Better method call error messages

compiler/rustc_errors/src/diagnostic.rs

@@ -307,6 +307,28 @@ impl Diagnostic {
         self
     }
 
+    /// Show a suggestion that has multiple parts to it, always as it's own subwindow.
+    /// In other words, multiple changes need to be applied as part of this suggestion.
+    pub fn multipart_suggestion_verbose(
+        &mut self,
+        msg: &str,
+        suggestion: Vec<(Span, String)>,
+        applicability: Applicability,
+    ) -> &mut Self {
+        self.suggestions.push(CodeSuggestion {
+            substitutions: vec![Substitution {
+                parts: suggestion
+                    .into_iter()
+                    .map(|(span, snippet)| SubstitutionPart { snippet, span })
+                    .collect(),
+            }],
+            msg: msg.to_owned(),
+            style: SuggestionStyle::ShowAlways,
+            applicability,
+        });
+        self
+    }
+
     /// Show multiple suggestions that have multiple parts.
     /// See also [`Diagnostic::multipart_suggestion()`].
     pub fn multipart_suggestions(

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -280,6 +280,20 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    /// See [`Diagnostic::multipart_suggestion_verbose()`].
+    pub fn multipart_suggestion_verbose(
+        &mut self,
+        msg: &str,
+        suggestion: Vec<(Span, String)>,
+        applicability: Applicability,
+    ) -> &mut Self {
+        if !self.0.allow_suggestions {
+            return self;
+        }
+        self.0.diagnostic.multipart_suggestion_verbose(msg, suggestion, applicability);
+        self
+    }
+
     /// See [`Diagnostic::multipart_suggestions()`].
     pub fn multipart_suggestions(
         &mut self,

compiler/rustc_typeck/src/check/expr.rs

@@ -221,7 +221,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         ty
     }
 
-    fn check_expr_kind(
+    pub(super) fn check_expr_kind(
         &self,
         expr: &'tcx hir::Expr<'tcx>,
         expected: Expectation<'tcx>,

src/test/ui/argument-suggestions/basic.rs

@@ -0,0 +1,25 @@
+// Some basic "obvious" cases for the heuristic error messages added for #65853
+// One for each of the detected cases
+
+enum E { X, Y }
+enum F { X2, Y2 }
+struct G {}
+struct H {}
+struct X {}
+struct Y {}
+struct Z {}
+
+
+fn invalid(_i: u32) {}
+fn extra() {}
+fn missing(_i: u32) {}
+fn swapped(_i: u32, _s: &str) {}
+fn permuted(_x: X, _y: Y, _z: Z) {}
+
+fn main() {
+    invalid(1.0); //~ ERROR arguments to this function are incorrect
+    extra(""); //~ ERROR arguments to this function are incorrect
+    missing(); //~ ERROR arguments to this function are incorrect
+    swapped("", 1); //~ ERROR arguments to this function are incorrect
+    permuted(Y {}, Z {}, X {}); //~ ERROR arguments to this function are incorrect
+}

