Auto merge of #61331 - estebank:fn-arg-parse-recovery, r=varkor

Recover gracefully from argument with missing type or param name

src/test/ui/parser/inverted-parameters.rs

@@ -20,6 +20,8 @@ fn pattern((i32, i32) (a, b)) {}
 
 fn fizz(i32) {}
 //~^ ERROR expected one of `:` or `@`
+//~| HELP if this was a parameter name, give it a type
+//~| HELP if this is a type, explicitly ignore the parameter name
 
 fn missing_colon(quux S) {}
 //~^ ERROR expected one of `:` or `@`

src/test/ui/parser/inverted-parameters.stderr

@@ -33,9 +33,19 @@ error: expected one of `:` or `@`, found `)`
    |
 LL | fn fizz(i32) {}
    |            ^ expected one of `:` or `@` here
+   |
+   = note: anonymous parameters are removed in the 2018 edition (see RFC 1685)
+help: if this was a parameter name, give it a type
+   |
+LL | fn fizz(i32: TypeName) {}
+   |         ^^^^^^^^^^^^^
+help: if this is a type, explicitly ignore the parameter name
+   |
+LL | fn fizz(_: i32) {}
+   |         ^^^^^^
 
 error: expected one of `:` or `@`, found `S`
-  --> $DIR/inverted-parameters.rs:24:23
+  --> $DIR/inverted-parameters.rs:26:23
    |
 LL | fn missing_colon(quux S) {}
    |                  -----^

src/test/ui/parser/omitted-arg-in-item-fn.stderr

@@ -3,6 +3,16 @@ error: expected one of `:` or `@`, found `)`
    |
 LL | fn foo(x) {
    |         ^ expected one of `:` or `@` here
+   |
+   = note: anonymous parameters are removed in the 2018 edition (see RFC 1685)
+help: if this was a parameter name, give it a type
+   |
+LL | fn foo(x: TypeName) {
+   |        ^^^^^^^^^^^
+help: if this is a type, explicitly ignore the parameter name
+   |
+LL | fn foo(_: x) {
+   |        ^^^^
 
 error: aborting due to previous error