Properly suggest deref in else block

[mibac138]

Fixes #79736

[rust-highfive]

r? @ecstatic-morse

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[rust-log-analyzer]

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---
Building wheels for collected packages: PyYAML
  Running setup.py bdist_wheel for PyYAML: started
  Running setup.py bdist_wheel for PyYAML: finished with status 'error'
  Failed building wheel for PyYAML
  Complete output from command /usr/bin/python3 -u -c "import setuptools, tokenize;__file__='/tmp/pip-build-0nvokodb/PyYAML/setup.py';f=getattr(tokenize, 'open', open)(__file__);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, __file__, 'exec'))" bdist_wheel -d /tmp/tmpy1hcq06opip-wheel- --python-tag cp36:
     or: -c --help [cmd1 cmd2 ...]
     or: -c --help-commands
     or: -c cmd --help
  
---
configure: rust.channel         := nightly
configure: rust.debug-assertions := True
configure: llvm.assertions      := True
configure: dist.missing-tools   := True
configure: build.configure-args := ['--enable-sccache', '--disable-manage-submodu ...
configure: writing `config.toml` in current directory
configure: 
configure: run `python /checkout/x.py --help`
configure: 
---
skip untracked path cpu-usage.csv during rustfmt invocations
skip untracked path src/doc/book/ during rustfmt invocations
skip untracked path src/doc/rust-by-example/ during rustfmt invocations
skip untracked path src/llvm-project/ during rustfmt invocations
Diff in /checkout/compiler/rustc_typeck/src/check/demand.rs at line 360:
     }
 
 
-    crate fn hir_id_sole_block_element(
-        &self,
-        hir_id: hir::HirId,
-    ) -> Option<&'tcx hir::Expr<'tcx>> {
+    crate fn hir_id_sole_block_element(&self, hir_id: hir::HirId) -> Option<&'tcx hir::Expr<'tcx>> {
         match self.tcx.hir().find(hir_id)? {
-            Node::Expr(hir::Expr {
-                kind: hir::ExprKind::Block(block, ..),
-                ..
-            }) => block.expr,
+            Node::Expr(hir::Expr { kind: hir::ExprKind::Block(block, ..), .. }) => block.expr,
             _ => None,
     }
     }
Running `"/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/rustfmt" "--config-path" "/checkout" "--edition" "2018" "--unstable-features" "--skip-children" "--check" "/checkout/compiler/rustc_typeck/src/check/demand.rs"` failed.
If you're running `tidy`, try again with `--bless`. Or, if you just want to format code, run `./x.py fmt` instead.
Build completed unsuccessfully in 0:00:16
== clock drift check ==
  local time: Thu Dec 17 12:44:28 UTC 2020
  network time: Thu, 17 Dec 2020 00:13:25 GMT

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[camelid]

r? @davidtwco maybe?

[camelid]

Can you add a test for this as well?

fn main() {
    let a = &1;
    let b = &2;
    let val = if true {
        *a
    } else if true {
        b
    } else {
        &0
    };
}

Current output:

error[E0308]: `if` and `else` have incompatible types
  --> src/main.rs:6:12
   |
4  |        let val = if true {
   |   _______________-
5  |  |         *a
   |  |         -- expected because of this
6  |  |     } else if true {
   |  |____________^
7  | ||         b
8  | ||     } else {
9  | ||         &0
10 | ||     };
   | ||     ^
   | ||_____|
   | |______`if` and `else` have incompatible types
   |        expected integer, found `&{integer}`
   |
help: consider dereferencing the borrow
   |
6  |     } else *if true {
7  |         b
8  |     } else {
9  |         &0
10 |     };
   |

[davidtwco]

Could you also add the test requested by @camelid?

[davidtwco]

Suggested change

	crate fn hir_id_sole_block_element(&self, hir_id: hir::HirId) -> Option<&'tcx hir::Expr<'tcx>> {
	crate fn maybe_get_block_expr(&self, hir_id: hir::HirId) -> Option<&'tcx hir::Expr<'tcx>> {

Could you add a doc comment too?

[JohnCSimon]

@mibac138 Ping from triage can you please address the comments from the reviewer?

[crlf0710]

@mibac138 Ping from triage: any updates on this?

[JohnCSimon]

Triage:
@mibac138 - closing this due to inactivity, please feel free to reopen when you're ready to continue.

[LeSeulArtichaut]

I can push this to the finish line