WF-check struct field types at construction site

compiler/rustc_hir_typeck/src/expr.rs

@@ -1736,6 +1736,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 Ty::new_error(tcx, guar)
             };
 
+            // Check that the expected field type is WF. Otherwise, we emit no use-site error
+            // in the case of coercions for non-WF fields, which leads to incorrect error
+            // tainting. See issue #126272.
+            self.register_wf_obligation(
+                field_type.into(),
+                field.expr.span,
+                ObligationCauseCode::WellFormed(None),
+            );
+
             // Make sure to give a type to the field even if there's
             // an error, so we can continue type-checking.
             let ty = self.check_expr_with_hint(field.expr, field_type);

tests/ui/const-generics/adt_const_params/unsizing-wfcheck-issue-126272.rs

@@ -0,0 +1,28 @@
+// This ensures we don't ICE in situations like rust-lang/rust#126272.
+
+#![feature(adt_const_params)]
+#![allow(incomplete_features)]
+
+use std::marker::ConstParamTy;
+
+#[derive(Debug, PartialEq, Eq, ConstParamTy)]
+//~^ ERROR the trait `ConstParamTy_`
+//~| ERROR the trait `ConstParamTy_`
+struct Foo {
+    nested: &'static Bar<dyn std::fmt::Debug>,
+    //~^ ERROR the size for values
+    //~| ERROR the size for values
+    //~| ERROR binary operation `==` cannot
+    //~| ERROR the trait bound `dyn Debug: Eq`
+    //~| ERROR the size for values
+}
+
+#[derive(Debug, PartialEq, Eq, ConstParamTy)]
+struct Bar<T>(T);
+
+struct Test<const F: Foo>;
+
+fn main() {
+    let x: Test<{ Foo { nested: &Bar(4) } }> = Test;
+    //~^ ERROR the size for values
+}

