Rework collapse method to work correctly with more complex supertrait graphs

8 files changed, 219 insertions, 0 deletions

diff --git a/tests/ui/methods/supertrait-shadowing/common-ancestor-2.rs b/tests/ui/methods/supertrait-shadowing/common-ancestor-2.rs
new file mode 100644
index 00000000000..91a64561824
--- /dev/null
+++ b/tests/ui/methods/supertrait-shadowing/common-ancestor-2.rs
@@ -0,0 +1,32 @@
+//@ run-pass
+//@ check-run-results
+
+#![feature(supertrait_item_shadowing)]
+#![warn(supertrait_item_shadowing_usage)]
+#![allow(dead_code)]
+
+trait A {
+    fn hello(&self) {
+        println!("A");
+    }
+}
+impl<T> A for T {}
+
+trait B {
+    fn hello(&self) {
+        println!("B");
+    }
+}
+impl<T> B for T {}
+
+trait C: A + B {
+    fn hello(&self) {
+        println!("C");
+    }
+}
+impl<T> C for T {}
+
+fn main() {
+    ().hello();
+    //~^ WARN trait item `hello` from `C` shadows identically named item from supertrait
+}
diff --git a/tests/ui/methods/supertrait-shadowing/common-ancestor-2.run.stdout b/tests/ui/methods/supertrait-shadowing/common-ancestor-2.run.stdout
new file mode 100644
index 00000000000..3cc58df8375
--- /dev/null
+++ b/tests/ui/methods/supertrait-shadowing/common-ancestor-2.run.stdout
@@ -0,0 +1 @@
+C
diff --git a/tests/ui/methods/supertrait-shadowing/common-ancestor-2.stderr b/tests/ui/methods/supertrait-shadowing/common-ancestor-2.stderr
new file mode 100644
index 00000000000..a22c5430fef
--- /dev/null
+++ b/tests/ui/methods/supertrait-shadowing/common-ancestor-2.stderr
@@ -0,0 +1,27 @@
+warning: trait item `hello` from `C` shadows identically named item from supertrait
+  --> $DIR/common-ancestor-2.rs:30:8
+   |
+LL |     ().hello();
+   |        ^^^^^
+   |
+note: item from `C` shadows a supertrait item
+  --> $DIR/common-ancestor-2.rs:23:5
+   |
+LL |     fn hello(&self) {
+   |     ^^^^^^^^^^^^^^^
+note: items from several supertraits are shadowed: `A` and `B`
+  --> $DIR/common-ancestor-2.rs:9:5
+   |
+LL |     fn hello(&self) {
+   |     ^^^^^^^^^^^^^^^
+...
+LL |     fn hello(&self) {
+   |     ^^^^^^^^^^^^^^^
+note: the lint level is defined here
+  --> $DIR/common-ancestor-2.rs:5:9
+   |
+LL | #![warn(supertrait_item_shadowing_usage)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: 1 warning emitted
+
diff --git a/tests/ui/methods/supertrait-shadowing/common-ancestor-3.rs b/tests/ui/methods/supertrait-shadowing/common-ancestor-3.rs
new file mode 100644
index 00000000000..c2b0ef39bb1
--- /dev/null
+++ b/tests/ui/methods/supertrait-shadowing/common-ancestor-3.rs
@@ -0,0 +1,41 @@
+//@ run-pass
+//@ check-run-results
+
+#![feature(supertrait_item_shadowing)]
+#![warn(supertrait_item_shadowing_usage)]
+#![allow(dead_code)]
+
+trait A {
+    fn hello(&self) {
+        println!("A");
+    }
+}
+impl<T> A for T {}
+
+trait B {
+    fn hello(&self) {
+        println!("B");
+    }
+}
+impl<T> B for T {}
+
+trait C: A + B {
+    fn hello(&self) {
+        println!("C");
+    }
+}
+impl<T> C for T {}
+
+// `D` extends `C` which extends `B` and `A`
+
+trait D: C {
+    fn hello(&self) {
+        println!("D");
+    }
+}
+impl<T> D for T {}
+
+fn main() {
+    ().hello();
+    //~^ WARN trait item `hello` from `D` shadows identically named item from supertrait
+}
diff --git a/tests/ui/methods/supertrait-shadowing/common-ancestor-3.run.stdout b/tests/ui/methods/supertrait-shadowing/common-ancestor-3.run.stdout
new file mode 100644
index 00000000000..17848105018
--- /dev/null
+++ b/tests/ui/methods/supertrait-shadowing/common-ancestor-3.run.stdout
@@ -0,0 +1 @@
+D
diff --git a/tests/ui/methods/supertrait-shadowing/common-ancestor-3.stderr b/tests/ui/methods/supertrait-shadowing/common-ancestor-3.stderr
new file mode 100644
index 00000000000..072f4fe0208
--- /dev/null
+++ b/tests/ui/methods/supertrait-shadowing/common-ancestor-3.stderr
@@ -0,0 +1,30 @@
+warning: trait item `hello` from `D` shadows identically named item from supertrait
+  --> $DIR/common-ancestor-3.rs:39:8
+   |
+LL |     ().hello();
+   |        ^^^^^
+   |
+note: item from `D` shadows a supertrait item
+  --> $DIR/common-ancestor-3.rs:32:5
+   |
+LL |     fn hello(&self) {
+   |     ^^^^^^^^^^^^^^^
+note: items from several supertraits are shadowed: `A`, `B`, and `C`
+  --> $DIR/common-ancestor-3.rs:9:5
+   |
+LL |     fn hello(&self) {
+   |     ^^^^^^^^^^^^^^^
+...
