Auto merge of #103217 - mejrs:track, r=eholk

Track where diagnostics were created.

This implements the `-Ztrack-diagnostics` flag, which uses `#[track_caller]` to track where diagnostics are created. It is meant as a debugging tool much like `-Ztreat-err-as-bug`.

For example, the following code...

```rust
struct A;
struct B;

fn main(){
    let _: A = B;
}
```
...now emits the following error message:

```
error[E0308]: mismatched types
 --> src\main.rs:5:16
  |
5 |     let _: A = B;
  |            -   ^ expected struct `A`, found struct `B`
  |            |
  |            expected due to this
-Ztrack-diagnostics: created at compiler\rustc_infer\src\infer\error_reporting\mod.rs:2275:31
```

22 files changed, 210 insertions, 0 deletions

diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 3961802529b..893249e88cf 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -166,6 +166,7 @@ pub(crate) fn new_handler(
                     unstable_opts.teach,
                     diagnostic_width,
                     false,
+                    unstable_opts.track_diagnostics,
                 )
                 .ui_testing(unstable_opts.ui_testing),
             )
@@ -184,6 +185,7 @@ pub(crate) fn new_handler(
                     json_rendered,
                     diagnostic_width,
                     false,
+                    unstable_opts.track_diagnostics,
                 )
                 .ui_testing(unstable_opts.ui_testing),
             )
diff --git a/src/librustdoc/doctest.rs b/src/librustdoc/doctest.rs
index db70029f6ec..7cbe2f1e227 100644
--- a/src/librustdoc/doctest.rs
+++ b/src/librustdoc/doctest.rs
@@ -551,6 +551,7 @@ pub(crate) fn make_test(
                 false,
                 Some(80),
                 false,
+                false,
             )
             .supports_color();
 
@@ -564,6 +565,7 @@ pub(crate) fn make_test(
                 false,
                 None,
                 false,
+                false,
             );
 
             // FIXME(misdreavus): pass `-Z treat-err-as-bug` to the doctest parser
@@ -748,6 +750,7 @@ fn check_if_attr_is_complete(source: &str, edition: Edition) -> bool {
                 false,
                 None,
                 false,
+                false,
             );
 