tests/ui/const-generics/adt_const_params/unsizing-wfcheck-issue-126272.stderr

@@ -0,0 +1,160 @@
+error[E0277]: the size for values of type `(dyn Debug + 'static)` cannot be known at compilation time
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:12:13
+   |
+LL |     nested: &'static Bar<dyn std::fmt::Debug>,
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn Debug + 'static)`
+note: required by an implicit `Sized` bound in `Bar`
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:21:12
+   |
+LL | struct Bar<T>(T);
+   |            ^ required by the implicit `Sized` requirement on this type parameter in `Bar`
+help: you could relax the implicit `Sized` bound on `T` if it were used through indirection like `&T` or `Box<T>`
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:21:12
+   |
+LL | struct Bar<T>(T);
+   |            ^  - ...if indirection were used here: `Box<T>`
+   |            |
+   |            this could be changed to `T: ?Sized`...
+
+error[E0204]: the trait `ConstParamTy_` cannot be implemented for this type
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:8:32
+   |
+LL | #[derive(Debug, PartialEq, Eq, ConstParamTy)]
+   |                                ^^^^^^^^^^^^
+...
+LL |     nested: &'static Bar<dyn std::fmt::Debug>,
+   |     ----------------------------------------- this field does not implement `ConstParamTy_`
+   |
+   = note: this error originates in the derive macro `ConstParamTy` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0204]: the trait `ConstParamTy_` cannot be implemented for this type
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:8:32
+   |
+LL | #[derive(Debug, PartialEq, Eq, ConstParamTy)]
+   |                                ^^^^^^^^^^^^
+...
+LL |     nested: &'static Bar<dyn std::fmt::Debug>,
+   |     ----------------------------------------- this field does not implement `ConstParamTy_`
+   |
+note: the `ConstParamTy_` impl for `&'static Bar<(dyn Debug + 'static)>` requires that `(dyn Debug + 'static): Eq`
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:12:13
+   |
+LL |     nested: &'static Bar<dyn std::fmt::Debug>,
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+note: the `ConstParamTy_` impl for `&'static Bar<(dyn Debug + 'static)>` requires that `(dyn Debug + 'static): Sized`
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:12:13
+   |
+LL |     nested: &'static Bar<dyn std::fmt::Debug>,
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+note: the `ConstParamTy_` impl for `&'static Bar<(dyn Debug + 'static)>` requires that `(dyn Debug + 'static): UnsizedConstParamTy`
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:12:13
+   |
+LL |     nested: &'static Bar<dyn std::fmt::Debug>,
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   = note: this error originates in the derive macro `ConstParamTy` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: the size for values of type `(dyn Debug + 'static)` cannot be known at compilation time
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:12:5
+   |
+LL | #[derive(Debug, PartialEq, Eq, ConstParamTy)]
+   |          ----- in this derive macro expansion
+...
+LL |     nested: &'static Bar<dyn std::fmt::Debug>,
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn Debug + 'static)`, which is required by `&&'static Bar<(dyn Debug + 'static)>: Debug`
+   = help: the trait `Debug` is implemented for `Bar<T>`
+note: required for `Bar<(dyn Debug + 'static)>` to implement `Debug`
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:20:10
+   |
+LL | #[derive(Debug, PartialEq, Eq, ConstParamTy)]
+   |          ^^^^^
+LL | struct Bar<T>(T);
+   |            - unsatisfied trait bound introduced in this `derive` macro
+   = note: 2 redundant requirements hidden
+   = note: required for `&&'static Bar<(dyn Debug + 'static)>` to implement `Debug`
+   = note: required for the cast from `&&&'static Bar<(dyn Debug + 'static)>` to `&dyn Debug`
+   = note: this error originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0369]: binary operation `==` cannot be applied to type `&Bar<dyn Debug>`
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:12:5
+   |
+LL | #[derive(Debug, PartialEq, Eq, ConstParamTy)]
+   |                 --------- in this derive macro expansion
+...
+LL |     nested: &'static Bar<dyn std::fmt::Debug>,
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: this error originates in the derive macro `PartialEq` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: the trait bound `dyn Debug: Eq` is not satisfied
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:12:5
+   |
+LL | #[derive(Debug, PartialEq, Eq, ConstParamTy)]
+   |                            -- in this derive macro expansion
+...
+LL |     nested: &'static Bar<dyn std::fmt::Debug>,
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Eq` is not implemented for `dyn Debug`, which is required by `&'static Bar<dyn Debug>: Eq`
+   |
+   = help: the trait `Eq` is implemented for `Bar<T>`
+note: required for `Bar<dyn Debug>` to implement `Eq`
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:20:28
+   |
+LL | #[derive(Debug, PartialEq, Eq, ConstParamTy)]
+   |                            ^^ unsatisfied trait bound introduced in this `derive` macro
+   = note: 1 redundant requirement hidden
+   = note: required for `&'static Bar<dyn Debug>` to implement `Eq`
+note: required by a bound in `AssertParamIsEq`
+  --> $SRC_DIR/core/src/cmp.rs:LL:COL
+   = note: this error originates in the derive macro `Eq` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: the size for values of type `dyn Debug` cannot be known at compilation time
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:12:5
+   |
+LL | #[derive(Debug, PartialEq, Eq, ConstParamTy)]
+   |                            -- in this derive macro expansion
+...
+LL |     nested: &'static Bar<dyn std::fmt::Debug>,
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `dyn Debug`
+note: required by an implicit `Sized` bound in `Bar`
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:21:12
+   |
+LL | struct Bar<T>(T);
+   |            ^ required by the implicit `Sized` requirement on this type parameter in `Bar`
+help: you could relax the implicit `Sized` bound on `T` if it were used through indirection like `&T` or `Box<T>`
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:21:12
+   |
+LL | struct Bar<T>(T);
+   |            ^  - ...if indirection were used here: `Box<T>`
+   |            |
+   |            this could be changed to `T: ?Sized`...
+   = note: this error originates in the derive macro `Eq` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error[E0277]: the size for values of type `(dyn Debug + 'static)` cannot be known at compilation time
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:26:33
+   |
+LL |     let x: Test<{ Foo { nested: &Bar(4) } }> = Test;
+   |                                 ^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn Debug + 'static)`
+note: required by an implicit `Sized` bound in `Bar`
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:21:12
+   |
+LL | struct Bar<T>(T);
+   |            ^ required by the implicit `Sized` requirement on this type parameter in `Bar`
+help: you could relax the implicit `Sized` bound on `T` if it were used through indirection like `&T` or `Box<T>`
+  --> $DIR/unsizing-wfcheck-issue-126272.rs:21:12
+   |
+LL | struct Bar<T>(T);
+   |            ^  - ...if indirection were used here: `Box<T>`
+   |            |
+   |            this could be changed to `T: ?Sized`...
+
+error: aborting due to 8 previous errors
+
+Some errors have detailed explanations: E0204, E0277, E0369.
+For more information about an error, try `rustc --explain E0204`.

