Rollup merge of #69201 - Aaron1011:feature/permit-if-attr, r=Centril

Permit attributes on 'if' expressions

Previously, attributes on 'if' expressions (e.g. `#[attr] if true {}`)
were disallowed during parsing. This made it impossible for macros to
perform any custom handling of such attributes (e.g. stripping them
away), since a compilation error would be emitted before they ever had a
chance to run.

This PR permits attributes on 'if' expressions ('if-attrs' from here on).
Both built-in attributes (e.g. `#[allow]`, `#[cfg]`) and proc-macro attributes are supported.

We still do *not* accept attributes on 'other parts' of an if-else
chain. That is, the following code snippet still fails to parse:

```rust
if true {} #[attr] else if false {} else #[attr] if false {} #[attr]
else {}
```

Closes https://github.com/rust-lang/rust/issues/68618

4 files changed, 37 insertions, 111 deletions

diff --git a/src/test/ui/parser/attr-stmt-expr-attr-bad.rs b/src/test/ui/parser/attr-stmt-expr-attr-bad.rs
index 118bff8144c..f3980a59648 100644
--- a/src/test/ui/parser/attr-stmt-expr-attr-bad.rs
+++ b/src/test/ui/parser/attr-stmt-expr-attr-bad.rs
@@ -38,8 +38,6 @@ fn main() {}
 //~^ ERROR an inner attribute is not permitted in this context
 #[cfg(FALSE)] fn e() { let _ = #[attr] &mut #![attr] 0; }
 //~^ ERROR an inner attribute is not permitted in this context
-#[cfg(FALSE)] fn e() { let _ = #[attr] if 0 {}; }
-//~^ ERROR attributes are not yet allowed on `if` expressions
 #[cfg(FALSE)] fn e() { let _ = if 0 #[attr] {}; }
 //~^ ERROR expected `{`, found `#`
 #[cfg(FALSE)] fn e() { let _ = if 0 {#![attr]}; }
@@ -51,14 +49,11 @@ fn main() {}
 #[cfg(FALSE)] fn e() { let _ = if 0 {} else {#![attr]}; }
 //~^ ERROR an inner attribute is not permitted in this context
 #[cfg(FALSE)] fn e() { let _ = if 0 {} else #[attr] if 0 {}; }
-//~^ ERROR attributes are not yet allowed on `if` expressions
-//~| ERROR expected `{`, found `#`
+//~^ ERROR expected `{`, found `#`
 #[cfg(FALSE)] fn e() { let _ = if 0 {} else if 0 #[attr] {}; }
 //~^ ERROR expected `{`, found `#`
 #[cfg(FALSE)] fn e() { let _ = if 0 {} else if 0 {#![attr]}; }
 //~^ ERROR an inner attribute is not permitted in this context
-#[cfg(FALSE)] fn e() { let _ = #[attr] if let _ = 0 {}; }
-//~^ ERROR attributes are not yet allowed on `if` expressions
 #[cfg(FALSE)] fn e() { let _ = if let _ = 0 #[attr] {}; }
 //~^ ERROR expected `{`, found `#`
 #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {#![attr]}; }
@@ -70,8 +65,7 @@ fn main() {}
 #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} else {#![attr]}; }
 //~^ ERROR an inner attribute is not permitted in this context
 #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} else #[attr] if let _ = 0 {}; }
-//~^ ERROR attributes are not yet allowed on `if` expressions
-//~| ERROR expected `{`, found `#`
+//~^ ERROR expected `{`, found `#`
 #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} else if let _ = 0 #[attr] {}; }
 //~^ ERROR expected `{`, found `#`
 #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} else if let _ = 0 {#![attr]}; }
diff --git a/src/test/ui/parser/attr-stmt-expr-attr-bad.stderr b/src/test/ui/parser/attr-stmt-expr-attr-bad.stderr
index 6159acd5080..4dcba27cb68 100644
--- a/src/test/ui/parser/attr-stmt-expr-attr-bad.stderr
+++ b/src/test/ui/parser/attr-stmt-expr-attr-bad.stderr
@@ -136,14 +136,8 @@ LL | #[cfg(FALSE)] fn e() { let _ = #[attr] &mut #![attr] 0; }
    |
    = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files. Outer attributes, like `#[test]`, annotate the item following them.
 