+LL |     fn hello(&self) {
+   |     ^^^^^^^^^^^^^^^
+...
+LL |     fn hello(&self) {
+   |     ^^^^^^^^^^^^^^^
+note: the lint level is defined here
+  --> $DIR/common-ancestor-3.rs:5:9
+   |
+LL | #![warn(supertrait_item_shadowing_usage)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+warning: 1 warning emitted
+
diff --git a/tests/ui/methods/supertrait-shadowing/no-common-ancestor-2.rs b/tests/ui/methods/supertrait-shadowing/no-common-ancestor-2.rs
new file mode 100644
index 00000000000..2834ca31b71
--- /dev/null
+++ b/tests/ui/methods/supertrait-shadowing/no-common-ancestor-2.rs
@@ -0,0 +1,37 @@
+#![feature(supertrait_item_shadowing)]
+
+trait A {
+    fn hello(&self) {
+        println!("A");
+    }
+}
+impl<T> A for T {}
+
+trait B {
+    fn hello(&self) {
+        println!("B");
+    }
+}
+impl<T> B for T {}
+
+trait C: A + B {
+    fn hello(&self) {
+        println!("C");
+    }
+}
+impl<T> C for T {}
+
+// Since `D` is not a subtrait of `C`,
+// we have no obvious lower bound.
+
+trait D: B {
+    fn hello(&self) {
+        println!("D");
+    }
+}
+impl<T> D for T {}
+
+fn main() {
+    ().hello();
+    //~^ ERROR multiple applicable items in scope
+}
diff --git a/tests/ui/methods/supertrait-shadowing/no-common-ancestor-2.stderr b/tests/ui/methods/supertrait-shadowing/no-common-ancestor-2.stderr
new file mode 100644
index 00000000000..231cb9b1cb2
--- /dev/null
+++ b/tests/ui/methods/supertrait-shadowing/no-common-ancestor-2.stderr
@@ -0,0 +1,50 @@
+error[E0034]: multiple applicable items in scope
+  --> $DIR/no-common-ancestor-2.rs:35:8
+   |
+LL |     ().hello();
+   |        ^^^^^ multiple `hello` found
+   |
+note: candidate #1 is defined in an impl of the trait `A` for the type `T`
+  --> $DIR/no-common-ancestor-2.rs:4:5
+   |
+LL |     fn hello(&self) {
+   |     ^^^^^^^^^^^^^^^
+note: candidate #2 is defined in an impl of the trait `B` for the type `T`
+  --> $DIR/no-common-ancestor-2.rs:11:5
+   |
+LL |     fn hello(&self) {
+   |     ^^^^^^^^^^^^^^^
+note: candidate #3 is defined in an impl of the trait `C` for the type `T`
+  --> $DIR/no-common-ancestor-2.rs:18:5
+   |
+LL |     fn hello(&self) {
+   |     ^^^^^^^^^^^^^^^
+note: candidate #4 is defined in an impl of the trait `D` for the type `T`
+  --> $DIR/no-common-ancestor-2.rs:28:5
+   |
+LL |     fn hello(&self) {
+   |     ^^^^^^^^^^^^^^^
+help: disambiguate the method for candidate #1
+   |
+LL -     ().hello();
+LL +     A::hello(&());
+   |
+help: disambiguate the method for candidate #2
+   |
+LL -     ().hello();
+LL +     B::hello(&());
+   |
+help: disambiguate the method for candidate #3
+   |
+LL -     ().hello();
+LL +     C::hello(&());
+   |
+help: disambiguate the method for candidate #4
+   |
+LL -     ().hello();
+LL +     D::hello(&());
+   |
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0034`.