Rollup merge of #109203 - Ezrashaw:refactor-ident-parsing, r=Nilstrieb

refactor/feat: refactor identifier parsing a bit

\+ error recovery for `expected_ident_found`

Prior art: #108854

tests/ui/parser/ident-recovery.rs

@@ -0,0 +1,16 @@
+fn ,comma() {
+    //~^ ERROR expected identifier, found `,`
+    struct Foo {
+        x: i32,,
+        //~^ ERROR expected identifier, found `,`
+        y: u32,
+    }
+}
+
+fn break() {
+//~^ ERROR expected identifier, found keyword `break`
+    let continue = 5;
+    //~^ ERROR expected identifier, found keyword `continue`
+}
+
+fn main() {}

tests/ui/parser/ident-recovery.stderr

@@ -0,0 +1,42 @@
+error: expected identifier, found `,`
+  --> $DIR/ident-recovery.rs:1:4
+   |
+LL | fn ,comma() {
+   |    ^
+   |    |
+   |    expected identifier
+   |    help: remove this comma
+
+error: expected identifier, found `,`
+  --> $DIR/ident-recovery.rs:4:16
+   |
+LL |         x: i32,,
+   |                ^
+   |                |
+   |                expected identifier
+   |                help: remove this comma
+
+error: expected identifier, found keyword `break`
+  --> $DIR/ident-recovery.rs:10:4
+   |
+LL | fn break() {
+   |    ^^^^^ expected identifier, found keyword
+   |
+help: escape `break` to use it as an identifier
+   |
+LL | fn r#break() {
+   |    ++
+
+error: expected identifier, found keyword `continue`
+  --> $DIR/ident-recovery.rs:12:9
+   |
+LL |     let continue = 5;
+   |         ^^^^^^^^ expected identifier, found keyword
+   |
+help: escape `continue` to use it as an identifier
+   |
+LL |     let r#continue = 5;
+   |         ++
+
+error: aborting due to 4 previous errors
+

tests/ui/parser/integer-literal-start-ident.stderr

@@ -4,7 +4,11 @@ error: expected identifier, found `1main`
 LL | fn 1main() {}
    |    ^^^^^ expected identifier
    |
-   = help: identifiers cannot start with a number
+help: identifiers cannot start with a number
+  --> $DIR/integer-literal-start-ident.rs:1:4
+   |
+LL | fn 1main() {}
+   |    ^
 
 error: aborting due to previous error
 

tests/ui/parser/issues/issue-104088.rs

@@ -1,26 +1,19 @@
-fn test() {
+fn 1234test() {
+//~^ ERROR expected identifier, found `1234test`
     if let 123 = 123 { println!("yes"); }
-}
 
-fn test_2() {
+    if let 2e1 = 123 {
+        //~^ ERROR mismatched types
+    }
+
+    let 23name = 123;
+    //~^ ERROR expected identifier, found `23name`
+
+    let 2x: i32 = 123;
+    //~^ ERROR expected identifier, found `2x`
+
     let 1x = 123;
     //~^ ERROR expected identifier, found `1x`
 }
 
-fn test_3() {
-    let 2x: i32 = 123;
-    //~^ ERROR expected identifier, found `2x`
-}
-
-fn test_4() {
-    if let 2e1 = 123 {
-        //~^ ERROR mismatched types
-    }
-}
-
-fn test_5() {
-    let 23name = 123;
-    //~^ ERROR expected identifier, found `23name`
-}
-
 fn main() {}

tests/ui/parser/issues/issue-104088.stderr

@@ -1,35 +1,59 @@
-error: expected identifier, found `1x`
-  --> $DIR/issue-104088.rs:6:9
+error: expected identifier, found `1234test`
+  --> $DIR/issue-104088.rs:1:4
    |
-LL |     let 1x = 123;
-   |         ^^ expected identifier
+LL | fn 1234test() {
+   |    ^^^^^^^^ expected identifier
    |
-   = help: identifiers cannot start with a number
-
-error: expected identifier, found `2x`
-  --> $DIR/issue-104088.rs:11:9
+help: identifiers cannot start with a number
+  --> $DIR/issue-104088.rs:1:4
    |
-LL |     let 2x: i32 = 123;
-   |         ^^ expected identifier
-   |
-   = help: identifiers cannot start with a number
+LL | fn 1234test() {
+   |    ^^^^
 
 error: expected identifier, found `23name`
-  --> $DIR/issue-104088.rs:22:9
+  --> $DIR/issue-104088.rs:9:9
    |
 LL |     let 23name = 123;
    |         ^^^^^^ expected identifier
    |
-   = help: identifiers cannot start with a number
+help: identifiers cannot start with a number
+  --> $DIR/issue-104088.rs:9:9
+   |
+LL |     let 23name = 123;
+   |         ^^
+
+error: expected identifier, found `2x`
+  --> $DIR/issue-104088.rs:12:9
+   |
+LL |     let 2x: i32 = 123;
+   |         ^^ expected identifier
+   |
+help: identifiers cannot start with a number
+  --> $DIR/issue-104088.rs:12:9
+   |
+LL |     let 2x: i32 = 123;
+   |         ^
+
+error: expected identifier, found `1x`
+  --> $DIR/issue-104088.rs:15:9
+   |
+LL |     let 1x = 123;
+   |         ^^ expected identifier
+   |
+help: identifiers cannot start with a number
+  --> $DIR/issue-104088.rs:15:9
+   |
+LL |     let 1x = 123;
+   |         ^
 
 error[E0308]: mismatched types
-  --> $DIR/issue-104088.rs:16:12
+  --> $DIR/issue-104088.rs:5:12
    |
 LL |     if let 2e1 = 123 {
    |            ^^^   --- this expression has type `{integer}`
    |            |
    |            expected integer, found floating-point number
 
-error: aborting due to 4 previous errors
+error: aborting due to 5 previous errors
 
 For more information about this error, try `rustc --explain E0308`.