Fix incorrect suggestion for extra argument with a type error

3 files changed, 171 insertions, 0 deletions

diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 63148ab517c..c6d72700b3f 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -951,6 +951,32 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             return err.emit();
         }
 
+        // Special case, we found an extra argument is provided, which is very common in practice.
+        // but there is a obviously better removing suggestion compared to the current one,
+        // try to find the argument with Error type, if we removed it all the types will become good,
+        // then we will replace the current suggestion.
+        if let [Error::Extra(provided_idx)] = &errors[..] {
+            let remove_idx_is_perfect = |idx: usize| -> bool {
+                let removed_arg_tys = provided_arg_tys
+                    .iter()
+                    .enumerate()
+                    .filter_map(|(j, arg)| if idx == j { None } else { Some(arg) })
+                    .collect::<IndexVec<ProvidedIdx, _>>();
+                std::iter::zip(formal_and_expected_inputs.iter(), removed_arg_tys.iter()).all(
+                    |((expected_ty, _), (provided_ty, _))| {
+                        !provided_ty.references_error()
+                            && self.can_coerce(*provided_ty, *expected_ty)
+                    },
+                )
+            };
+
+            if !remove_idx_is_perfect(provided_idx.as_usize()) {
+                if let Some(i) = (0..provided_args.len()).find(|&i| remove_idx_is_perfect(i)) {
+                    errors = vec![Error::Extra(ProvidedIdx::from_usize(i))];
+                }
+            }
+        }
+
         let mut err = if formal_and_expected_inputs.len() == provided_args.len() {
             struct_span_code_err!(
                 self.dcx(),
diff --git a/tests/ui/argument-suggestions/suggest-better-removing-issue-126246.rs b/tests/ui/argument-suggestions/suggest-better-removing-issue-126246.rs
new file mode 100644
index 00000000000..fa1802283c3
--- /dev/null
+++ b/tests/ui/argument-suggestions/suggest-better-removing-issue-126246.rs
@@ -0,0 +1,21 @@
+fn add_one(x: i32) -> i32 {
+    x + 1
+}
+
+fn add_two(x: i32, y: i32) -> i32 {
+    x + y
+}
+
+fn main() {
+    add_one(2, 2); //~ ERROR this function takes 1 argument but 2 arguments were supplied
+    add_one(no_such_local, 10); //~ ERROR cannot find value `no_such_local` in this scope
+    //~| ERROR this function takes 1 argument but 2 arguments were supplied
+    add_one(10, no_such_local); //~ ERROR cannot find value `no_such_local` in this scope
+    //~| ERROR this function takes 1 argument but 2 arguments were supplied
+    add_two(10, no_such_local, 10); //~ ERROR cannot find value `no_such_local` in this scope
+    //~| ERROR this function takes 2 arguments but 3 arguments were supplied
+    add_two(no_such_local, 10, 10); //~ ERROR cannot find value `no_such_local` in this scope
+    //~| ERROR this function takes 2 arguments but 3 arguments were supplied
+    add_two(10, 10, no_such_local); //~ ERROR cannot find value `no_such_local` in this scope
+    //~| ERROR this function takes 2 arguments but 3 arguments were supplied
+}
diff --git a/tests/ui/argument-suggestions/suggest-better-removing-issue-126246.stderr b/tests/ui/argument-suggestions/suggest-better-removing-issue-126246.stderr
new file mode 100644
index 00000000000..7c4daa3ffe9
--- /dev/null
+++ b/tests/ui/argument-suggestions/suggest-better-removing-issue-126246.stderr
@@ -0,0 +1,124 @@
+error[E0425]: cannot find value `no_such_local` in this scope
+  --> $DIR/suggest-better-removing-issue-126246.rs:11:13
+   |
+LL |     add_one(no_such_local, 10);
+   |             ^^^^^^^^^^^^^ not found in this scope
+
+error[E0425]: cannot find value `no_such_local` in this scope
+  --> $DIR/suggest-better-removing-issue-126246.rs:13:17
