Check that return type is WF in typeck

Without it non-WF types could pass typeck and then
later fail in MIR/const eval

Author: gurry

Diff for: compiler/rustc_hir_typeck/src/lib.rs

@@ -61,7 +61,7 @@ use rustc_hir::{HirIdMap, Node};
 use rustc_hir_analysis::astconv::AstConv;
 use rustc_hir_analysis::check::check_abi;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
-use rustc_infer::traits::ObligationInspector;
+use rustc_infer::traits::{ObligationCauseCode, ObligationInspector, WellFormedLoc};
 use rustc_middle::query::Providers;
 use rustc_middle::traits;
 use rustc_middle::ty::{self, Ty, TyCtxt};
@@ -253,6 +253,10 @@ fn typeck_with_fallback<'tcx>(
         let expected_type = expected_type.unwrap_or_else(fallback);
 
         let expected_type = fcx.normalize(body.value.span, expected_type);
+
+        let wf_code = ObligationCauseCode::WellFormed(Some(WellFormedLoc::Ty(def_id)));
+        fcx.register_wf_obligation(expected_type.into(), body.value.span, wf_code);
+
         fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
 
         // Gather locals in statics (because of block expressions).

Diff for: tests/ui/const-generics/issues/issue-71202.rs

@@ -25,7 +25,7 @@ impl<T: Copy> DataHolder<T> {
         }
 
         <IsCopy<T>>::VALUE
-    } as usize] = [];
+    } as usize] = []; //~ ERROR unconstrained generic constant
 }
 
 fn main() {}

Diff for: tests/ui/const-generics/issues/issue-71202.stderr

@@ -29,5 +29,30 @@ LL | |     } as usize] = [];
                    <IsCopy<T>>::VALUE
                } as usize]:`
 
-error: aborting due to 1 previous error
+error: unconstrained generic constant
+  --> $DIR/issue-71202.rs:28:19
+   |
+LL |     } as usize] = [];
+   |                   ^^
+   |
+   = help: try adding a `where` bound using this expression: `where [(); 1 - {
+                   trait NotCopy {
+                       const VALUE: bool = false;
+                   }
+           
+                   impl<__Type: ?Sized> NotCopy for __Type {}
+           
+                   struct IsCopy<__Type: ?Sized>(PhantomData<__Type>);
+           
+                   impl<__Type> IsCopy<__Type>
+                   where
+                       __Type: Sized + Copy,
+                   {
+                       const VALUE: bool = true;
+                   }
+           
+                   <IsCopy<T>>::VALUE
+               } as usize]:`
+
+error: aborting due to 2 previous errors
 

Diff for: tests/ui/layout/issue-84108.rs

@@ -11,4 +11,5 @@ const BAR: (&Path, [u8], usize) = ("hello", [], 42);
 
 static BAZ: ([u8], usize) = ([], 0);
 //~^ ERROR the size for values of type `[u8]` cannot be known at compilation time
+//~| ERROR the size for values of type `[u8]` cannot be known at compilation time
 //~| ERROR mismatched types

Diff for: tests/ui/layout/issue-84108.stderr

@@ -29,6 +29,16 @@ LL | static BAZ: ([u8], usize) = ([], 0);
    = help: the trait `Sized` is not implemented for `[u8]`
    = note: only the last element of a tuple may have a dynamically sized type
 
+error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
+  --> $DIR/issue-84108.rs:12:13
+   |
+LL | static BAZ: ([u8], usize) = ([], 0);
+   |             ^^^^^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `[u8]`
+   = note: only the last element of a tuple may have a dynamically sized type
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
 error[E0308]: mismatched types
   --> $DIR/issue-84108.rs:12:30
    |
@@ -38,7 +48,7 @@ LL | static BAZ: ([u8], usize) = ([], 0);
    = note: expected slice `[u8]`
               found array `[_; 0]`
 
-error: aborting due to 4 previous errors
+error: aborting due to 5 previous errors
 
 Some errors have detailed explanations: E0277, E0308, E0412.
 For more information about an error, try `rustc --explain E0277`.

