui/deriving/deriving-all-codegen.rs b/tests/ui/deriving/deriving-all-codegen.rs
index e2b6804fbd1..00a269ccb5c 100644
--- a/tests/ui/deriving/deriving-all-codegen.rs
+++ b/tests/ui/deriving/deriving-all-codegen.rs
@@ -16,6 +16,7 @@
 #![crate_type = "lib"]
 #![allow(dead_code)]
 #![allow(deprecated)]
+#![feature(derive_from)]
 
 // Empty struct.
 #[derive(Clone, Copy, Debug, Default, Hash, PartialEq, Eq, PartialOrd, Ord)]
@@ -38,6 +39,14 @@ struct PackedPoint {
     y: u32,
 }
 
+#[derive(Clone, Copy, Debug, Default, From, Hash, PartialEq, Eq, PartialOrd, Ord)]
+struct TupleSingleField(u32);
+
+#[derive(Clone, Copy, Debug, Default, From, Hash, PartialEq, Eq, PartialOrd, Ord)]
+struct SingleField {
+    foo: bool,
+}
+
 // A large struct. Note: because this derives `Copy`, it gets the simple
 // `clone` implemention that just does `*self`.
 #[derive(Clone, Copy, Debug, Default, Hash, PartialEq, Eq, PartialOrd, Ord)]
@@ -86,7 +95,7 @@ struct PackedManualCopy(u32);
 impl Copy for PackedManualCopy {}
 
 // A struct with an unsized field. Some derives are not usable in this case.
-#[derive(Debug, Hash, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(Debug, From, Hash, PartialEq, Eq, PartialOrd, Ord)]
 struct Unsized([u32]);
 
 trait Trait {
diff --git a/tests/ui/deriving/deriving-all-codegen.stdout b/tests/ui/deriving/deriving-all-codegen.stdout
index 0e4bfa30257..78b93f39b9e 100644
--- a/tests/ui/deriving/deriving-all-codegen.stdout
+++ b/tests/ui/deriving/deriving-all-codegen.stdout
@@ -17,6 +17,7 @@
 #![crate_type = "lib"]
 #![allow(dead_code)]
 #![allow(deprecated)]
+#![feature(derive_from)]
 #[macro_use]
 extern crate std;
 #[prelude_import]
@@ -249,6 +250,148 @@ impl ::core::cmp::Ord for PackedPoint {
     }
 }
 
+struct TupleSingleField(u32);
+#[automatically_derived]
+impl ::core::clone::Clone for TupleSingleField {
+    #[inline]
+    fn clone(&self) -> TupleSingleField {
+        let _: ::core::clone::AssertParamIsClone<u32>;
+        *self
+    }
+}
+#[automatically_derived]
+impl ::core::marker::Copy for TupleSingleField { }
+#[automatically_derived]
+impl ::core::fmt::Debug for TupleSingleField {
+    #[inline]
+    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+        ::core::fmt::Formatter::debug_tuple_field1_finish(f,
+            "TupleSingleField", &&self.0)
+    }
+}
+#[automatically_derived]
+impl ::core::default::Default for TupleSingleField {
+    #[inline]
+    fn default() -> TupleSingleField {
+        TupleSingleField(::core::default::Default::default())
+    }
+}
+#[automatically_derived]
+impl ::core::convert::From<u32> for TupleSingleField {
+    #[inline]
+    fn from(value: u32) -> TupleSingleField { Self(value) }
+}
+#[automatically_derived]
+impl ::core::hash::Hash for TupleSingleField {
+    #[inline]
+    fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
+        ::core::hash::Hash::hash(&self.0, state)
+    }
+}
+#[automatically_derived]
+impl ::core::marker::StructuralPartialEq for TupleSingleField { }
+#[automatically_derived]
+impl ::core::cmp::PartialEq for TupleSingleField {
