fix misleading type annotation diagonstics

This solves the method call part of issue
https://github.com/rust-lang/rust/issues/69455
I added a `target_span` field so as to pin down the exact location of
the error. We need a dedicated field `found_exact_method_call` to
prioritize situations like the test case `issue-69455.rs`. If we reuse
`found_method_call`, `found_local_pattern` will show up first. We can
not move `found_method_call` up, it is undesirable in various
situations.

2 files changed, 47 insertions, 0 deletions

diff --git a/src/test/ui/issues/issue-69455.rs b/src/test/ui/issues/issue-69455.rs
new file mode 100644
index 00000000000..017654554be
--- /dev/null
+++ b/src/test/ui/issues/issue-69455.rs
@@ -0,0 +1,30 @@
+// Regression test for #69455: projection predicate was not satisfied.
+// Compiler should indicate the correct location of the
+// unsatisfied projection predicate
+
+pub trait Test<Rhs = Self> {
+    type Output;
+
+    fn test(self, rhs: Rhs) -> Self::Output;
+}
+
+impl Test<u32> for u64 {
+    type Output = u64;
+
+    fn test(self, other: u32) -> u64 {
+        self + (other as u64)
+    }
+}
+
+impl Test<u64> for u64 {
+    type Output = u64;
+
+    fn test(self, other: u64) -> u64 {
+        (self + other) as u64
+    }
+}
+
+fn main() {
+    let xs: Vec<u64> = vec![1, 2, 3];
+    println!("{}", 23u64.test(xs.iter().sum())); //~ ERROR: type annotations needed [E0284]
+}
diff --git a/src/test/ui/issues/issue-69455.stderr b/src/test/ui/issues/issue-69455.stderr
new file mode 100644
index 00000000000..4caa1aca9fd
--- /dev/null
+++ b/src/test/ui/issues/issue-69455.stderr
@@ -0,0 +1,17 @@
+error[E0284]: type annotations needed
+  --> $DIR/issue-69455.rs:29:26
+   |
+LL |     type Output;
+   |     ------------ `<Self as Test<Rhs>>::Output` defined here
+...
+LL |     println!("{}", 23u64.test(xs.iter().sum()));
+   |                    ------^^^^-----------------
+   |                    |     |
+   |                    |     cannot infer type for type `u64`
+   |                    this method call resolves to `<Self as Test<Rhs>>::Output`
+   |
+   = note: cannot satisfy `<u64 as Test<_>>::Output == _`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0284`.