Diff for: tests/ui/trait-bounds/ice-unsized-tuple-const-issue-121443.rs

@@ -0,0 +1,16 @@
+// Regression test for #121443
+// Checks that no ICE occurs upon encountering
+// a tuple with unsized element that is not
+// the last element
+
+type Fn = dyn FnOnce() -> u8;
+
+const TEST: Fn = some_fn;
+//~^ ERROR cannot find value `some_fn` in this scope
+//~| ERROR the size for values of type `(dyn FnOnce() -> u8 + 'static)` cannot be known at compilation time
+//~| ERROR the size for values of type `(dyn FnOnce() -> u8 + 'static)` cannot be known at compilation time
+const TEST2: (Fn, u8) = (TEST, 0);
+//~^ ERROR the size for values of type `(dyn FnOnce() -> u8 + 'static)` cannot be known at compilation time
+//~| ERROR the size for values of type `(dyn FnOnce() -> u8 + 'static)` cannot be known at compilation time
+
+fn main() {}

Diff for: tests/ui/trait-bounds/ice-unsized-tuple-const-issue-121443.stderr

@@ -0,0 +1,45 @@
+error[E0425]: cannot find value `some_fn` in this scope
+  --> $DIR/ice-unsized-tuple-const-issue-121443.rs:8:18
+   |
+LL | const TEST: Fn = some_fn;
+   |                  ^^^^^^^ not found in this scope
+
+error[E0277]: the size for values of type `(dyn FnOnce() -> u8 + 'static)` cannot be known at compilation time
+  --> $DIR/ice-unsized-tuple-const-issue-121443.rs:8:13
+   |
+LL | const TEST: Fn = some_fn;
+   |             ^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn FnOnce() -> u8 + 'static)`
+
+error[E0277]: the size for values of type `(dyn FnOnce() -> u8 + 'static)` cannot be known at compilation time
+  --> $DIR/ice-unsized-tuple-const-issue-121443.rs:8:18
+   |
+LL | const TEST: Fn = some_fn;
+   |                  ^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn FnOnce() -> u8 + 'static)`
+   = note: constant expressions must have a statically known size
+
+error[E0277]: the size for values of type `(dyn FnOnce() -> u8 + 'static)` cannot be known at compilation time
+  --> $DIR/ice-unsized-tuple-const-issue-121443.rs:12:14
+   |
+LL | const TEST2: (Fn, u8) = (TEST, 0);
+   |              ^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn FnOnce() -> u8 + 'static)`
+   = note: only the last element of a tuple may have a dynamically sized type
+
+error[E0277]: the size for values of type `(dyn FnOnce() -> u8 + 'static)` cannot be known at compilation time
+  --> $DIR/ice-unsized-tuple-const-issue-121443.rs:12:25
+   |
+LL | const TEST2: (Fn, u8) = (TEST, 0);
+   |                         ^^^^^^^^^ doesn't have a size known at compile-time
+   |
+   = help: the trait `Sized` is not implemented for `(dyn FnOnce() -> u8 + 'static)`
+   = note: only the last element of a tuple may have a dynamically sized type
+
+error: aborting due to 5 previous errors
+
+Some errors have detailed explanations: E0277, E0425.
+For more information about an error, try `rustc --explain E0277`.

Diff for: tests/ui/traits/bound/on-structs-and-enums-static.rs

@@ -8,6 +8,7 @@ struct Foo<T:Trait> {
 
 static X: Foo<usize> = Foo {
 //~^ ERROR E0277
+//~| ERROR E0277
     x: 1, //~ ERROR: E0277
 };
 