+    #[inline]
+    fn eq(&self, other: &TupleSingleField) -> bool { self.0 == other.0 }
+}
+#[automatically_derived]
+impl ::core::cmp::Eq for TupleSingleField {
+    #[inline]
+    #[doc(hidden)]
+    #[coverage(off)]
+    fn assert_receiver_is_total_eq(&self) -> () {
+        let _: ::core::cmp::AssertParamIsEq<u32>;
+    }
+}
+#[automatically_derived]
+impl ::core::cmp::PartialOrd for TupleSingleField {
+    #[inline]
+    fn partial_cmp(&self, other: &TupleSingleField)
+        -> ::core::option::Option<::core::cmp::Ordering> {
+        ::core::cmp::PartialOrd::partial_cmp(&self.0, &other.0)
+    }
+}
+#[automatically_derived]
+impl ::core::cmp::Ord for TupleSingleField {
+    #[inline]
+    fn cmp(&self, other: &TupleSingleField) -> ::core::cmp::Ordering {
+        ::core::cmp::Ord::cmp(&self.0, &other.0)
+    }
+}
+
+struct SingleField {
+    foo: bool,
+}
+#[automatically_derived]
+impl ::core::clone::Clone for SingleField {
+    #[inline]
+    fn clone(&self) -> SingleField {
+        let _: ::core::clone::AssertParamIsClone<bool>;
+        *self
+    }
+}
+#[automatically_derived]
+impl ::core::marker::Copy for SingleField { }
+#[automatically_derived]
+impl ::core::fmt::Debug for SingleField {
+    #[inline]
+    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
+        ::core::fmt::Formatter::debug_struct_field1_finish(f, "SingleField",
+            "foo", &&self.foo)
+    }
+}
+#[automatically_derived]
+impl ::core::default::Default for SingleField {
+    #[inline]
+    fn default() -> SingleField {
+        SingleField { foo: ::core::default::Default::default() }
+    }
+}
+#[automatically_derived]
+impl ::core::convert::From<bool> for SingleField {
+    #[inline]
+    fn from(value: bool) -> SingleField { Self { foo: value } }
+}
+#[automatically_derived]
+impl ::core::hash::Hash for SingleField {
+    #[inline]
+    fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
+        ::core::hash::Hash::hash(&self.foo, state)
+    }
+}
+#[automatically_derived]
+impl ::core::marker::StructuralPartialEq for SingleField { }
+#[automatically_derived]
+impl ::core::cmp::PartialEq for SingleField {
+    #[inline]
+    fn eq(&self, other: &SingleField) -> bool { self.foo == other.foo }
+}
+#[automatically_derived]
+impl ::core::cmp::Eq for SingleField {
+    #[inline]
+    #[doc(hidden)]
+    #[coverage(off)]
+    fn assert_receiver_is_total_eq(&self) -> () {
+        let _: ::core::cmp::AssertParamIsEq<bool>;
+    }
+}
+#[automatically_derived]
+impl ::core::cmp::PartialOrd for SingleField {
+    #[inline]
+    fn partial_cmp(&self, other: &SingleField)
+        -> ::core::option::Option<::core::cmp::Ordering> {
+        ::core::cmp::PartialOrd::partial_cmp(&self.foo, &other.foo)
+    }
+}
+#[automatically_derived]
+impl ::core::cmp::Ord for SingleField {
+    #[inline]
+    fn cmp(&self, other: &SingleField) -> ::core::cmp::Ordering {
+        ::core::cmp::Ord::cmp(&self.foo, &other.foo)
+    }
+}
+
 // A large struct. Note: because this derives `Copy`, it gets the simple
 // `clone` implemention that just does `*self`.