             let handler = Handler::with_emitter(false, None, Box::new(emitter));
diff --git a/src/test/rustdoc-ui/track-diagnostics.rs b/src/test/rustdoc-ui/track-diagnostics.rs
new file mode 100644
index 00000000000..fcc50a7aba0
--- /dev/null
+++ b/src/test/rustdoc-ui/track-diagnostics.rs
@@ -0,0 +1,10 @@
+// compile-flags: -Z track-diagnostics
+// error-pattern: created at
+
+// Normalize the emitted location so this doesn't need
+// updating everytime someone adds or removes a line.
+// normalize-stderr-test ".rs:\d+:\d+" -> ".rs:LL:CC"
+
+struct A;
+struct B;
+const S: A = B;
diff --git a/src/test/rustdoc-ui/track-diagnostics.stderr b/src/test/rustdoc-ui/track-diagnostics.stderr
new file mode 100644
index 00000000000..ec303186253
--- /dev/null
+++ b/src/test/rustdoc-ui/track-diagnostics.stderr
@@ -0,0 +1,10 @@
+error[E0308]: mismatched types
+  --> $DIR/track-diagnostics.rs:LL:CC
+   |
+LL | const S: A = B;
+   |              ^ expected struct `A`, found struct `B`
+-Ztrack-diagnostics: created at compiler/rustc_infer/src/infer/error_reporting/mod.rs:LL:CC
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/rustdoc-ui/z-help.stdout b/src/test/rustdoc-ui/z-help.stdout
index 46f11d2e5d1..22e37821322 100644
--- a/src/test/rustdoc-ui/z-help.stdout
+++ b/src/test/rustdoc-ui/z-help.stdout
@@ -171,6 +171,7 @@
     -Z                             time-passes=val -- measure time of each rustc pass (default: no)
     -Z                               tls-model=val -- choose the TLS model to use (`rustc --print tls-models` for details)
     -Z                            trace-macros=val -- for every macro invocation, print its name and arguments (default: no)
+    -Z                       track-diagnostics=val -- tracks where in rustc a diagnostic was emitted
     -Z                translate-additional-ftl=val -- additional fluent translation to preferentially use (for testing translation)
     -Z        translate-directionality-markers=val -- emit directionality isolation markers in translated diagnostics
     -Z                          translate-lang=val -- language identifier for diagnostic output
diff --git a/src/test/ui/track-diagnostics/track.rs b/src/test/ui/track-diagnostics/track.rs
new file mode 100644
index 00000000000..61b9137eadd
--- /dev/null
+++ b/src/test/ui/track-diagnostics/track.rs
@@ -0,0 +1,11 @@
+// compile-flags: -Z track-diagnostics
+// error-pattern: created at
+
+// Normalize the emitted location so this doesn't need
+// updating everytime someone adds or removes a line.
+// normalize-stderr-test ".rs:\d+:\d+" -> ".rs:LL:CC"
+// normalize-stderr-test "note: rustc .+ running on .+" -> "note: rustc $$VERSION running on $$TARGET"
+
+fn main() {
+    break rust
+}
diff --git a/src/test/ui/track-diagnostics/track.stderr b/src/test/ui/track-diagnostics/track.stderr
new file mode 100644
index 00000000000..ba26cf7c745
--- /dev/null
+++ b/src/test/ui/track-diagnostics/track.stderr
@@ -0,0 +1,26 @@
+error[E0425]: cannot find value `rust` in this scope
+  --> $DIR/track.rs:LL:CC
+   |
+LL |     break rust
+   |           ^^^^ not found in this scope
+-Ztrack-diagnostics: created at compiler/rustc_resolve/src/late/diagnostics.rs:LL:CC
+
+error[E0268]: `break` outside of a loop
+  --> $DIR/track.rs:LL:CC
+   |
+LL |     break rust
+   |     ^^^^^^^^^^ cannot `break` outside of a loop
+-Ztrack-diagnostics: created at compiler/rustc_passes/src/loops.rs:LL:CC
+
+error: internal compiler error: It looks like you're trying to break rust; would you like some ICE?
+
+note: the compiler expectedly panicked. this is a feature.
+
+note: we would appreciate a joke overview: https://github.com/rust-lang/rust/issues/43162#issuecomment-320764675
+
+note: rustc $VERSION running on $TARGET
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0268, E0425.
+For more information about an error, try `rustc --explain E0268`.
diff --git a/src/test/ui/track-diagnostics/track2.rs b/src/test/ui/track-diagnostics/track2.rs
new file mode 100644
index 00000000000..dc105c61d72
--- /dev/null
+++ b/src/test/ui/track-diagnostics/track2.rs
@@ -0,0 +1,10 @@
+// compile-flags: -Z track-diagnostics
+// error-pattern: created at
+
+// Normalize the emitted location so this doesn't need
+// updating everytime someone adds or removes a line.
+// normalize-stderr-test ".rs:\d+:\d+" -> ".rs:LL:CC"
+
+fn main() {
+    let _moved @ _from = String::from("foo");
+}
diff --git a/src/test/ui/track-diagnostics/track2.stderr b/src/test/ui/track-diagnostics/track2.stderr
new file mode 100644
index 00000000000..38a621da816
--- /dev/null
+++ b/src/test/ui/track-diagnostics/track2.stderr
@@ -0,0 +1,13 @@
+error[E0382]: use of moved value
+  --> $DIR/track2.rs:LL:CC
+   |
+LL |     let _moved @ _from = String::from("foo");
+   |         ^^^^^^   -----   ------------------- move occurs because value has type `String`, which does not implement the `Copy` trait
+   |         |        |
+   |         |        value moved here
+   |         value used here after move
+-Ztrack-diagnostics: created at compiler/rustc_borrowck/src/borrowck_errors.rs:LL:CC
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0382`.
diff --git a/src/test/ui/track-diagnostics/track3.rs b/src/test/ui/track-diagnostics/track3.rs
new file mode 100644
index 00000000000..0699239503a
--- /dev/null
+++ b/src/test/ui/track-diagnostics/track3.rs
@@ -0,0 +1,10 @@