tests/ui/const-generics/generic_const_exprs/no_where_clause.rs

@@ -17,6 +17,7 @@ impl<const N: usize> Example<N> {
       a: [0.; N],
       b: [0.; complex_maths(N)],
       //~^ ERROR: unconstrained generic constant
+      //~| ERROR: unconstrained generic constant
     }
   }
 }

tests/ui/const-generics/generic_const_exprs/no_where_clause.stderr

@@ -9,6 +9,17 @@ help: try adding a `where` bound
 LL | pub struct Example<const N: usize> where [(); complex_maths(N)]: {
    |                                    +++++++++++++++++++++++++++++
 
+error: unconstrained generic constant
+  --> $DIR/no_where_clause.rs:18:10
+   |
+LL |       b: [0.; complex_maths(N)],
+   |          ^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: try adding a `where` bound
+   |
+LL |   pub fn new() -> Self where [(); complex_maths(N)]: {
+   |                        +++++++++++++++++++++++++++++
+
 error: unconstrained generic constant
   --> $DIR/no_where_clause.rs:18:15
    |
@@ -20,5 +31,5 @@ help: try adding a `where` bound
 LL |   pub fn new() -> Self where [(); complex_maths(N)]: {
    |                        +++++++++++++++++++++++++++++
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 

tests/ui/generic-associated-types/issue-71176.rs

@@ -16,6 +16,6 @@ struct Holder<B> {
 
 fn main() {
     Holder {
-        inner: Box::new(()),
+        inner: Box::new(()), //~ ERROR: the trait `Provider` cannot be made into an object
     };
 }

tests/ui/generic-associated-types/issue-71176.stderr

@@ -64,7 +64,23 @@ LL |     type A<'a>;
    = help: consider moving `A` to another trait
    = help: only type `()` implements the trait, consider using it directly instead
 
-error: aborting due to 4 previous errors
+error[E0038]: the trait `Provider` cannot be made into an object
+  --> $DIR/issue-71176.rs:19:16
+   |
+LL |         inner: Box::new(()),
+   |                ^^^^^^^^^^^^ `Provider` cannot be made into an object
+   |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/issue-71176.rs:2:10
+   |
+LL | trait Provider {
+   |       -------- this trait cannot be made into an object...
+LL |     type A<'a>;
+   |          ^ ...because it contains the generic associated type `A`
+   = help: consider moving `A` to another trait
+   = help: only type `()` implements the trait, consider using it directly instead
+
+error: aborting due to 5 previous errors
 
 Some errors have detailed explanations: E0038, E0107.
 For more information about an error, try `rustc --explain E0038`.

tests/ui/issues/issue-19380.rs

@@ -15,5 +15,6 @@ struct Bar {
 const FOO : Foo = Foo;
 const BAR : Bar = Bar { foos: &[&FOO]};
 //~^ ERROR E0038
+//~| ERROR E0038
 
 fn main() { }

tests/ui/issues/issue-19380.stderr

@@ -45,6 +45,29 @@ help: alternatively, consider constraining `qiz` so it does not apply to trait o
 LL |   fn qiz() where Self: Sized;
    |            +++++++++++++++++
 
-error: aborting due to 2 previous errors
+error[E0038]: the trait `Qiz` cannot be made into an object
+  --> $DIR/issue-19380.rs:16:31
+   |
+LL | const BAR : Bar = Bar { foos: &[&FOO]};
+   |                               ^^^^^^^ `Qiz` cannot be made into an object
+   |
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+  --> $DIR/issue-19380.rs:2:6
+   |
+LL | trait Qiz {
+   |       --- this trait cannot be made into an object...
+LL |   fn qiz();
+   |      ^^^ ...because associated function `qiz` has no `self` parameter
+   = help: only type `Foo` implements the trait, consider using it directly instead
+help: consider turning `qiz` into a method by giving it a `&self` argument
+   |
+LL |   fn qiz(&self);
+   |          +++++
+help: alternatively, consider constraining `qiz` so it does not apply to trait objects
+   |
+LL |   fn qiz() where Self: Sized;
+   |            +++++++++++++++++
+
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0038`.

tests/ui/statics/unsizing-wfcheck-issue-127299.rs

@@ -0,0 +1,17 @@
+// This ensures we don't ICE in situations like rust-lang/rust#127299.
+
+trait Qux {
+    fn bar() -> i32;
+}
+
+pub struct Lint {
+    pub desc: &'static dyn Qux,
+    //~^ ERROR cannot be made into an object
+}
+
+static FOO: &Lint = &Lint { desc: "desc" };
+//~^ ERROR cannot be shared between threads safely
+//~| ERROR cannot be made into an object
+//~| ERROR cannot be made into an object
+
+fn main() {}