Rollup merge of rust-lang#105188 - compiler-errors:verbose-ty-err, r=TaKO8Ki

Don't elide type information when printing E0308 with `-Zverbose`

When we pass `-Zverbose`, we kinda expect for all `_` to be replaced with more descriptive information, for example --

```
   = note: expected fn pointer `fn(_, u32)`
                 found fn item `fn(_, i32) {foo}`
```

Where `_` is the "identical" part of the fn signatures, now gets rendered as:

```
   = note: expected fn pointer `fn(i32, u32)`
                 found fn item `fn(i32, i32) {foo}`
```

Author: Yuki Okushi

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -1255,7 +1255,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     let num_display_types = consts_offset - regions_len;
                     for (i, (ta1, ta2)) in type_arguments.take(num_display_types).enumerate() {
                         let i = i + regions_len;
-                        if ta1 == ta2 {
+                        if ta1 == ta2 && !self.tcx.sess.verbose() {
                             values.0.push_normal("_");
                             values.1.push_normal("_");
                         } else {
@@ -1271,7 +1271,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     let const_arguments = sub1.consts().zip(sub2.consts());
                     for (i, (ca1, ca2)) in const_arguments.enumerate() {
                         let i = i + consts_offset;
-                        if ca1 == ca2 {
+                        if ca1 == ca2 && !self.tcx.sess.verbose() {
                             values.0.push_normal("_");
                             values.1.push_normal("_");
                         } else {
@@ -1450,7 +1450,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             (ty::FnPtr(sig1), ty::FnPtr(sig2)) => self.cmp_fn_sig(sig1, sig2),
 
             _ => {
-                if t1 == t2 {
+                if t1 == t2 && !self.tcx.sess.verbose() {
                     // The two types are the same, elide and don't highlight.
                     (DiagnosticStyledString::normal("_"), DiagnosticStyledString::normal("_"))
                 } else {

src/test/ui/fn/signature-error-reporting-under-verbose.rs

@@ -0,0 +1,15 @@
+// compile-flags: -Zverbose
+
+fn foo(_: i32, _: i32) {}
+
+fn needs_ptr(_: fn(i32, u32)) {}
+//~^ NOTE function defined here
+//~| NOTE
+
+fn main() {
+    needs_ptr(foo);
+    //~^ ERROR mismatched types
+    //~| NOTE expected `u32`, found `i32`
+    //~| NOTE expected fn pointer `fn(i32, u32)`
+    //~| NOTE arguments to this function are incorrect
+}

src/test/ui/fn/signature-error-reporting-under-verbose.stderr

@@ -0,0 +1,19 @@
+error[E0308]: mismatched types
+  --> $DIR/signature-error-reporting-under-verbose.rs:10:15
+   |
+LL |     needs_ptr(foo);
+   |     --------- ^^^ expected `u32`, found `i32`
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note: expected fn pointer `fn(i32, u32)`
+                 found fn item `fn(i32, i32) {foo}`
+note: function defined here
+  --> $DIR/signature-error-reporting-under-verbose.rs:5:4
+   |
+LL | fn needs_ptr(_: fn(i32, u32)) {}
+   |    ^^^^^^^^^ ---------------
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.