+// compile-flags: -Z track-diagnostics
+// error-pattern: created at
+
+// Normalize the emitted location so this doesn't need
+// updating everytime someone adds or removes a line.
+// normalize-stderr-test ".rs:\d+:\d+" -> ".rs:LL:CC"
+
+fn main() {
+    let _unimported = Blah { field: u8 };
+}
diff --git a/src/test/ui/track-diagnostics/track3.stderr b/src/test/ui/track-diagnostics/track3.stderr
new file mode 100644
index 00000000000..dc468d7e8ee
--- /dev/null
+++ b/src/test/ui/track-diagnostics/track3.stderr
@@ -0,0 +1,18 @@
+error[E0422]: cannot find struct, variant or union type `Blah` in this scope
+  --> $DIR/track3.rs:LL:CC
+   |
+LL |     let _unimported = Blah { field: u8 };
+   |                       ^^^^ not found in this scope
+-Ztrack-diagnostics: created at compiler/rustc_resolve/src/late/diagnostics.rs:LL:CC
+
+error[E0423]: expected value, found builtin type `u8`
+  --> $DIR/track3.rs:LL:CC
+   |
+LL |     let _unimported = Blah { field: u8 };
+   |                                     ^^ not a value
+-Ztrack-diagnostics: created at compiler/rustc_resolve/src/late/diagnostics.rs:LL:CC
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0422, E0423.
+For more information about an error, try `rustc --explain E0422`.
diff --git a/src/test/ui/track-diagnostics/track4.rs b/src/test/ui/track-diagnostics/track4.rs
new file mode 100644
index 00000000000..35eec799bba
--- /dev/null
+++ b/src/test/ui/track-diagnostics/track4.rs
@@ -0,0 +1,13 @@
+// compile-flags: -Z track-diagnostics
+// error-pattern: created at
+
+// Normalize the emitted location so this doesn't need
+// updating everytime someone adds or removes a line.
+// normalize-stderr-test ".rs:\d+:\d+" -> ".rs:LL:CC"
+
+pub onion {
+    Owo(u8),
+    Uwu(i8),
+}
+
+fn main() {}
diff --git a/src/test/ui/track-diagnostics/track4.stderr b/src/test/ui/track-diagnostics/track4.stderr
new file mode 100644
index 00000000000..c4668444c4b
--- /dev/null
+++ b/src/test/ui/track-diagnostics/track4.stderr
@@ -0,0 +1,14 @@
+error: missing `struct` for struct definition
+  --> $DIR/track4.rs:LL:CC
+   |
+LL | pub onion {
+   |    ^
+-Ztrack-diagnostics: created at compiler/rustc_parse/src/parser/diagnostics.rs:LL:CC
+   |
+help: add `struct` here to parse `onion` as a public struct
+   |
+LL | pub struct onion {
+   |     ++++++
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/track-diagnostics/track5.rs b/src/test/ui/track-diagnostics/track5.rs
new file mode 100644
index 00000000000..c41d9424e85
--- /dev/null
+++ b/src/test/ui/track-diagnostics/track5.rs
@@ -0,0 +1,8 @@
+// compile-flags: -Z track-diagnostics
+// error-pattern: created at
+
+// Normalize the emitted location so this doesn't need
+// updating everytime someone adds or removes a line.
+// normalize-stderr-test ".rs:\d+:\d+" -> ".rs:LL:CC"
+
+}
diff --git a/src/test/ui/track-diagnostics/track5.stderr b/src/test/ui/track-diagnostics/track5.stderr
new file mode 100644
index 00000000000..aa54f92b6c0
--- /dev/null
+++ b/src/test/ui/track-diagnostics/track5.stderr
@@ -0,0 +1,9 @@
+error: unexpected closing delimiter: `}`
+  --> $DIR/track5.rs:LL:CC
+   |
+LL | }
+   | ^ unexpected closing delimiter
+-Ztrack-diagnostics: created at compiler/rustc_parse/src/lexer/tokentrees.rs:LL:CC
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/track-diagnostics/track6.rs b/src/test/ui/track-diagnostics/track6.rs
new file mode 100644
index 00000000000..307e3101849
--- /dev/null
+++ b/src/test/ui/track-diagnostics/track6.rs
@@ -0,0 +1,14 @@
+// compile-flags: -Z track-diagnostics
+// error-pattern: created at
+
+
+
+pub trait Foo {
+    fn bar();
+}
+
+impl <T> Foo for T {
+    default fn bar() {}
+}
+
+fn main() {}
diff --git a/src/test/ui/track-diagnostics/track6.stderr b/src/test/ui/track-diagnostics/track6.stderr
new file mode 100644
index 00000000000..1c7537633ff
--- /dev/null
+++ b/src/test/ui/track-diagnostics/track6.stderr
@@ -0,0 +1,13 @@
+error[E0658]: specialization is unstable
+  --> $DIR/track6.rs:11:5
+   |
+LL |     default fn bar() {}
+   |     ^^^^^^^^^^^^^^^^^^^
+-Ztrack-diagnostics: created at $COMPILER_DIR/rustc_session/src/parse.rs:93:5
+   |
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+   = help: add `#![feature(specialization)]` to the crate attributes to enable
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0658`.
diff --git a/src/tools/clippy/clippy_lints/src/doc.rs b/src/tools/clippy/clippy_lints/src/doc.rs
index 24d6a6951af..daaab79fef9 100644
--- a/src/tools/clippy/clippy_lints/src/doc.rs
+++ b/src/tools/clippy/clippy_lints/src/doc.rs
@@ -691,6 +691,7 @@ fn check_code(cx: &LateContext<'_>, text: &str, edition: Edition, span: Span) {
                     false,
                     None,
                     false,
+                    false,
                 );
                 let handler = Handler::with_emitter(false, None, Box::new(emitter));
                 let sess = ParseSess::with_span_handler(handler, sm);
diff --git a/src/tools/clippy/src/driver.rs b/src/tools/clippy/src/driver.rs
index b12208ac62a..ae54b2078a6 100644
--- a/src/tools/clippy/src/driver.rs
+++ b/src/tools/clippy/src/driver.rs
@@ -179,6 +179,7 @@ fn report_clippy_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str) {
         false,
         None,
         false,
+        false,
     ));
     let handler = rustc_errors::Handler::with_emitter(true, None, emitter);
 
