Compare tuple element & arg types before suggesting a tuple

src/test/ui/suggestions/args-instead-of-tuple-errors.rs

@@ -0,0 +1,13 @@
+// Ensure we don't suggest tuple-wrapping when we'd end up with a type error
+
+fn main() {
+    // we shouldn't suggest to fix these - `2` isn't a `bool`
+
+    let _: Option<(i32, bool)> = Some(1, 2);
+    //~^ ERROR this enum variant takes 1 argument but 2 arguments were supplied
+    int_bool(1, 2);
+    //~^ ERROR this function takes 1 argument but 2 arguments were supplied
+}
+
+fn int_bool(_: (i32, bool)) {
+}

src/test/ui/suggestions/args-instead-of-tuple-errors.stderr

@@ -0,0 +1,25 @@
+error[E0061]: this enum variant takes 1 argument but 2 arguments were supplied
+  --> $DIR/args-instead-of-tuple-errors.rs:6:34
+   |
+LL |     let _: Option<(i32, bool)> = Some(1, 2);
+   |                                  ^^^^ -  - supplied 2 arguments
+   |                                  |
+   |                                  expected 1 argument
+
+error[E0061]: this function takes 1 argument but 2 arguments were supplied
+  --> $DIR/args-instead-of-tuple-errors.rs:8:5
+   |
+LL |     int_bool(1, 2);
+   |     ^^^^^^^^ -  - supplied 2 arguments
+   |     |
+   |     expected 1 argument
+   |
+note: function defined here
+  --> $DIR/args-instead-of-tuple-errors.rs:12:4
+   |
+LL | fn int_bool(_: (i32, bool)) {
+   |    ^^^^^^^^ --------------
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0061`.

src/test/ui/suggestions/args-instead-of-tuple.fixed

@@ -11,8 +11,8 @@ fn main() {
     let _: Option<()> = Some(());
     //~^ ERROR this enum variant takes 1 argument but 0 arguments were supplied
 
-    f((1, 2)); //~ ERROR this function takes 1 argument
+    two_ints((1, 2)); //~ ERROR this function takes 1 argument
 }
 
-fn f(_: (i32, i32)) {
+fn two_ints(_: (i32, i32)) {
 }

src/test/ui/suggestions/args-instead-of-tuple.rs

@@ -11,8 +11,8 @@ fn main() {
     let _: Option<()> = Some();
     //~^ ERROR this enum variant takes 1 argument but 0 arguments were supplied
 
-    f(1, 2); //~ ERROR this function takes 1 argument
+    two_ints(1, 2); //~ ERROR this function takes 1 argument
 }
 
-fn f(_: (i32, i32)) {
+fn two_ints(_: (i32, i32)) {
 }

src/test/ui/suggestions/args-instead-of-tuple.stderr

@@ -34,18 +34,18 @@ LL |     let _: Option<()> = Some(());
 error[E0061]: this function takes 1 argument but 2 arguments were supplied
   --> $DIR/args-instead-of-tuple.rs:14:5
    |
-LL |     f(1, 2);
-   |     ^ -  - supplied 2 arguments
+LL |     two_ints(1, 2);
+   |     ^^^^^^^^ -  - supplied 2 arguments
    |
 note: function defined here
   --> $DIR/args-instead-of-tuple.rs:17:4
    |
-LL | fn f(_: (i32, i32)) {
-   |    ^ -------------
+LL | fn two_ints(_: (i32, i32)) {
+   |    ^^^^^^^^ -------------
 help: use parentheses to construct a tuple
    |
-LL |     f((1, 2));
-   |       +    +
+LL |     two_ints((1, 2));
+   |              +    +
 
 error: aborting due to 4 previous errors