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Resolve infered types when complaining about unexpected call type #89202

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Merged
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Oct 1, 2021
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Resolve infered types when complaining about unexpected call type #89202

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Add test
estebank Sep 23, 2021
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Resolve infered types when complaining about unexpected call type
estebank Sep 23, 2021
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1 change: 1 addition & 0 deletions compiler/rustc_typeck/src/check/callee.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -350,6 +350,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
}

let callee_ty = self.resolve_vars_if_possible(callee_ty);
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I wonder why callee_ty is an TyVar and not an IntVar, I think we should dig into this a bit instead of just patching up the diagnostic

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I'm guessing the TyVar is coming from the {} block's tail expression not having unified yet?

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If that were the case, wouldn't we also see the tyvar, when using a function type?

I think we're doing something odd when type checking the literal expression.

I'm currently somewhere deep in that code anyway, I'll check and post my findings

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Yea, you're right. The tail block expression will fall back to a type variable in case we don't know anything about the type. This happens in

rust/compiler/rustc_typeck/src/check/expectation.rs

Line 119 in 3982ac2

fcx.next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::MiscVariable, span })

So... I guess we can't avoid this at creation time. oh well...

let mut err = type_error_struct!(
self.tcx.sess,
callee_expr.span,
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3 changes: 3 additions & 0 deletions src/test/ui/typeck/call-block.rs
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@@ -0,0 +1,3 @@
fn main() {
let _ = {42}(); //~ ERROR expected function, found `{integer}`
}
11 changes: 11 additions & 0 deletions src/test/ui/typeck/call-block.stderr
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@@ -0,0 +1,11 @@
error[E0618]: expected function, found `{integer}`
--> $DIR/call-block.rs:2:13
|
LL | let _ = {42}();
| ^^^^--
| |
| call expression requires function

error: aborting due to previous error

For more information about this error, try `rustc --explain E0618`.