-error: attributes are not yet allowed on `if` expressions
-  --> $DIR/attr-stmt-expr-attr-bad.rs:41:32
-   |
-LL | #[cfg(FALSE)] fn e() { let _ = #[attr] if 0 {}; }
-   |                                ^^^^^^^
-
 error: expected `{`, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:43:37
+  --> $DIR/attr-stmt-expr-attr-bad.rs:41:37
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if 0 #[attr] {}; }
    |                                --   ^       --- help: try placing this code inside a block: `{ {}; }`
@@ -152,7 +146,7 @@ LL | #[cfg(FALSE)] fn e() { let _ = if 0 #[attr] {}; }
    |                                this `if` expression has a condition, but no block
 
 error: an inner attribute is not permitted in this context
-  --> $DIR/attr-stmt-expr-attr-bad.rs:45:38
+  --> $DIR/attr-stmt-expr-attr-bad.rs:43:38
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if 0 {#![attr]}; }
    |                                      ^^^^^^^^
@@ -160,13 +154,13 @@ LL | #[cfg(FALSE)] fn e() { let _ = if 0 {#![attr]}; }
    = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files. Outer attributes, like `#[test]`, annotate the item following them.
 
 error: expected one of `.`, `;`, `?`, `else`, or an operator, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:47:40
+  --> $DIR/attr-stmt-expr-attr-bad.rs:45:40
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if 0 {} #[attr] else {}; }
    |                                        ^ expected one of `.`, `;`, `?`, `else`, or an operator
 
 error: expected `{`, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:49:45
+  --> $DIR/attr-stmt-expr-attr-bad.rs:47:45
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if 0 {} else #[attr] {}; }
    |                                             ^       --- help: try placing this code inside a block: `{ {}; }`
@@ -174,21 +168,15 @@ LL | #[cfg(FALSE)] fn e() { let _ = if 0 {} else #[attr] {}; }
    |                                             expected `{`
 
 error: an inner attribute is not permitted in this context
-  --> $DIR/attr-stmt-expr-attr-bad.rs:51:46
+  --> $DIR/attr-stmt-expr-attr-bad.rs:49:46
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if 0 {} else {#![attr]}; }
    |                                              ^^^^^^^^
    |
    = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files. Outer attributes, like `#[test]`, annotate the item following them.
 
-error: attributes are not yet allowed on `if` expressions
-  --> $DIR/attr-stmt-expr-attr-bad.rs:53:45
-   |
-LL | #[cfg(FALSE)] fn e() { let _ = if 0 {} else #[attr] if 0 {}; }
-   |                                             ^^^^^^^
-
 error: expected `{`, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:53:45
+  --> $DIR/attr-stmt-expr-attr-bad.rs:51:45
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if 0 {} else #[attr] if 0 {}; }
    |                                             ^       -------- help: try placing this code inside a block: `{ if 0 {}; }`
@@ -196,7 +184,7 @@ LL | #[cfg(FALSE)] fn e() { let _ = if 0 {} else #[attr] if 0 {}; }
    |                                             expected `{`
 
 error: expected `{`, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:56:50
+  --> $DIR/attr-stmt-expr-attr-bad.rs:53:50
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if 0 {} else if 0 #[attr] {}; }
    |                                             --   ^       --- help: try placing this code inside a block: `{ {}; }`
@@ -205,21 +193,15 @@ LL | #[cfg(FALSE)] fn e() { let _ = if 0 {} else if 0 #[attr] {}; }
    |                                             this `if` expression has a condition, but no block
 
 error: an inner attribute is not permitted in this context
-  --> $DIR/attr-stmt-expr-attr-bad.rs:58:51
+  --> $DIR/attr-stmt-expr-attr-bad.rs:55:51
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if 0 {} else if 0 {#![attr]}; }
    |                                                   ^^^^^^^^
    |
    = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files. Outer attributes, like `#[test]`, annotate the item following them.
 
