Use $message_type as the tag

`type` turned out to be controversial.

compiler/rustc_errors/src/json.rs

@@ -158,7 +158,7 @@ impl JsonEmitter {
 }
 
 #[derive(Serialize)]
-#[serde(tag = "type", rename_all = "snake_case")]
+#[serde(tag = "$message_type", rename_all = "snake_case")]
 enum EmitTyped<'a> {
     Diagnostic(Diagnostic),
     Artifact(ArtifactNotification<'a>),

tests/ui/diagnostic-width/flag-json.stderr

@@ -1,4 +1,4 @@
-{"type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
+{"$message_type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
 
 Erroneous code examples:
 
@@ -33,8 +33,8 @@ LL | ..._: () = 42;
    |       expected due to this
 
 "}
-{"type":"diagnostic","message":"aborting due to previous error","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to previous error
+{"$message_type":"diagnostic","message":"aborting due to previous error","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to previous error
 
 "}
-{"type":"diagnostic","message":"For more information about this error, try `rustc --explain E0308`.","code":null,"level":"failure-note","spans":[],"children":[],"rendered":"For more information about this error, try `rustc --explain E0308`.
+{"$message_type":"diagnostic","message":"For more information about this error, try `rustc --explain E0308`.","code":null,"level":"failure-note","spans":[],"children":[],"rendered":"For more information about this error, try `rustc --explain E0308`.
 "}

tests/ui/json/json-bom-plus-crlf-multifile.stderr

@@ -1,4 +1,4 @@
-{"type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
+{"$message_type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
 
 Erroneous code examples:
 
@@ -26,7 +26,7 @@ most common being when calling a function and passing an argument which has a
 different type than the matching type in the function declaration.
 "},"level":"error","spans":[{"file_name":"$DIR/json-bom-plus-crlf-multifile-aux.rs","byte_start":621,"byte_end":622,"line_start":17,"line_end":17,"column_start":22,"column_end":23,"is_primary":true,"text":[{"text":"    let s : String = 1;  // Error in the middle of line.","highlight_start":22,"highlight_end":23}],"label":"expected `String`, found integer","suggested_replacement":null,"suggestion_applicability":null,"expansion":null},{"file_name":"$DIR/json-bom-plus-crlf-multifile-aux.rs","byte_start":612,"byte_end":618,"line_start":17,"line_end":17,"column_start":13,"column_end":19,"is_primary":false,"text":[{"text":"    let s : String = 1;  // Error in the middle of line.","highlight_start":13,"highlight_end":19}],"label":"expected due to this","suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"try using a conversion method","code":null,"level":"help","spans":[{"file_name":"$DIR/json-bom-plus-crlf-multifile-aux.rs","byte_start":622,"byte_end":622,"line_start":17,"line_end":17,"column_start":23,"column_end":23,"is_primary":true,"text":[{"text":"    let s : String = 1;  // Error in the middle of line.","highlight_start":23,"highlight_end":23}],"label":null,"suggested_replacement":".to_string()","suggestion_applicability":"MaybeIncorrect","expansion":null}],"children":[],"rendered":null}],"rendered":"$DIR/json-bom-plus-crlf-multifile-aux.rs:17:22: error[E0308]: mismatched types
 "}
-{"type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
+{"$message_type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
 
 Erroneous code examples:
 
@@ -54,7 +54,7 @@ most common being when calling a function and passing an argument which has a
 different type than the matching type in the function declaration.
 "},"level":"error","spans":[{"file_name":"$DIR/json-bom-plus-crlf-multifile-aux.rs","byte_start":681,"byte_end":682,"line_start":19,"line_end":19,"column_start":22,"column_end":23,"is_primary":true,"text":[{"text":"    let s : String = 1","highlight_start":22,"highlight_end":23}],"label":"expected `String`, found integer","suggested_replacement":null,"suggestion_applicability":null,"expansion":null},{"file_name":"$DIR/json-bom-plus-crlf-multifile-aux.rs","byte_start":672,"byte_end":678,"line_start":19,"line_end":19,"column_start":13,"column_end":19,"is_primary":false,"text":[{"text":"    let s : String = 1","highlight_start":13,"highlight_end":19}],"label":"expected due to this","suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"try using a conversion method","code":null,"level":"help","spans":[{"file_name":"$DIR/json-bom-plus-crlf-multifile-aux.rs","byte_start":682,"byte_end":682,"line_start":19,"line_end":19,"column_start":23,"column_end":23,"is_primary":true,"text":[{"text":"    let s : String = 1","highlight_start":23,"highlight_end":23}],"label":null,"suggested_replacement":".to_string()","suggestion_applicability":"MaybeIncorrect","expansion":null}],"children":[],"rendered":null}],"rendered":"$DIR/json-bom-plus-crlf-multifile-aux.rs:19:22: error[E0308]: mismatched types
 "}
-{"type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
+{"$message_type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
 
 Erroneous code examples:
 
