While parsing enum variant, the error message always disappear

Because the error message that emit out is from main error of parser
The information of enum variant disappears while parsing enum variant with error
We only check the syntax of expecting token, i.e, in case #103869
It will error it without telling the message that this error is from pasring enum variant.
Propagate the sub-error from parsing enum variant to the main error of parser by chaining it with map_err
Check the sub-error before emitting the main error of parser and attach it.
Fix #103869

9 files changed, 39 insertions, 1 deletions

diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs
index 767fb9378be..7ce89b5c359 100644
--- a/compiler/rustc_parse/src/parser/item.rs
+++ b/compiler/rustc_parse/src/parser/item.rs
@@ -1414,7 +1414,10 @@ impl<'a> Parser<'a> {
 
                 Ok((Some(vr), TrailingToken::MaybeComma))
             },
-        )
+        ).map_err(|mut err|{
+            err.help("enum variants can be `Variant`, `Variant = <integer>`, `Variant(Type, ..., TypeN)` or `Variant { fields: Types }`");
+            err
+        })
     }
 
     /// Parses `struct Foo { ... }`.
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 4d8bff28b05..bebb012660a 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -943,6 +943,10 @@ impl<'a> Parser<'a> {
                                 Err(e) => {
                                     // Parsing failed, therefore it must be something more serious
                                     // than just a missing separator.
+                                    for xx in &e.children {
+                                        // propagate the help message from sub error 'e' to main error 'expect_err;
+                                        expect_err.children.push(xx.clone());
+                                    }
                                     expect_err.emit();
 
                                     e.cancel();
diff --git a/src/test/ui/macros/syntax-error-recovery.stderr b/src/test/ui/macros/syntax-error-recovery.stderr
index c153b3b910b..c42ee9b295e 100644
--- a/src/test/ui/macros/syntax-error-recovery.stderr
+++ b/src/test/ui/macros/syntax-error-recovery.stderr
@@ -7,6 +7,7 @@ LL |                 $token $($inner)? = $value,
 LL | values!(STRING(1) as (String) => cfg(test),);
    | -------------------------------------------- in this macro invocation
    |
+   = help: enum variants can be `Variant`, `Variant = <integer>`, `Variant(Type, ..., TypeN)` or `Variant { fields: Types }`
    = note: this error originates in the macro `values` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: macro expansion ignores token `(String)` and any following
diff --git a/src/test/ui/parser/issue-101477-enum.stderr b/src/test/ui/parser/issue-101477-enum.stderr
index bffc881bdc8..1edca391e8f 100644
--- a/src/test/ui/parser/issue-101477-enum.stderr
+++ b/src/test/ui/parser/issue-101477-enum.stderr
@@ -3,6 +3,8 @@ error: unexpected `==`
    |
 LL |     B == 2
    |       ^^ help: try using `=` instead
+   |
+   = help: enum variants can be `Variant`, `Variant = <integer>`, `Variant(Type, ..., TypeN)` or `Variant { fields: Types }`
 
 error: expected item, found `==`
   --> $DIR/issue-101477-enum.rs:6:7
diff --git a/src/test/ui/parser/issue-103869.rs b/src/test/ui/parser/issue-103869.rs
new file mode 100644
index 00000000000..28c442bdd63
--- /dev/null
+++ b/src/test/ui/parser/issue-103869.rs
@@ -0,0 +1,9 @@
+enum VecOrMap{
+    vec: Vec<usize>,
+    //~^ ERROR expected one of `(`, `,`, `=`, `{`, or `}`, found `:`
+    //~| HELP: enum variants can be `Variant`, `Variant = <integer>`, `Variant(Type, ..., TypeN)` or `Variant { fields: Types }`
+    //~| ERROR expected item, found `:`
+    map: HashMap<String,usize>
+}
+
+fn main() {}
diff --git a/src/test/ui/parser/issue-103869.stderr b/src/test/ui/parser/issue-103869.stderr
new file mode 100644
index 00000000000..0b8cd919a9d
--- /dev/null
+++ b/src/test/ui/parser/issue-103869.stderr
@@ -0,0 +1,16 @@
+error: expected one of `(`, `,`, `=`, `{`, or `}`, found `:`
+  --> $DIR/issue-103869.rs:2:8
+   |
+LL |     vec: Vec<usize>,
+   |        ^ expected one of `(`, `,`, `=`, `{`, or `}`
+   |
+   = help: enum variants can be `Variant`, `Variant = <integer>`, `Variant(Type, ..., TypeN)` or `Variant { fields: Types }`
+
+error: expected item, found `:`
+  --> $DIR/issue-103869.rs:2:8
+   |
+LL |     vec: Vec<usize>,
+   |        ^ expected item
+
+error: aborting due to 2 previous errors
+
diff --git a/src/test/ui/parser/macro/issue-37113.stderr b/src/test/ui/parser/macro/issue-37113.stderr
index b1f8674fbdf..da9e743a0b4 100644
--- a/src/test/ui/parser/macro/issue-37113.stderr
+++ b/src/test/ui/parser/macro/issue-37113.stderr
@@ -9,6 +9,7 @@ LL |             $( $t, )*
 LL |     test_macro!(String,);
    |     -------------------- in this macro invocation
    |
+   = help: enum variants can be `Variant`, `Variant = <integer>`, `Variant(Type, ..., TypeN)` or `Variant { fields: Types }`
    = note: this error originates in the macro `test_macro` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
diff --git a/src/test/ui/structs/struct-fn-in-definition.rs b/src/test/ui/structs/struct-fn-in-definition.rs
index 5ae1b727dc7..7f48f55fec9 100644
--- a/src/test/ui/structs/struct-fn-in-definition.rs
+++ b/src/test/ui/structs/struct-fn-in-definition.rs
@@ -28,6 +28,7 @@ enum E {
     //~^ ERROR functions are not allowed in enum definitions
     //~| HELP unlike in C++, Java, and C#, functions are declared in `impl` blocks
     //~| HELP see https://doc.rust-lang.org/book/ch05-03-method-syntax.html for more information
+    //~| HELP enum variants can be `Variant`, `Variant = <integer>`, `Variant(Type, ..., TypeN)` or `Variant { fields: Types }`
 }
 
 fn main() {}
diff --git a/src/test/ui/structs/struct-fn-in-definition.stderr b/src/test/ui/structs/struct-fn-in-definition.stderr
index 472365c6ed7..439c86ec22b 100644
--- a/src/test/ui/structs/struct-fn-in-definition.stderr
+++ b/src/test/ui/structs/struct-fn-in-definition.stderr
@@ -33,6 +33,7 @@ LL |     fn foo() {}
    |
    = help: unlike in C++, Java, and C#, functions are declared in `impl` blocks
    = help: see https://doc.rust-lang.org/book/ch05-03-method-syntax.html for more information
+   = help: enum variants can be `Variant`, `Variant = <integer>`, `Variant(Type, ..., TypeN)` or `Variant { fields: Types }`
 
 error: aborting due to 3 previous errors