-error: attributes are not yet allowed on `if` expressions
-  --> $DIR/attr-stmt-expr-attr-bad.rs:60:32
-   |
-LL | #[cfg(FALSE)] fn e() { let _ = #[attr] if let _ = 0 {}; }
-   |                                ^^^^^^^
-
 error: expected `{`, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:62:45
+  --> $DIR/attr-stmt-expr-attr-bad.rs:57:45
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 #[attr] {}; }
    |                                --           ^       --- help: try placing this code inside a block: `{ {}; }`
@@ -228,7 +210,7 @@ LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 #[attr] {}; }
    |                                this `if` expression has a condition, but no block
 
 error: an inner attribute is not permitted in this context
-  --> $DIR/attr-stmt-expr-attr-bad.rs:64:46
+  --> $DIR/attr-stmt-expr-attr-bad.rs:59:46
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {#![attr]}; }
    |                                              ^^^^^^^^
@@ -236,13 +218,13 @@ LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {#![attr]}; }
    = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files. Outer attributes, like `#[test]`, annotate the item following them.
 
 error: expected one of `.`, `;`, `?`, `else`, or an operator, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:66:48
+  --> $DIR/attr-stmt-expr-attr-bad.rs:61:48
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} #[attr] else {}; }
    |                                                ^ expected one of `.`, `;`, `?`, `else`, or an operator
 
 error: expected `{`, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:68:53
+  --> $DIR/attr-stmt-expr-attr-bad.rs:63:53
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} else #[attr] {}; }
    |                                                     ^       --- help: try placing this code inside a block: `{ {}; }`
@@ -250,21 +232,15 @@ LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} else #[attr] {}; }
    |                                                     expected `{`
 
 error: an inner attribute is not permitted in this context
-  --> $DIR/attr-stmt-expr-attr-bad.rs:70:54
+  --> $DIR/attr-stmt-expr-attr-bad.rs:65:54
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} else {#![attr]}; }
    |                                                      ^^^^^^^^
    |
    = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files. Outer attributes, like `#[test]`, annotate the item following them.
 
-error: attributes are not yet allowed on `if` expressions
-  --> $DIR/attr-stmt-expr-attr-bad.rs:72:53
-   |
-LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} else #[attr] if let _ = 0 {}; }
-   |                                                     ^^^^^^^
-
 error: expected `{`, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:72:53
+  --> $DIR/attr-stmt-expr-attr-bad.rs:67:53
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} else #[attr] if let _ = 0 {}; }
    |                                                     ^       ---------------- help: try placing this code inside a block: `{ if let _ = 0 {}; }`
@@ -272,7 +248,7 @@ LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} else #[attr] if let _ = 0 {}
    |                                                     expected `{`
 
 error: expected `{`, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:75:66
+  --> $DIR/attr-stmt-expr-attr-bad.rs:69:66
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} else if let _ = 0 #[attr] {}; }
    |                                                     --           ^       --- help: try placing this code inside a block: `{ {}; }`
@@ -281,7 +257,7 @@ LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} else if let _ = 0 #[attr] {}
    |                                                     this `if` expression has a condition, but no block
 
 error: an inner attribute is not permitted in this context
-  --> $DIR/attr-stmt-expr-attr-bad.rs:77:67
+  --> $DIR/attr-stmt-expr-attr-bad.rs:71:67
    |
 LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} else if let _ = 0 {#![attr]}; }
    |                                                                   ^^^^^^^^
@@ -289,7 +265,7 @@ LL | #[cfg(FALSE)] fn e() { let _ = if let _ = 0 {} else if let _ = 0 {#![attr]}
    = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files. Outer attributes, like `#[test]`, annotate the item following them.
 
 error: an inner attribute is not permitted following an outer attribute
-  --> $DIR/attr-stmt-expr-attr-bad.rs:80:32
+  --> $DIR/attr-stmt-expr-attr-bad.rs:74:32
    |
 LL | #[cfg(FALSE)] fn s() { #[attr] #![attr] let _ = 0; }
    |                        ------- ^^^^^^^^ not permitted following an outer attribute
@@ -299,7 +275,7 @@ LL | #[cfg(FALSE)] fn s() { #[attr] #![attr] let _ = 0; }
    = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files. Outer attributes, like `#[test]`, annotate the item following them.
 
 error: an inner attribute is not permitted following an outer attribute
-  --> $DIR/attr-stmt-expr-attr-bad.rs:82:32
+  --> $DIR/attr-stmt-expr-attr-bad.rs:76:32
    |
 LL | #[cfg(FALSE)] fn s() { #[attr] #![attr] 0; }
    |                        ------- ^^^^^^^^ not permitted following an outer attribute
@@ -309,7 +285,7 @@ LL | #[cfg(FALSE)] fn s() { #[attr] #![attr] 0; }
    = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files. Outer attributes, like `#[test]`, annotate the item following them.
 