src/test/ui/argument-suggestions/basic.stderr

@@ -0,0 +1,94 @@
+error[E0308]: arguments to this function are incorrect
+  --> $DIR/basic.rs:20:5
+   |
+LL |     invalid(1.0);
+   |     ^^^^^^^^---^
+   |             |
+   |             expected `u32`, found `{float}`
+   |
+note: function defined here
+  --> $DIR/basic.rs:13:4
+   |
+LL | fn invalid(_i: u32) {}
+   |    ^^^^^^^ -------
+help: provide an argument of the correct type
+   |
+LL |     invalid({u32});
+   |     ^^^^^^^^^^^^^^
+
+error[E0308]: arguments to this function are incorrect
+  --> $DIR/basic.rs:21:5
+   |
+LL |     extra("");
+   |     ^^^^^^--^
+   |           |
+   |           argument unexpected
+   |
+note: function defined here
+  --> $DIR/basic.rs:14:4
+   |
+LL | fn extra() {}
+   |    ^^^^^
+help: remove the extra argument
+   |
+LL |     extra();
+   |     ^^^^^^^
+
+error[E0308]: arguments to this function are incorrect
+  --> $DIR/basic.rs:22:5
+   |
+LL |     missing();
+   |     ^^^^^^^^^ an argument of type u32 is missing
+   |
+note: function defined here
+  --> $DIR/basic.rs:15:4
+   |
+LL | fn missing(_i: u32) {}
+   |    ^^^^^^^ -------
+help: provide the argument
+   |
+LL |     missing({u32});
+   |     ^^^^^^^^^^^^^^
+
+error[E0308]: arguments to this function are incorrect
+  --> $DIR/basic.rs:23:5
+   |
+LL |     swapped("", 1);
+   |     ^^^^^^^^--^^-^
+   |             |   |
+   |             |   expected `&str`,found `{integer}`
+   |             expected `u32`,found `&'static str`
+   |
+note: function defined here
+  --> $DIR/basic.rs:16:4
+   |
+LL | fn swapped(_i: u32, _s: &str) {}
+   |    ^^^^^^^ -------  --------
+help: swap these arguments
+   |
+LL |     swapped(1, "");
+   |     ^^^^^^^^^^^^^^
+
+error[E0308]: arguments to this function are incorrect
+  --> $DIR/basic.rs:24:5
+   |
+LL |     permuted(Y {}, Z {}, X {});
+   |     ^^^^^^^^^----^^----^^----^
+   |              |     |     |
+   |              |     |     expected `Z`,found `X`
+   |              |     expected `Y`,found `Z`
+   |              expected `X`,found `Y`
+   |
+note: function defined here
+  --> $DIR/basic.rs:17:4
+   |
+LL | fn permuted(_x: X, _y: Y, _z: Z) {}
+   |    ^^^^^^^^ -----  -----  -----
+help: reorder these arguments
+   |
+LL |     permuted(X {}, Y {}, Z {});
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/argument-suggestions/complex.rs

@@ -0,0 +1,16 @@
+// A complex case with mixed suggestions from #65853
+
+enum E { X, Y }
+enum F { X2, Y2 }
+struct G {}
+struct H {}
+struct X {}
+struct Y {}
+struct Z {}
+
+fn complex(_i: u32, _s: &str, _e: E, _f: F, _g: G, _x: X, _y: Y, _z: Z ) {}
+
+fn main() {
+  complex(1.0, H {}, &"", G{}, F::X2, Z {}, X {}, Y {});
+  //~^ ERROR arguments to this function are incorrect
+}

src/test/ui/argument-suggestions/complex.stderr

@@ -0,0 +1,19 @@
+error[E0308]: arguments to this function are incorrect
+  --> $DIR/complex.rs:14:3
+   |
+LL |   complex(1.0, H {}, &"", G{}, F::X2, Z {}, X {}, Y {});
+   |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: function defined here
+  --> $DIR/complex.rs:11:4
+   |
+LL | fn complex(_i: u32, _s: &str, _e: E, _f: F, _g: G, _x: X, _y: Y, _z: Z ) {}
+   |    ^^^^^^^ -------  --------  -----  -----  -----  -----  -----  ------
+help: did you mean
+   |
+LL |   complex({u32}, &"", {E}, F::X2, G{}, X {}, Y {}, Z {});
+   |   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/argument-suggestions/extra_arguments.rs

@@ -0,0 +1,35 @@
+fn empty() {}
+fn one_arg(_a: i32) {}
+fn two_arg_same(_a: i32, _b: i32) {}
+fn two_arg_diff(_a: i32, _b: &str) {}
+
+fn main() {
+  empty(""); //~ ERROR arguments to this function are incorrect
+
+  one_arg(1, 1); //~ ERROR arguments to this function are incorrect
+  one_arg(1, ""); //~ ERROR arguments to this function are incorrect
+  one_arg(1, "", 1.0); //~ ERROR arguments to this function are incorrect
+
+  two_arg_same(1, 1, 1); //~ ERROR arguments to this function are incorrect
+  two_arg_same(1, 1, 1.0); //~ ERROR arguments to this function are incorrect
+
+  two_arg_diff(1, 1, ""); //~ ERROR arguments to this function are incorrect
+  two_arg_diff(1, "", ""); //~ ERROR arguments to this function are incorrect
+  two_arg_diff(1, 1, "", ""); //~ ERROR arguments to this function are incorrect
+  two_arg_diff(1, "", 1, ""); //~ ERROR arguments to this function are incorrect
+
+  // Check with weird spacing and newlines
+  two_arg_same(1, 1,     ""); //~ ERROR arguments to this function are incorrect
+  two_arg_diff(1, 1,     ""); //~ ERROR arguments to this function are incorrect
+  two_arg_same( //~ ERROR arguments to this function are incorrect
+    1,
+    1,
+    ""
+  );
+
+  two_arg_diff( //~ ERROR arguments to this function are incorrect
+    1,
+    1,
+    ""
+  );
+}