pretty: trim paths of unique symbols

If a symbol name can only be imported from one place for a type, and
as long as it was not glob-imported anywhere in the current crate, we
can trim its printed path and print only the name.

This has wide implications on error messages with types, for example,
shortening `std::vec::Vec` to just `Vec`, as long as there is no other
`Vec` importable anywhere.

This adds a new '-Z trim-diagnostic-paths=false' option to control this
feature.

On the good path, with no diagnosis printed, we should try to avoid
issuing this query, so we need to prevent trimmed_def_paths query on
several cases.

This change also relies on a previous commit that differentiates
between `Debug` and `Display` on various rustc types, where the latter
is trimmed and presented to the user and the former is not.

8 files changed, 10 insertions, 10 deletions

diff --git a/src/test/ui/pattern/usefulness/exhaustive_integer_patterns.stderr b/src/test/ui/pattern/usefulness/exhaustive_integer_patterns.stderr
index 161ac477183..de831520598 100644
--- a/src/test/ui/pattern/usefulness/exhaustive_integer_patterns.stderr
+++ b/src/test/ui/pattern/usefulness/exhaustive_integer_patterns.stderr
@@ -77,7 +77,7 @@ LL |     match (0u8, Some(())) {
    |           ^^^^^^^^^^^^^^^ patterns `(0_u8, Some(_))` and `(2_u8..=u8::MAX, Some(_))` not covered
    |
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
-   = note: the matched value is of type `(u8, std::option::Option<()>)`
+   = note: the matched value is of type `(u8, Option<()>)`
 
 error[E0004]: non-exhaustive patterns: `(126_u8..=127_u8, false)` not covered
   --> $DIR/exhaustive_integer_patterns.rs:126:11
diff --git a/src/test/ui/pattern/usefulness/issue-35609.stderr b/src/test/ui/pattern/usefulness/issue-35609.stderr
index 66f904aced1..0598c8d6f38 100644
--- a/src/test/ui/pattern/usefulness/issue-35609.stderr
+++ b/src/test/ui/pattern/usefulness/issue-35609.stderr
@@ -74,7 +74,7 @@ LL |     match Some(A) {
    |           ^^^^^^^ patterns `Some(B)`, `Some(C)`, `Some(D)` and 2 more not covered
    |
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
-   = note: the matched value is of type `std::option::Option<Enum>`
+   = note: the matched value is of type `Option<Enum>`
 
 error: aborting due to 8 previous errors
 
diff --git a/src/test/ui/pattern/usefulness/match-arm-statics-2.stderr b/src/test/ui/pattern/usefulness/match-arm-statics-2.stderr
index d541597508d..f515525123e 100644
--- a/src/test/ui/pattern/usefulness/match-arm-statics-2.stderr
+++ b/src/test/ui/pattern/usefulness/match-arm-statics-2.stderr
@@ -22,7 +22,7 @@ LL |     Some(#[stable(feature = "rust1", since = "1.0.0")] T),
    |     not covered
    |
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
-   = note: the matched value is of type `std::option::Option<std::option::Option<Direction>>`
+   = note: the matched value is of type `Option<Option<Direction>>`
 