 error: an inner attribute is not permitted following an outer attribute
-  --> $DIR/attr-stmt-expr-attr-bad.rs:84:32
+  --> $DIR/attr-stmt-expr-attr-bad.rs:78:32
    |
 LL | #[cfg(FALSE)] fn s() { #[attr] #![attr] foo!(); }
    |                        ------- ^^^^^^^^ not permitted following an outer attribute
@@ -319,7 +295,7 @@ LL | #[cfg(FALSE)] fn s() { #[attr] #![attr] foo!(); }
    = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files. Outer attributes, like `#[test]`, annotate the item following them.
 
 error: an inner attribute is not permitted following an outer attribute
-  --> $DIR/attr-stmt-expr-attr-bad.rs:86:32
+  --> $DIR/attr-stmt-expr-attr-bad.rs:80:32
    |
 LL | #[cfg(FALSE)] fn s() { #[attr] #![attr] foo![]; }
    |                        ------- ^^^^^^^^ not permitted following an outer attribute
@@ -329,7 +305,7 @@ LL | #[cfg(FALSE)] fn s() { #[attr] #![attr] foo![]; }
    = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files. Outer attributes, like `#[test]`, annotate the item following them.
 
 error: an inner attribute is not permitted following an outer attribute
-  --> $DIR/attr-stmt-expr-attr-bad.rs:88:32
+  --> $DIR/attr-stmt-expr-attr-bad.rs:82:32
    |
 LL | #[cfg(FALSE)] fn s() { #[attr] #![attr] foo!{}; }
    |                        ------- ^^^^^^^^ not permitted following an outer attribute
@@ -339,7 +315,7 @@ LL | #[cfg(FALSE)] fn s() { #[attr] #![attr] foo!{}; }
    = note: inner attributes, like `#![no_std]`, annotate the item enclosing them, and are usually found at the beginning of source files. Outer attributes, like `#[test]`, annotate the item following them.
 
 error[E0586]: inclusive range with no end
-  --> $DIR/attr-stmt-expr-attr-bad.rs:94:35
+  --> $DIR/attr-stmt-expr-attr-bad.rs:88:35
    |
 LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] 10 => () } }
    |                                   ^^^ help: use `..` instead
@@ -347,13 +323,13 @@ LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] 10 => () } }
    = note: inclusive ranges must be bounded at the end (`..=b` or `a..=b`)
 
 error: expected one of `=>`, `if`, or `|`, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:94:38
+  --> $DIR/attr-stmt-expr-attr-bad.rs:88:38
    |
 LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] 10 => () } }
    |                                      ^ expected one of `=>`, `if`, or `|`
 
 error[E0586]: inclusive range with no end
-  --> $DIR/attr-stmt-expr-attr-bad.rs:97:35
+  --> $DIR/attr-stmt-expr-attr-bad.rs:91:35
    |
 LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] -10 => () } }
    |                                   ^^^ help: use `..` instead
@@ -361,19 +337,19 @@ LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] -10 => () } }
    = note: inclusive ranges must be bounded at the end (`..=b` or `a..=b`)
 
 error: expected one of `=>`, `if`, or `|`, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:97:38
+  --> $DIR/attr-stmt-expr-attr-bad.rs:91:38
    |
 LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] -10 => () } }
    |                                      ^ expected one of `=>`, `if`, or `|`
 
 error: unexpected token: `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:100:39
+  --> $DIR/attr-stmt-expr-attr-bad.rs:94:39
    |
 LL | #[cfg(FALSE)] fn e() { match 0 { 0..=-#[attr] 10 => () } }
    |                                       ^
 
 error[E0586]: inclusive range with no end
-  --> $DIR/attr-stmt-expr-attr-bad.rs:102:35
+  --> $DIR/attr-stmt-expr-attr-bad.rs:96:35
    |
 LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] FOO => () } }
    |                                   ^^^ help: use `..` instead
@@ -381,47 +357,47 @@ LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] FOO => () } }
    = note: inclusive ranges must be bounded at the end (`..=b` or `a..=b`)
 
 error: expected one of `=>`, `if`, or `|`, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:102:38
+  --> $DIR/attr-stmt-expr-attr-bad.rs:96:38
    |
 LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] FOO => () } }
    |                                      ^ expected one of `=>`, `if`, or `|`
 