diff --git a/src/tools/clippy/tests/ui/track-diagnostics.rs b/src/tools/clippy/tests/ui/track-diagnostics.rs
new file mode 100644
index 00000000000..fa9221ed02d
--- /dev/null
+++ b/src/tools/clippy/tests/ui/track-diagnostics.rs
@@ -0,0 +1,12 @@
+// compile-flags: -Z track-diagnostics
+// error-pattern: created at
+
+// Normalize the emitted location so this doesn't need
+// updating everytime someone adds or removes a line.
+// normalize-stderr-test ".rs:\d+:\d+" -> ".rs:LL:CC"
+
+struct A;
+struct B;
+const S: A = B;
+
+fn main() {}
diff --git a/src/tools/clippy/tests/ui/track-diagnostics.stderr b/src/tools/clippy/tests/ui/track-diagnostics.stderr
new file mode 100644
index 00000000000..ec303186253
--- /dev/null
+++ b/src/tools/clippy/tests/ui/track-diagnostics.stderr
@@ -0,0 +1,10 @@
+error[E0308]: mismatched types
+  --> $DIR/track-diagnostics.rs:LL:CC
+   |
+LL | const S: A = B;
+   |              ^ expected struct `A`, found struct `B`
+-Ztrack-diagnostics: created at compiler/rustc_infer/src/infer/error_reporting/mod.rs:LL:CC
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/tools/rustfmt/src/parse/session.rs b/src/tools/rustfmt/src/parse/session.rs
index 6efeee98fea..6bfec79cd70 100644
--- a/src/tools/rustfmt/src/parse/session.rs
+++ b/src/tools/rustfmt/src/parse/session.rs
@@ -134,6 +134,7 @@ fn default_handler(
             false,
             None,
             false,
+            false,
         ))
     };
     Handler::with_emitter(