syntax: Introduce Ident::can_be_raw

src/test/ui/parser/raw/raw-literal-self.rs

@@ -1,3 +1,4 @@
-fn self_test(r#self: u32) {
-    //~^ ERROR `r#self` is not currently supported.
+fn main() {
+    let r#self;
+    //~^ ERROR `self` cannot be a raw identifier
 }

src/test/ui/parser/raw/raw-literal-self.stderr

@@ -1,8 +1,8 @@
-error: `r#self` is not currently supported.
-  --> $DIR/raw-literal-self.rs:1:14
+error: `self` cannot be a raw identifier
+  --> $DIR/raw-literal-self.rs:2:9
    |
-LL | fn self_test(r#self: u32) {
-   |              ^^^^^^
+LL |     let r#self;
+   |         ^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/parser/raw/raw-literal-underscore.rs

@@ -1,3 +1,4 @@
-fn underscore_test(r#_: u32) {
-    //~^ ERROR `r#_` is not currently supported.
+fn main() {
+    let r#_;
+    //~^ ERROR `_` cannot be a raw identifier
 }

src/test/ui/parser/raw/raw-literal-underscore.stderr

@@ -1,8 +1,8 @@
-error: `r#_` is not currently supported.
-  --> $DIR/raw-literal-underscore.rs:1:20
+error: `_` cannot be a raw identifier
+  --> $DIR/raw-literal-underscore.rs:2:9
    |
-LL | fn underscore_test(r#_: u32) {
-   |                    ^^^
+LL |     let r#_;
+   |         ^^^
 
 error: aborting due to previous error
 

src/test/ui/proc-macro/invalid-punct-ident-3.stderr

@@ -4,7 +4,7 @@ error: proc macro panicked
 LL | invalid_raw_ident!();
    | ^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: message: `"self"` is not a valid raw identifier
+   = help: message: `self` cannot be a raw identifier
 
 error: aborting due to previous error