Rollup merge of rust-lang#126588 - linyihai:trim-extra-comma, r=petrochenkov

Added more scenarios where comma to be removed in the function arg

This is an attempt to address the problem methion in rust-lang#106304 (comment).

Copy the annotation to explain the fix

If the next Error::Extra ("next") doesn't next to current ("current")

```
fn foo(_: (), _: u32) {}
- foo("current", (), 1u32, "next")
+ foo((), 1u32)
```

If the previous error is not a `Error::Extra`, then do not trim the next comma

```
- foo((), "current", 42u32, "next")
+ foo((), 42u32)
```

Frankly, this is a fix from a test case and may not cover all scenarios

Author: matthiaskrgr

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -1097,6 +1097,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let mut only_extras_so_far = errors
             .peek()
             .is_some_and(|first| matches!(first, Error::Extra(arg_idx) if arg_idx.index() == 0));
+        let mut prev_extra_idx = None;
         let mut suggestions = vec![];
         while let Some(error) = errors.next() {
             only_extras_so_far &= matches!(error, Error::Extra(_));
@@ -1165,11 +1166,29 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         //     fn f() {}
                         //   - f(0, 1,)
                         //   + f()
-                        if only_extras_so_far
-                            && !errors
-                                .peek()
-                                .is_some_and(|next_error| matches!(next_error, Error::Extra(_)))
-                        {
+                        let trim_next_comma = match errors.peek() {
+                            Some(Error::Extra(provided_idx))
+                                if only_extras_so_far
+                                    && provided_idx.index() > arg_idx.index() + 1 =>
+                            // If the next Error::Extra ("next") doesn't next to current ("current"),
+                            // fn foo(_: (), _: u32) {}
+                            // - foo("current", (), 1u32, "next")
+                            // + foo((), 1u32)
+                            // If the previous error is not a `Error::Extra`, then do not trim the next comma
+                            // - foo((), "current", 42u32, "next")
+                            // + foo((), 42u32)
+                            {
+                                prev_extra_idx.map_or(true, |prev_extra_idx| {
+                                    prev_extra_idx + 1 == arg_idx.index()
+                                })
+                            }
+                            // If no error left, we need to delete the next comma
+                            None if only_extras_so_far => true,
+                            // Not sure if other error type need to be handled as well
+                            _ => false,
+                        };
+
+                        if trim_next_comma {
                             let next = provided_arg_tys
                                 .get(arg_idx + 1)
                                 .map(|&(_, sp)| sp)
@@ -1192,6 +1211,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             SuggestionText::Remove(_) => SuggestionText::Remove(true),
                             _ => SuggestionText::DidYouMean,
                         };
+                        prev_extra_idx = Some(arg_idx.index())
                     }
                 }
                 Error::Missing(expected_idx) => {

tests/ui/argument-suggestions/issue-109425.fixed

@@ -15,6 +15,10 @@ fn main() {
     //~^ error: this function takes 1 argument but 3 arguments were supplied
     is(0, ""); // is(0, "")
     //~^ error: this function takes 2 arguments but 4 arguments were supplied
+    is(1, "");
+    //~^ error: this function takes 2 arguments but 4 arguments were supplied
+    is(1, "");
+    //~^ error: this function takes 2 arguments but 4 arguments were supplied
     s("");     // s("")
     //~^ error: this function takes 1 argument but 3 arguments were supplied
 }

tests/ui/argument-suggestions/issue-109425.rs

@@ -15,6 +15,10 @@ fn main() {
     //~^ error: this function takes 1 argument but 3 arguments were supplied
     is(0, 1, 2, ""); // is(0, "")
     //~^ error: this function takes 2 arguments but 4 arguments were supplied
+    is((), 1, "", ());
+    //~^ error: this function takes 2 arguments but 4 arguments were supplied
+    is(1, (), "", ());
+    //~^ error: this function takes 2 arguments but 4 arguments were supplied
     s(0, 1, "");     // s("")
     //~^ error: this function takes 1 argument but 3 arguments were supplied
 }

tests/ui/argument-suggestions/issue-109425.stderr

@@ -74,9 +74,47 @@ LL -     is(0, 1, 2, ""); // is(0, "")
 LL +     is(0, ""); // is(0, "")
    |
 
-error[E0061]: this function takes 1 argument but 3 arguments were supplied
+error[E0061]: this function takes 2 arguments but 4 arguments were supplied
   --> $DIR/issue-109425.rs:18:5
    |
+LL |     is((), 1, "", ());
+   |     ^^ --         -- unexpected argument #4 of type `()`
+   |        |
+   |        unexpected argument #1 of type `()`
+   |
+note: function defined here
+  --> $DIR/issue-109425.rs:5:4
+   |
+LL | fn is(_: u32, _: &str) {}
+   |    ^^ ------  -------
+help: remove the extra arguments
+   |
+LL -     is((), 1, "", ());
+LL +     is(1, "");
+   |
+
+error[E0061]: this function takes 2 arguments but 4 arguments were supplied
+  --> $DIR/issue-109425.rs:20:5
+   |
+LL |     is(1, (), "", ());
+   |     ^^    --      -- unexpected argument #4 of type `()`
+   |           |
+   |           unexpected argument #2 of type `()`
+   |
+note: function defined here
+  --> $DIR/issue-109425.rs:5:4
+   |
+LL | fn is(_: u32, _: &str) {}
+   |    ^^ ------  -------
+help: remove the extra arguments
+   |
+LL -     is(1, (), "", ());
+LL +     is(1, "");
+   |
+
+error[E0061]: this function takes 1 argument but 3 arguments were supplied
+  --> $DIR/issue-109425.rs:22:5
+   |
 LL |     s(0, 1, "");     // s("")
    |     ^ -  - unexpected argument #2 of type `{integer}`
    |       |
@@ -93,6 +131,6 @@ LL -     s(0, 1, "");     // s("")
 LL +     s("");     // s("")
    |
 
-error: aborting due to 5 previous errors
+error: aborting due to 7 previous errors
 
 For more information about this error, try `rustc --explain E0061`.

tests/ui/argument-suggestions/issue-112507.stderr

@@ -18,8 +18,9 @@ LL |     Float(Option<f64>),
    |     ^^^^^
 help: remove the extra arguments
    |
-LL ~         ,
-LL ~         None);
+LL -         0,
+LL -         None,
+LL +         None);
    |
 
 error: aborting due to 1 previous error