Auto merge of #39485 - canndrew:inference-fix-39297, r=nikomatsakis

Ignore expected type in diverging blocks

As per comment: #39297 (comment)

Author: bors

src/librustc_typeck/check/mod.rs

@@ -4156,17 +4156,6 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         };
 
         if self.diverges.get().always() {
-            if let ExpectHasType(ety) = expected {
-                // Avoid forcing a type (only `!` for now) in unreachable code.
-                // FIXME(aburka) do we need this special case? and should it be is_uninhabited?
-                if !ety.is_never() {
-                    if let Some(ref e) = blk.expr {
-                        // Coerce the tail expression to the right type.
-                        self.demand_coerce(e, ty, ety);
-                    }
-                }
-            }
-
             ty = self.next_diverging_ty_var(TypeVariableOrigin::DivergingBlockExpr(blk.span));
         } else if let ExpectHasType(ety) = expected {
             if let Some(ref e) = blk.expr {

src/test/compile-fail/issue-5500.rs

@@ -8,12 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+fn g() {
+    &panic!()
+}
+
 fn f() -> isize {
     (return 1, return 2)
-//~^ ERROR mismatched types
-//~| expected type `isize`
-//~| found type `(_, _)`
-//~| expected isize, found tuple
 }
 
 fn main() {}

src/test/compile-fail/issue-10176.rs renamed to src/test/run-pass/inference-changes-39485.rs

@@ -8,7 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![allow(unknown_features)]
+#![allow(unused_features)]
+#![allow(unreachable_code)]
 #![feature(box_syntax)]
 
 #[derive(PartialEq, Debug)]
@@ -28,14 +29,14 @@ struct Foo {
 }
 
 fn foo() -> Result<Foo, isize> {
-    return Ok(Foo {
+    return Ok::<Foo, isize>(Foo {
         x: Bar { x: 22 },
         a: return Err(32)
     });
 }
 
 fn baz() -> Result<Foo, isize> {
-    Ok(Foo {
+    Ok::<Foo, isize>(Foo {
         x: Bar { x: 22 },
         a: return Err(32)
     })

src/test/run-pass/issue-15763.rs

@@ -11,6 +11,8 @@
 // A regression test extracted from image-0.3.11. The point of
 // failure was in `index_colors` below.
 
+#![allow(unused)]
+
 use std::ops::{Deref, DerefMut};
 
 #[derive(Copy, Clone)]
@@ -92,7 +94,7 @@ pub fn index_colors<Pix>(image: &ImageBuffer<Pix, Vec<u8>>)
                          -> ImageBuffer<Luma<u8>, Vec<u8>>
 where Pix: Pixel<Subpixel=u8> + 'static,
 {
-    let mut indices: ImageBuffer<_,Vec<_>> = loop { };
+    let mut indices: ImageBuffer<Luma<u8>, Vec<u8>> = loop { };
     for (pixel, idx) in image.pixels().zip(indices.pixels_mut()) {
         // failured occurred here ^^ because we were requiring that we
         // could project Pixel or Subpixel from `T_indices` (type of