+   |
+LL |     add_one(10, no_such_local);
+   |                 ^^^^^^^^^^^^^ not found in this scope
+
+error[E0425]: cannot find value `no_such_local` in this scope
+  --> $DIR/suggest-better-removing-issue-126246.rs:15:17
+   |
+LL |     add_two(10, no_such_local, 10);
+   |                 ^^^^^^^^^^^^^ not found in this scope
+
+error[E0425]: cannot find value `no_such_local` in this scope
+  --> $DIR/suggest-better-removing-issue-126246.rs:17:13
+   |
+LL |     add_two(no_such_local, 10, 10);
+   |             ^^^^^^^^^^^^^ not found in this scope
+
+error[E0425]: cannot find value `no_such_local` in this scope
+  --> $DIR/suggest-better-removing-issue-126246.rs:19:21
+   |
+LL |     add_two(10, 10, no_such_local);
+   |                     ^^^^^^^^^^^^^ not found in this scope
+
+error[E0061]: this function takes 1 argument but 2 arguments were supplied
+  --> $DIR/suggest-better-removing-issue-126246.rs:10:5
+   |
+LL |     add_one(2, 2);
+   |     ^^^^^^^  ---
+   |              | |
+   |              | unexpected argument of type `{integer}`
+   |              help: remove the extra argument
+   |
+note: function defined here
+  --> $DIR/suggest-better-removing-issue-126246.rs:1:4
+   |
+LL | fn add_one(x: i32) -> i32 {
+   |    ^^^^^^^ ------
+
+error[E0061]: this function takes 1 argument but 2 arguments were supplied
+  --> $DIR/suggest-better-removing-issue-126246.rs:11:5
+   |
+LL |     add_one(no_such_local, 10);
+   |     ^^^^^^^ ---------------
+   |             |
+   |             unexpected argument
+   |             help: remove the extra argument
+   |
+note: function defined here
+  --> $DIR/suggest-better-removing-issue-126246.rs:1:4
+   |
+LL | fn add_one(x: i32) -> i32 {
+   |    ^^^^^^^ ------
+
+error[E0061]: this function takes 1 argument but 2 arguments were supplied
+  --> $DIR/suggest-better-removing-issue-126246.rs:13:5
+   |
+LL |     add_one(10, no_such_local);
+   |     ^^^^^^^   ---------------
+   |               | |
+   |               | unexpected argument
+   |               help: remove the extra argument
+   |
+note: function defined here
+  --> $DIR/suggest-better-removing-issue-126246.rs:1:4
+   |
+LL | fn add_one(x: i32) -> i32 {
+   |    ^^^^^^^ ------
+
+error[E0061]: this function takes 2 arguments but 3 arguments were supplied
+  --> $DIR/suggest-better-removing-issue-126246.rs:15:5
+   |
+LL |     add_two(10, no_such_local, 10);
+   |     ^^^^^^^   ---------------
+   |               | |
+   |               | unexpected argument
+   |               help: remove the extra argument
+   |
+note: function defined here
+  --> $DIR/suggest-better-removing-issue-126246.rs:5:4
+   |
+LL | fn add_two(x: i32, y: i32) -> i32 {
+   |    ^^^^^^^ ------  ------
+
+error[E0061]: this function takes 2 arguments but 3 arguments were supplied
+  --> $DIR/suggest-better-removing-issue-126246.rs:17:5
+   |
+LL |     add_two(no_such_local, 10, 10);
+   |     ^^^^^^^ ---------------
+   |             |
+   |             unexpected argument
+   |             help: remove the extra argument
+   |
+note: function defined here
+  --> $DIR/suggest-better-removing-issue-126246.rs:5:4
+   |
+LL | fn add_two(x: i32, y: i32) -> i32 {
+   |    ^^^^^^^ ------  ------
+
+error[E0061]: this function takes 2 arguments but 3 arguments were supplied
+  --> $DIR/suggest-better-removing-issue-126246.rs:19:5
+   |
+LL |     add_two(10, 10, no_such_local);
+   |     ^^^^^^^       ---------------
+   |                   | |
+   |                   | unexpected argument
+   |                   help: remove the extra argument
+   |
+note: function defined here
+  --> $DIR/suggest-better-removing-issue-126246.rs:5:4
+   |
+LL | fn add_two(x: i32, y: i32) -> i32 {
+   |    ^^^^^^^ ------  ------
+
+error: aborting due to 11 previous errors
+
+Some errors have detailed explanations: E0061, E0425.
+For more information about an error, try `rustc --explain E0061`.