Incorrect generic parameter ordering for E0747

[varkor]

https://github.com/rust-lang/rust/blob/a59264b01247836c70e24217e0d346b868387525/src/test/ui/suggestions/suggest-move-types.stderr#L121-L135
suggests type parameters should come before lifetime parameters, which is incorrect.
The message is emitted here:
https://github.com/rust-lang/rust/blob/a59264b01247836c70e24217e0d346b868387525/src/librustc_typeck/astconv.rs#L463-L477

This issue has been assigned to @camelid via this comment.

[camelid]

I want to try working on this.

@rustbot claim

[camelid]

I've been trying to fix this, but even reversing the arguments to the err.note format didn't seem to do anything. Am I missing something?

I also added ABC to the error note for testing:

err.note(&format!("{} arguments must be provided before {} arguments ABC", arg.descr(), kind));

And here's the error diff:

---- [ui] ui/suggestions/suggest-move-types.rs stdout ----
diff of stderr:

108	LL | struct Al<'a, T, M: OneWithLifetime<A=(), T, 'a>> {
109	   |                                           ^
110	   |
-	   = note: lifetime arguments must be provided before type arguments
+	   = note: type arguments must be provided before lifetime arguments ABC
112	
113	error[E0747]: type provided when a lifetime was expected
114	  --> $DIR/suggest-move-types.rs:48:71

116	LL | struct Bl<'a, 'b, 'c, T, U, V, M: ThreeWithLifetime<A=(), B=(), C=(), T, U, V, 'a, 'b, 'c>> {
117	   |                                                                       ^
118	   |
-	   = note: lifetime arguments must be provided before type arguments
+	   = note: type arguments must be provided before lifetime arguments ABC
120	
121	error[E0747]: lifetime provided when a type was expected
122	  --> $DIR/suggest-move-types.rs:65:56

124	LL | struct Cl<'a, 'b, 'c, T, U, V, M: ThreeWithLifetime<T, 'a, A=(), B=(), C=(), U, 'b, V, 'c>> {
125	   |                                                        ^^
126	   |
-	   = note: lifetime arguments must be provided before type arguments
+	   = note: lifetime arguments must be provided before type arguments ABC
128	
129	error[E0747]: lifetime provided when a type was expected
130	  --> $DIR/suggest-move-types.rs:82:56

132	LL | struct Dl<'a, 'b, 'c, T, U, V, M: ThreeWithLifetime<T, 'a, A=(), B=(), U, 'b, C=(), V, 'c>> {
133	   |                                                        ^^
134	   |
-	   = note: lifetime arguments must be provided before type arguments
+	   = note: lifetime arguments must be provided before type arguments ABC
136	
137	error: aborting due to 12 previous errors
138	


The actual stderr differed from the expected stderr.

EDIT: I modified the expected stderr for the test so that it matches how it should look after this is fixed by the way.

[camelid]

I've looked into it a bit more, and it looks like this isn't as simple as I thought at first. I thought it might work if I just reversed the arguments to format!, but that messes up other things.

I think I'll need to rethink this.

[varkor]

I've been trying to fix this, but even reversing the arguments to the err.note format didn't seem to do anything. Am I missing something?

Note that I cherry-picked the examples that were incorrect. The diagnostic is correct in other cases. You'll need to investigate a little to work out how best to fix this; one simple solution would be to sort the two with ParamKindOrd, though I'm not sure if that's the cleanest approach.

[camelid]

Okay, thanks for the info! I'll look into sorting and see if that works :)

[camelid]

I think I've figured out a basic solution. Let me know if there are things I can improve!