 struct Big {
@@ -572,6 +715,11 @@ impl ::core::fmt::Debug for Unsized {
     }
 }
 #[automatically_derived]
+impl ::core::convert::From<[u32]> for Unsized {
+    #[inline]
+    fn from(value: [u32]) -> Unsized { Self(value) }
+}
+#[automatically_derived]
 impl ::core::hash::Hash for Unsized {
     #[inline]
     fn hash<__H: ::core::hash::Hasher>(&self, state: &mut __H) -> () {
diff --git a/tests/ui/deriving/deriving-from-wrong-target.rs b/tests/ui/deriving/deriving-from-wrong-target.rs
new file mode 100644
index 00000000000..57e009cae69
--- /dev/null
+++ b/tests/ui/deriving/deriving-from-wrong-target.rs
@@ -0,0 +1,38 @@
+//@ edition: 2021
+//@ check-fail
+
+#![feature(derive_from)]
+#![allow(dead_code)]
+
+#[derive(From)]
+//~^ ERROR `#[derive(From)]` used on a struct with no fields
+struct S1;
+
+#[derive(From)]
+//~^ ERROR `#[derive(From)]` used on a struct with no fields
+struct S2 {}
+
+#[derive(From)]
+//~^ ERROR `#[derive(From)]` used on a struct with multiple fields
+struct S3(u32, bool);
+
+#[derive(From)]
+//~^ ERROR `#[derive(From)]` used on a struct with multiple fields
+struct S4 {
+    a: u32,
+    b: bool,
+}
+
+#[derive(From)]
+//~^ ERROR `#[derive(From)]` used on an enum
+enum E1 {}
+
+#[derive(From)]
+//~^ ERROR the size for values of type `T` cannot be known at compilation time [E0277]
+//~| ERROR the size for values of type `T` cannot be known at compilation time [E0277]
+struct SUnsizedField<T: ?Sized> {
+    last: T,
+    //~^ ERROR the size for values of type `T` cannot be known at compilation time [E0277]
+}
+
+fn main() {}
diff --git a/tests/ui/deriving/deriving-from-wrong-target.stderr b/tests/ui/deriving/deriving-from-wrong-target.stderr
new file mode 100644
index 00000000000..13593c95973
--- /dev/null
+++ b/tests/ui/deriving/deriving-from-wrong-target.stderr
@@ -0,0 +1,115 @@
+error: `#[derive(From)]` used on a struct with no fields
+  --> $DIR/deriving-from-wrong-target.rs:7:10
+   |
+LL | #[derive(From)]
+   |          ^^^^
+LL |
+LL | struct S1;
+   |        ^^
+   |
+   = note: `#[derive(From)]` can only be used on structs with exactly one field
+
+error: `#[derive(From)]` used on a struct with no fields
+  --> $DIR/deriving-from-wrong-target.rs:11:10
+   |
+LL | #[derive(From)]
+   |          ^^^^
+LL |
+LL | struct S2 {}
+   |        ^^
+   |
+   = note: `#[derive(From)]` can only be used on structs with exactly one field
+
+error: `#[derive(From)]` used on a struct with multiple fields
+  --> $DIR/deriving-from-wrong-target.rs:15:10
+   |
+LL | #[derive(From)]
+   |          ^^^^
+LL |
+LL | struct S3(u32, bool);
+   |        ^^
+   |
+   = note: `#[derive(From)]` can only be used on structs with exactly one field
+
+error: `#[derive(From)]` used on a struct with multiple fields
+  --> $DIR/deriving-from-wrong-target.rs:19:10
+   |
+LL | #[derive(From)]
+   |          ^^^^
+LL |
+LL | struct S4 {
+   |        ^^
+   |
+   = note: `#[derive(From)]` can only be used on structs with exactly one field
+
+error: `#[derive(From)]` used on an enum
+  --> $DIR/deriving-from-wrong-target.rs:26:10
+   |
+LL | #[derive(From)]
+   |          ^^^^
+LL |
+LL | enum E1 {}
+   |      ^^
+   |
+   = note: `#[derive(From)]` can only be used on structs with exactly one field
+
+error[E0277]: the size for values of type `T` cannot be known at compilation time
+  --> $DIR/deriving-from-wrong-target.rs:30:10
+   |
+LL | #[derive(From)]
+   |          ^^^^ doesn't have a size known at compile-time
+...
