Stop bailing out from compilation just because there were incoherent traits

Author: oli-obk

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -1990,6 +1990,10 @@ pub(super) fn check_type_bounds<'tcx>(
     impl_ty: ty::AssocItem,
     impl_trait_ref: ty::TraitRef<'tcx>,
 ) -> Result<(), ErrorGuaranteed> {
+    // Avoid bogus "type annotations needed `Foo: Bar`" errors on `impl Bar for Foo` in case
+    // other `Foo` impls are incoherent.
+    tcx.ensure().coherent_trait(impl_trait_ref.def_id)?;
+
     let param_env = tcx.param_env(impl_ty.def_id);
     debug!(?param_env);
 

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1006,6 +1006,10 @@ fn check_associated_item(
     enter_wf_checking_ctxt(tcx, span, item_id, |wfcx| {
         let item = tcx.associated_item(item_id);
 
+        // Avoid bogus "type annotations needed `Foo: Bar`" errors on `impl Bar for Foo` in case
+        // other `Foo` impls are incoherent.
+        tcx.ensure().coherent_trait(tcx.local_parent(item_id))?;
+
         let self_ty = match item.container {
             ty::TraitContainer => tcx.types.self_param,
             ty::ImplContainer => tcx.type_of(item.container_id(tcx)).instantiate_identity(),
@@ -1292,6 +1296,9 @@ fn check_impl<'tcx>(
                 // therefore don't need to be WF (the trait's `Self: Trait` predicate
                 // won't hold).
                 let trait_ref = tcx.impl_trait_ref(item.owner_id).unwrap().instantiate_identity();
+                // Avoid bogus "type annotations needed `Foo: Bar`" errors on `impl Bar for Foo` in case
+                // other `Foo` impls are incoherent.
+                tcx.ensure().coherent_trait(trait_ref.def_id)?;
                 let trait_ref = wfcx.normalize(
                     ast_trait_ref.path.span,
                     Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)),

compiler/rustc_hir_analysis/src/lib.rs

@@ -169,11 +169,11 @@ pub fn check_crate(tcx: TyCtxt<'_>) -> Result<(), ErrorGuaranteed> {
 
     tcx.sess.time("coherence_checking", || {
         // Check impls constrain their parameters
-        let mut res =
+        let res =
             tcx.hir().try_par_for_each_module(|module| tcx.ensure().check_mod_impl_wf(module));
 
         for &trait_def_id in tcx.all_local_trait_impls(()).keys() {
-            res = res.and(tcx.ensure().coherent_trait(trait_def_id));
+            let _ = tcx.ensure().coherent_trait(trait_def_id);
         }
         // these queries are executed for side-effects (error reporting):
         res.and(tcx.ensure().crate_inherent_impls(()))

tests/ui/associated-consts/issue-105330.rs

@@ -14,5 +14,6 @@ fn foo<A: TraitWAssocConst<A=32>>() { //~ ERROR E0658
 
 fn main<A: TraitWAssocConst<A=32>>() {
     //~^ ERROR E0658
+    //~| ERROR E0131
     foo::<Demo>();
 }

tests/ui/associated-consts/issue-105330.stderr

@@ -43,7 +43,13 @@ LL | impl TraitWAssocConst for impl Demo {
    |
    = note: `impl Trait` is only allowed in arguments and return types of functions and methods
 
-error: aborting due to 5 previous errors
+error[E0131]: `main` function is not allowed to have generic parameters
+  --> $DIR/issue-105330.rs:15:8
+   |
+LL | fn main<A: TraitWAssocConst<A=32>>() {
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^ `main` cannot have generic parameters
+
+error: aborting due to 6 previous errors
 
-Some errors have detailed explanations: E0404, E0562, E0658.
-For more information about an error, try `rustc --explain E0404`.
+Some errors have detailed explanations: E0131, E0404, E0562, E0658.
+For more information about an error, try `rustc --explain E0131`.

tests/ui/coherence/associated-type2.rs

@@ -0,0 +1,20 @@
+//! A regression test for #120343. The overlap error was previously
+//! silenced in coherence because projecting `<() as ToUnit>::Unit`
+//! failed. Then then silenced the missing items error in the `ToUnit`
+//! impl, causing us to not emit any errors and ICEing due to a
+//! `span_delay_bug`.
+
+trait ToUnit {
+    type Unit;
+}
+
+impl<T> ToUnit for *const T {}
+//~^ ERROR: not all trait items implemented
+
+trait Overlap<T> {}
+
+impl<T> Overlap<T> for T {}
+
+impl<T> Overlap<<*const T as ToUnit>::Unit> for T {}
+
+fn main() {}

tests/ui/coherence/associated-type2.stderr

@@ -0,0 +1,12 @@
+error[E0046]: not all trait items implemented, missing: `Unit`
+  --> $DIR/associated-type2.rs:11:1
+   |
+LL |     type Unit;
+   |     --------- `Unit` from trait
+...
+LL | impl<T> ToUnit for *const T {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `Unit` in implementation
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0046`.

tests/ui/coherence/coherence-blanket-conflicts-with-specific-multidispatch.rs

@@ -22,6 +22,7 @@ struct MyType {
 impl MyTrait<MyType> for MyType {
 //~^ ERROR E0119
     fn get(&self) -> usize { (*self).clone() }
+    //~^ ERROR incompatible type
 }
 
 fn main() { }

tests/ui/coherence/coherence-blanket-conflicts-with-specific-multidispatch.stderr

@@ -7,6 +7,24 @@ LL | impl<T> MyTrait<T> for T {
 LL | impl MyTrait<MyType> for MyType {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `MyType`
 
-error: aborting due to 1 previous error
+error[E0053]: method `get` has an incompatible type for trait
+  --> $DIR/coherence-blanket-conflicts-with-specific-multidispatch.rs:24:22
+   |
+LL |     fn get(&self) -> usize { (*self).clone() }
+   |                      ^^^^^
+   |                      |
+   |                      expected `MyType`, found `usize`
+   |                      help: change the output type to match the trait: `MyType`
+   |
+note: type in trait
+  --> $DIR/coherence-blanket-conflicts-with-specific-multidispatch.rs:8:22
+   |
+LL |     fn get(&self) -> T;
+   |                      ^
+   = note: expected signature `fn(&MyType) -> MyType`
+              found signature `fn(&MyType) -> usize`
+
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0119`.
+Some errors have detailed explanations: E0053, E0119.
+For more information about an error, try `rustc --explain E0053`.

tests/ui/coherence/coherence-orphan.rs

@@ -9,10 +9,13 @@ struct TheType;
 
 impl TheTrait<usize> for isize { }
 //~^ ERROR E0117
+//~| ERROR not all trait items implemented
 
 impl TheTrait<TheType> for isize { }
+//~^ ERROR not all trait items implemented
 
 impl TheTrait<isize> for TheType { }
+//~^ ERROR not all trait items implemented
 
 impl !Send for Vec<isize> { } //~ ERROR E0117
 //~^ WARNING