Diff for: tests/ui/traits/bound/on-structs-and-enums-static.stderr

@@ -16,7 +16,25 @@ LL | struct Foo<T:Trait> {
    |              ^^^^^ required by this bound in `Foo`
 
 error[E0277]: the trait bound `usize: Trait` is not satisfied
-  --> $DIR/on-structs-and-enums-static.rs:11:8
+  --> $DIR/on-structs-and-enums-static.rs:9:11
+   |
+LL | static X: Foo<usize> = Foo {
+   |           ^^^^^^^^^^ the trait `Trait` is not implemented for `usize`
+   |
+help: this trait has no implementations, consider adding one
+  --> $DIR/on-structs-and-enums-static.rs:1:1
+   |
+LL | trait Trait {
+   | ^^^^^^^^^^^
+note: required by a bound in `Foo`
+  --> $DIR/on-structs-and-enums-static.rs:5:14
+   |
+LL | struct Foo<T:Trait> {
+   |              ^^^^^ required by this bound in `Foo`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error[E0277]: the trait bound `usize: Trait` is not satisfied
+  --> $DIR/on-structs-and-enums-static.rs:12:8
    |
 LL |     x: 1,
    |        ^ the trait `Trait` is not implemented for `usize`
@@ -32,6 +50,6 @@ note: required by a bound in `Foo`
 LL | struct Foo<T:Trait> {
    |              ^^^^^ required by this bound in `Foo`
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

Diff for: tests/ui/wf/wf-const-type.rs

@@ -10,6 +10,7 @@ struct NotCopy;
 const FOO: IsCopy<Option<NotCopy>> = IsCopy { t: None };
 //~^ ERROR E0277
 //~| ERROR E0277
+//~| ERROR E0277
 
 
 fn main() { }

Diff for: tests/ui/wf/wf-const-type.stderr

@@ -16,6 +16,25 @@ LL + #[derive(Copy)]
 LL | struct NotCopy;
    |
 
+error[E0277]: the trait bound `NotCopy: Copy` is not satisfied
+  --> $DIR/wf-const-type.rs:10:12
+   |
+LL | const FOO: IsCopy<Option<NotCopy>> = IsCopy { t: None };
+   |            ^^^^^^^^^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `NotCopy`, which is required by `Option<NotCopy>: Copy`
+   |
+   = note: required for `Option<NotCopy>` to implement `Copy`
+note: required by a bound in `IsCopy`
+  --> $DIR/wf-const-type.rs:7:17
+   |
+LL | struct IsCopy<T:Copy> { t: T }
+   |                 ^^^^ required by this bound in `IsCopy`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: consider annotating `NotCopy` with `#[derive(Copy)]`
+   |
+LL + #[derive(Copy)]
+LL | struct NotCopy;
+   |
+
 error[E0277]: the trait bound `NotCopy: Copy` is not satisfied
   --> $DIR/wf-const-type.rs:10:50
    |
@@ -34,6 +53,6 @@ LL + #[derive(Copy)]
 LL | struct NotCopy;
    |
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0277`.

Diff for: tests/ui/wf/wf-static-type.rs

@@ -10,6 +10,7 @@ struct NotCopy;
 static FOO: IsCopy<Option<NotCopy>> = IsCopy { t: None };
 //~^ ERROR E0277
 //~| ERROR E0277
+//~| ERROR E0277
 
 
 fn main() { }

Diff for: tests/ui/wf/wf-static-type.stderr

@@ -16,6 +16,25 @@ LL + #[derive(Copy)]
 LL | struct NotCopy;
    |
 
+error[E0277]: the trait bound `NotCopy: Copy` is not satisfied
+  --> $DIR/wf-static-type.rs:10:13
+   |
+LL | static FOO: IsCopy<Option<NotCopy>> = IsCopy { t: None };
+   |             ^^^^^^^^^^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `NotCopy`, which is required by `Option<NotCopy>: Copy`
+   |
+   = note: required for `Option<NotCopy>` to implement `Copy`
+note: required by a bound in `IsCopy`
+  --> $DIR/wf-static-type.rs:7:17
+   |
+LL | struct IsCopy<T:Copy> { t: T }
+   |                 ^^^^ required by this bound in `IsCopy`
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+help: consider annotating `NotCopy` with `#[derive(Copy)]`
+   |
+LL + #[derive(Copy)]
+LL | struct NotCopy;
+   |
+
 error[E0277]: the trait bound `NotCopy: Copy` is not satisfied
   --> $DIR/wf-static-type.rs:10:51
    |
@@ -34,6 +53,6 @@ LL + #[derive(Copy)]
 LL | struct NotCopy;
    |
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0277`.