Better method call error messages

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 +1,87 @@
+error[E0059]: arguments to this function are incorrect
+  --> $DIR/basic.rs:20:13
+   |
+LL |     invalid(1.0);
+   |             ^^^ expected u32, found {float}
+   |
+note: function defined here
+  --> $DIR/basic.rs:13:4
+   |
+LL | fn invalid(_i: u32) {}
+   |    ^^^^^^^ -------
+help: provideing a parameter of the correct type here may help
+   |
+LL |     invalid({u32});
+   |             ^^^^^
+
+error[E0059]: arguments to this function are incorrect
+  --> $DIR/basic.rs:21:11
+   |
+LL |     extra("");
+   |           ^^
+   |           |
+   |           this parameter of type &'static str isn't needed for extra
+   |           help: removing this argument may help
+   |
+note: function defined here
+  --> $DIR/basic.rs:14:4
+   |
+LL | fn extra() {}
+   |    ^^^^^
+
+error[E0059]: arguments to this function are incorrect
+  --> $DIR/basic.rs:22:13
+   |
+LL |     missing();
+   |             ^ missing argument of type u32
+   |
+note: function defined here
+  --> $DIR/basic.rs:15:4
+   |
+LL | fn missing(_i: u32) {}
+   |    ^^^^^^^ -------
+help: provideing a parameter of the correct type here may help
+   |
+LL |     missing( {u32},);
+   |              ^^^^^^
+
+error[E0059]: arguments to this function are incorrect
+  --> $DIR/basic.rs:23:13
+   |
+LL |     swapped("", 1);
+   |             ^^  ^ expected &str, found &str
+   |             |
+   |             expected u32, found u32
+   |
+note: function defined here
+  --> $DIR/basic.rs:16:4
+   |
+LL | fn swapped(_i: u32, _s: &str) {}
+   |    ^^^^^^^ -------  --------
+help: swapping these two arguments might help
+   |
+LL |     swapped(1, "");
+   |             ^  ^^
+
+error[E0059]: arguments to this function are incorrect
+  --> $DIR/basic.rs:24:14
+   |
+LL |     permuted(Y {}, Z {}, X {});
+   |              ^^^^  ^^^^  ^^^^ expected Z, found Z
+   |              |     |
+   |              |     expected Y, found Y
+   |              expected X, found X
+   |
+note: function defined here
+  --> $DIR/basic.rs:17:4
+   |
+LL | fn permuted(_x: X, _y: Y, _z: Z) {}
+   |    ^^^^^^^^ -----  -----  -----
+help: reordering these parameters might help
+   |
+LL |     permuted(X {}, Y {}, Z {});
+   |              ^^^^  ^^^^  ^^^^
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0059`.

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 +1,27 @@
+error[E0059]: multiple arguments to this function are incorrect
+  --> $DIR/complex.rs:14:11
+   |
+LL |   complex(1.0, H {}, &"", G{}, F::X2, Z {}, X {}, Y {});
+   |           ^^^  ^^^^      ^^^^  ^^^^^  ^^^^  ^^^^  ^^^^ expected Z, found Z
+   |           |    |         ||    |      |     |
+   |           |    |         ||    |      |     expected Y, found Y
+   |           |    |         ||    |      expected X, found X
+   |           |    |         ||    expected G, found G
+   |           |    |         |expected F, found F
+   |           |    |         missing argument of type E
+   |           |    this parameter of type H isn't needed for complex
+   |           expected u32, found {float}
+   |
+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: the following changes might help
+   |
+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 E0059`.

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(
+    1,
+    1,
+    "" //~ ERROR arguments to this function are incorrect
+  );
+
+  two_arg_diff(
+    1,
+    1, //~ ERROR arguments to this function are incorrect
+    ""
+  );
+}