 error[E0004]: non-exhaustive patterns: `Foo { bar: Some(North), baz: NewBool(true) }` not covered
   --> $DIR/match-arm-statics-2.rs:48:11
diff --git a/src/test/ui/pattern/usefulness/match-privately-empty.stderr b/src/test/ui/pattern/usefulness/match-privately-empty.stderr
index ca9006469e2..cd157debcd4 100644
--- a/src/test/ui/pattern/usefulness/match-privately-empty.stderr
+++ b/src/test/ui/pattern/usefulness/match-privately-empty.stderr
@@ -10,7 +10,7 @@ LL |     Some(#[stable(feature = "rust1", since = "1.0.0")] T),
    |     ---- not covered
    |
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
-   = note: the matched value is of type `std::option::Option<private::Private>`
+   = note: the matched value is of type `Option<Private>`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/pattern/usefulness/match-slice-patterns.stderr b/src/test/ui/pattern/usefulness/match-slice-patterns.stderr
index ba5312d2135..88f27be0412 100644
--- a/src/test/ui/pattern/usefulness/match-slice-patterns.stderr
+++ b/src/test/ui/pattern/usefulness/match-slice-patterns.stderr
@@ -5,7 +5,7 @@ LL |     match list {
    |           ^^^^ pattern `&[_, Some(_), .., None, _]` not covered
    |
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
-   = note: the matched value is of type `&[std::option::Option<()>]`
+   = note: the matched value is of type `&[Option<()>]`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/pattern/usefulness/non-exhaustive-match-nested.stderr b/src/test/ui/pattern/usefulness/non-exhaustive-match-nested.stderr
index c9f26db6f1f..d1cab752102 100644
--- a/src/test/ui/pattern/usefulness/non-exhaustive-match-nested.stderr
+++ b/src/test/ui/pattern/usefulness/non-exhaustive-match-nested.stderr
@@ -5,7 +5,7 @@ LL |     match (l1, l2) {
    |           ^^^^^^^^ pattern `(Some(&[]), Err(_))` not covered
    |
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
-   = note: the matched value is of type `(std::option::Option<&[T]>, std::result::Result<&[T], ()>)`
+   = note: the matched value is of type `(Option<&[T]>, std::result::Result<&[T], ()>)`
 
 error[E0004]: non-exhaustive patterns: `A(C)` not covered
   --> $DIR/non-exhaustive-match-nested.rs:15:11
diff --git a/src/test/ui/pattern/usefulness/non-exhaustive-match.stderr b/src/test/ui/pattern/usefulness/non-exhaustive-match.stderr
index 5d29feb5626..12412743b83 100644
--- a/src/test/ui/pattern/usefulness/non-exhaustive-match.stderr
+++ b/src/test/ui/pattern/usefulness/non-exhaustive-match.stderr
@@ -34,7 +34,7 @@ LL |     Some(#[stable(feature = "rust1", since = "1.0.0")] T),
    |     ---- not covered
    |
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
-   = note: the matched value is of type `std::option::Option<i32>`
+   = note: the matched value is of type `Option<i32>`
 
 error[E0004]: non-exhaustive patterns: `(_, _, i32::MIN..=3_i32)` and `(_, _, 5_i32..=i32::MAX)` not covered
   --> $DIR/non-exhaustive-match.rs:14:11
@@ -76,7 +76,7 @@ LL |     match *vec {
    |           ^^^^ pattern `[]` not covered
    |
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
-   = note: the matched value is of type `[std::option::Option<isize>]`
+   = note: the matched value is of type `[Option<isize>]`
 
 error[E0004]: non-exhaustive patterns: `[_, _, _, _, ..]` not covered
   --> $DIR/non-exhaustive-match.rs:46:11
diff --git a/src/test/ui/pattern/usefulness/refutable-pattern-errors.stderr b/src/test/ui/pattern/usefulness/refutable-pattern-errors.stderr
index 8d0409a6af9..99af71cadfc 100644
--- a/src/test/ui/pattern/usefulness/refutable-pattern-errors.stderr
+++ b/src/test/ui/pattern/usefulness/refutable-pattern-errors.stderr
@@ -4,7 +4,7 @@ error[E0005]: refutable pattern in function argument: `(_, _)` not covered
 LL | fn func((1, (Some(1), 2..=3)): (isize, (Option<isize>, isize))) { }
    |         ^^^^^^^^^^^^^^^^^^^^^ pattern `(_, _)` not covered
    |
-   = note: the matched value is of type `(isize, (std::option::Option<isize>, isize))`
+   = note: the matched value is of type `(isize, (Option<isize>, isize))`
 
 error[E0005]: refutable pattern in local binding: `(i32::MIN..=0_i32, _)` and `(2_i32..=i32::MAX, _)` not covered
   --> $DIR/refutable-pattern-errors.rs:7:9
@@ -14,7 +14,7 @@ LL |     let (1, (Some(1), 2..=3)) = (1, (None, 2));
    |
    = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
-   = note: the matched value is of type `(i32, (std::option::Option<i32>, i32))`
+   = note: the matched value is of type `(i32, (Option<i32>, i32))`
 help: you might want to use `if let` to ignore the variant that isn't matched
    |
 LL |     if let (1, (Some(1), 2..=3)) = (1, (None, 2)) { /* */ }