 error: unexpected token: `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:106:34
+  --> $DIR/attr-stmt-expr-attr-bad.rs:100:34
    |
 LL | #[cfg(FALSE)] fn e() { let _ = x.#![attr]foo(); }
    |                                  ^
 
 error: expected one of `.`, `;`, `?`, or an operator, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:106:34
+  --> $DIR/attr-stmt-expr-attr-bad.rs:100:34
    |
 LL | #[cfg(FALSE)] fn e() { let _ = x.#![attr]foo(); }
    |                                  ^ expected one of `.`, `;`, `?`, or an operator
 
 error: unexpected token: `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:109:34
+  --> $DIR/attr-stmt-expr-attr-bad.rs:103:34
    |
 LL | #[cfg(FALSE)] fn e() { let _ = x.#[attr]foo(); }
    |                                  ^
 
 error: expected one of `.`, `;`, `?`, or an operator, found `#`
-  --> $DIR/attr-stmt-expr-attr-bad.rs:109:34
+  --> $DIR/attr-stmt-expr-attr-bad.rs:103:34
    |
 LL | #[cfg(FALSE)] fn e() { let _ = x.#[attr]foo(); }
    |                                  ^ expected one of `.`, `;`, `?`, or an operator
 
 error: expected statement after outer attribute
-  --> $DIR/attr-stmt-expr-attr-bad.rs:114:37
+  --> $DIR/attr-stmt-expr-attr-bad.rs:108:37
    |
 LL | #[cfg(FALSE)] fn e() { { fn foo() { #[attr]; } } }
    |                                     ^^^^^^^
 
 error: expected statement after outer attribute
-  --> $DIR/attr-stmt-expr-attr-bad.rs:116:37
+  --> $DIR/attr-stmt-expr-attr-bad.rs:110:37
    |
 LL | #[cfg(FALSE)] fn e() { { fn foo() { #[attr] } } }
    |                                     ^^^^^^^
 
-error: aborting due to 57 previous errors
+error: aborting due to 53 previous errors
 
 For more information about this error, try `rustc --explain E0586`.
diff --git a/src/test/ui/parser/recovery-attr-on-if.rs b/src/test/ui/parser/recovery-attr-on-if.rs
deleted file mode 100644
index 0d1f5be7b49..00000000000
--- a/src/test/ui/parser/recovery-attr-on-if.rs
+++ /dev/null
@@ -1,9 +0,0 @@
-fn main() {
-    #[attr] if true {};
-    //~^ ERROR cannot find attribute
-    //~| ERROR attributes are not yet allowed on `if` expressions
-    #[attr] if true {};
-    //~^ ERROR cannot find attribute
-    //~| ERROR attributes are not yet allowed on `if` expressions
-    let _recovery_witness: () = 0; //~ ERROR mismatched types
-}
diff --git a/src/test/ui/parser/recovery-attr-on-if.stderr b/src/test/ui/parser/recovery-attr-on-if.stderr
deleted file mode 100644
index a02846827c9..00000000000
--- a/src/test/ui/parser/recovery-attr-on-if.stderr
+++ /dev/null
@@ -1,35 +0,0 @@
-error: attributes are not yet allowed on `if` expressions
-  --> $DIR/recovery-attr-on-if.rs:2:5
-   |
-LL |     #[attr] if true {};
-   |     ^^^^^^^
-
-error: attributes are not yet allowed on `if` expressions
-  --> $DIR/recovery-attr-on-if.rs:5:5
-   |
-LL |     #[attr] if true {};
-   |     ^^^^^^^
-
-error: cannot find attribute `attr` in this scope
-  --> $DIR/recovery-attr-on-if.rs:5:7
-   |
-LL |     #[attr] if true {};
-   |       ^^^^
-
-error: cannot find attribute `attr` in this scope
-  --> $DIR/recovery-attr-on-if.rs:2:7
-   |
-LL |     #[attr] if true {};
-   |       ^^^^
-
-error[E0308]: mismatched types
-  --> $DIR/recovery-attr-on-if.rs:8:33
-   |
-LL |     let _recovery_witness: () = 0;
-   |                            --   ^ expected `()`, found integer
-   |                            |
-   |                            expected due to this
-
-error: aborting due to 5 previous errors
-
-For more information about this error, try `rustc --explain E0308`.