Tweak invalid fn header and body parsing

* Recover empty `fn` bodies when encountering `}`
* Recover trailing `>` in return types
* Recover from non-type in array type `[<BAD TOKEN>; LEN]`

src/test/ui/issues/issue-39616.rs

@@ -1,4 +1,3 @@
 fn foo(a: [0; 1]) {} //~ ERROR expected type, found `0`
-//~| ERROR expected one of `)`, `,`, `->`, `;`, `where`, or `{`, found `]`
 
 fn main() {}

src/test/ui/issues/issue-39616.stderr

@@ -4,11 +4,5 @@ error: expected type, found `0`
 LL | fn foo(a: [0; 1]) {}
    |            ^ expected type
 
-error: expected one of `)`, `,`, `->`, `;`, `where`, or `{`, found `]`
-  --> $DIR/issue-39616.rs:1:16
-   |
-LL | fn foo(a: [0; 1]) {}
-   |                ^ expected one of `)`, `,`, `->`, `;`, `where`, or `{`
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 

src/test/ui/parser/issue-24780.rs

@@ -1,8 +1,9 @@
 // Verify that '>' is not both expected and found at the same time, as it used
 // to happen in #24780. For example, following should be an error:
-// expected one of ..., `>`, ... found `>`
+// expected one of ..., `>`, ... found `>`. No longer exactly this, but keeping for posterity.
 
-fn foo() -> Vec<usize>> {
-    //~^ ERROR expected one of `!`, `+`, `::`, `;`, `where`, or `{`, found `>`
+fn foo() -> Vec<usize>> { //~ ERROR unmatched angle bracket
     Vec::new()
 }
+
+fn main() {}

src/test/ui/parser/issue-24780.stderr

@@ -1,8 +1,8 @@
-error: expected one of `!`, `+`, `::`, `;`, `where`, or `{`, found `>`
+error: unmatched angle bracket
   --> $DIR/issue-24780.rs:5:23
    |
 LL | fn foo() -> Vec<usize>> {
-   |                       ^ expected one of `!`, `+`, `::`, `;`, `where`, or `{`
+   |                       ^^ help: remove extra angle bracket
 
 error: aborting due to previous error
 

src/test/ui/parser/issue-6610.stderr

@@ -2,11 +2,9 @@ error: expected one of `->`, `;`, `where`, or `{`, found `}`
   --> $DIR/issue-6610.rs:1:20
    |
 LL | trait Foo { fn a() }
-   |           -        ^
-   |           |        |
-   |           |        expected one of `->`, `;`, `where`, or `{`
-   |           |        the item list ends here
-   |           while parsing this item list starting here
+   |                -   ^ expected one of `->`, `;`, `where`, or `{`
+   |                |
+   |                while parsing this `fn`
 
 error: aborting due to previous error