+LL | struct SUnsizedField<T: ?Sized> {
+   |                      - this type parameter needs to be `Sized`
+   |
+note: required by an implicit `Sized` bound in `From`
+  --> $SRC_DIR/core/src/convert/mod.rs:LL:COL
+help: consider removing the `?Sized` bound to make the type parameter `Sized`
+   |
+LL - struct SUnsizedField<T: ?Sized> {
+LL + struct SUnsizedField<T> {
+   |
+
+error[E0277]: the size for values of type `T` cannot be known at compilation time
+  --> $DIR/deriving-from-wrong-target.rs:30:10
+   |
+LL | #[derive(From)]
+   |          ^^^^ doesn't have a size known at compile-time
+...
+LL | struct SUnsizedField<T: ?Sized> {
+   |                      - this type parameter needs to be `Sized`
+   |
+note: required because it appears within the type `SUnsizedField<T>`
+  --> $DIR/deriving-from-wrong-target.rs:33:8
+   |
+LL | struct SUnsizedField<T: ?Sized> {
+   |        ^^^^^^^^^^^^^
+   = note: the return type of a function must have a statically known size
+help: consider removing the `?Sized` bound to make the type parameter `Sized`
+   |
+LL - struct SUnsizedField<T: ?Sized> {
+LL + struct SUnsizedField<T> {
+   |
+
+error[E0277]: the size for values of type `T` cannot be known at compilation time
+  --> $DIR/deriving-from-wrong-target.rs:34:11
+   |
+LL | struct SUnsizedField<T: ?Sized> {
+   |                      - this type parameter needs to be `Sized`
+LL |     last: T,
+   |           ^ doesn't have a size known at compile-time
+   |
+   = help: unsized fn params are gated as an unstable feature
+help: consider removing the `?Sized` bound to make the type parameter `Sized`
+   |
+LL - struct SUnsizedField<T: ?Sized> {
+LL + struct SUnsizedField<T> {
+   |
+help: function arguments must have a statically known size, borrowed types always have a known size
+   |
+LL |     last: &T,
+   |           +
+
+error: aborting due to 8 previous errors
+
+For more information about this error, try `rustc --explain E0277`.
diff --git a/tests/ui/deriving/deriving-from.rs b/tests/ui/deriving/deriving-from.rs
new file mode 100644
index 00000000000..ff4c5b4c426
--- /dev/null
+++ b/tests/ui/deriving/deriving-from.rs
@@ -0,0 +1,58 @@
+//@ edition: 2021
+//@ run-pass
+
+#![feature(derive_from)]
+
+#[derive(From)]
+struct TupleSimple(u32);
+
+#[derive(From)]
+struct TupleNonPathType([u32; 4]);
+
+#[derive(From)]
+struct TupleWithRef<'a, T>(&'a T);
+
+#[derive(From)]
+struct TupleSWithBound<T: std::fmt::Debug>(T);
+
+#[derive(From)]
+struct RawIdentifier {
+    r#use: u32,
+}
+
+#[derive(From)]
+struct Field {
+    foo: bool,
+}
+
+#[derive(From)]
+struct Const<const C: usize> {
+    foo: [u32; C],
+}
+
+fn main() {
+    let a = 42u32;
+    let b: [u32; 4] = [0, 1, 2, 3];
+    let c = true;
+
+    let s1: TupleSimple = a.into();
+    assert_eq!(s1.0, a);
+
+    let s2: TupleNonPathType = b.into();
+    assert_eq!(s2.0, b);
+
+    let s3: TupleWithRef<u32> = (&a).into();
+    assert_eq!(s3.0, &a);
+
+    let s4: TupleSWithBound<u32> = a.into();
+    assert_eq!(s4.0, a);
+
+    let s5: RawIdentifier = a.into();
+    assert_eq!(s5.r#use, a);
+
+    let s6: Field = c.into();
+    assert_eq!(s6.foo, c);
+
+    let s7: Const<4> = b.into();
+    assert_eq!(s7.foo, b);
+}