@@ -82,7 +82,7 @@ most common being when calling a function and passing an argument which has a
 different type than the matching type in the function declaration.
 "},"level":"error","spans":[{"file_name":"$DIR/json-bom-plus-crlf-multifile-aux.rs","byte_start":745,"byte_end":746,"line_start":23,"line_end":23,"column_start":1,"column_end":2,"is_primary":true,"text":[{"text":"1;  // Error after the newline.","highlight_start":1,"highlight_end":2}],"label":"expected `String`, found integer","suggested_replacement":null,"suggestion_applicability":null,"expansion":null},{"file_name":"$DIR/json-bom-plus-crlf-multifile-aux.rs","byte_start":735,"byte_end":741,"line_start":22,"line_end":22,"column_start":13,"column_end":19,"is_primary":false,"text":[{"text":"    let s : String =","highlight_start":13,"highlight_end":19}],"label":"expected due to this","suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"try using a conversion method","code":null,"level":"help","spans":[{"file_name":"$DIR/json-bom-plus-crlf-multifile-aux.rs","byte_start":746,"byte_end":746,"line_start":23,"line_end":23,"column_start":2,"column_end":2,"is_primary":true,"text":[{"text":"1;  // Error after the newline.","highlight_start":2,"highlight_end":2}],"label":null,"suggested_replacement":".to_string()","suggestion_applicability":"MaybeIncorrect","expansion":null}],"children":[],"rendered":null}],"rendered":"$DIR/json-bom-plus-crlf-multifile-aux.rs:23:1: error[E0308]: mismatched types
 "}
-{"type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
+{"$message_type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
 
 Erroneous code examples:
 
@@ -110,5 +110,5 @@ most common being when calling a function and passing an argument which has a
 different type than the matching type in the function declaration.
 "},"level":"error","spans":[{"file_name":"$DIR/json-bom-plus-crlf-multifile-aux.rs","byte_start":801,"byte_end":809,"line_start":25,"line_end":26,"column_start":22,"column_end":6,"is_primary":true,"text":[{"text":"    let s : String = (","highlight_start":22,"highlight_end":23},{"text":"    );  // Error spanning the newline.","highlight_start":1,"highlight_end":6}],"label":"expected `String`, found `()`","suggested_replacement":null,"suggestion_applicability":null,"expansion":null},{"file_name":"$DIR/json-bom-plus-crlf-multifile-aux.rs","byte_start":792,"byte_end":798,"line_start":25,"line_end":25,"column_start":13,"column_end":19,"is_primary":false,"text":[{"text":"    let s : String = (","highlight_start":13,"highlight_end":19}],"label":"expected due to this","suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[],"rendered":"$DIR/json-bom-plus-crlf-multifile-aux.rs:25:22: error[E0308]: mismatched types
 "}
-{"type":"diagnostic","message":"aborting due to 4 previous errors","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to 4 previous errors
+{"$message_type":"diagnostic","message":"aborting due to 4 previous errors","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to 4 previous errors
 "}

tests/ui/json/json-bom-plus-crlf.stderr

@@ -1,4 +1,4 @@
-{"type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
+{"$message_type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
 
 Erroneous code examples:
 
@@ -26,7 +26,7 @@ most common being when calling a function and passing an argument which has a
 different type than the matching type in the function declaration.
 "},"level":"error","spans":[{"file_name":"$DIR/json-bom-plus-crlf.rs","byte_start":606,"byte_end":607,"line_start":16,"line_end":16,"column_start":22,"column_end":23,"is_primary":true,"text":[{"text":"    let s : String = 1;  // Error in the middle of line.","highlight_start":22,"highlight_end":23}],"label":"expected `String`, found integer","suggested_replacement":null,"suggestion_applicability":null,"expansion":null},{"file_name":"$DIR/json-bom-plus-crlf.rs","byte_start":597,"byte_end":603,"line_start":16,"line_end":16,"column_start":13,"column_end":19,"is_primary":false,"text":[{"text":"    let s : String = 1;  // Error in the middle of line.","highlight_start":13,"highlight_end":19}],"label":"expected due to this","suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"try using a conversion method","code":null,"level":"help","spans":[{"file_name":"$DIR/json-bom-plus-crlf.rs","byte_start":607,"byte_end":607,"line_start":16,"line_end":16,"column_start":23,"column_end":23,"is_primary":true,"text":[{"text":"    let s : String = 1;  // Error in the middle of line.","highlight_start":23,"highlight_end":23}],"label":null,"suggested_replacement":".to_string()","suggestion_applicability":"MaybeIncorrect","expansion":null}],"children":[],"rendered":null}],"rendered":"$DIR/json-bom-plus-crlf.rs:16:22: error[E0308]: mismatched types
 "}
-{"type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
+{"$message_type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
 
 Erroneous code examples:
 
@@ -54,7 +54,7 @@ most common being when calling a function and passing an argument which has a
 different type than the matching type in the function declaration.
 "},"level":"error","spans":[{"file_name":"$DIR/json-bom-plus-crlf.rs","byte_start":666,"byte_end":667,"line_start":18,"line_end":18,"column_start":22,"column_end":23,"is_primary":true,"text":[{"text":"    let s : String = 1","highlight_start":22,"highlight_end":23}],"label":"expected `String`, found integer","suggested_replacement":null,"suggestion_applicability":null,"expansion":null},{"file_name":"$DIR/json-bom-plus-crlf.rs","byte_start":657,"byte_end":663,"line_start":18,"line_end":18,"column_start":13,"column_end":19,"is_primary":false,"text":[{"text":"    let s : String = 1","highlight_start":13,"highlight_end":19}],"label":"expected due to this","suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"try using a conversion method","code":null,"level":"help","spans":[{"file_name":"$DIR/json-bom-plus-crlf.rs","byte_start":667,"byte_end":667,"line_start":18,"line_end":18,"column_start":23,"column_end":23,"is_primary":true,"text":[{"text":"    let s : String = 1","highlight_start":23,"highlight_end":23}],"label":null,"suggested_replacement":".to_string()","suggestion_applicability":"MaybeIncorrect","expansion":null}],"children":[],"rendered":null}],"rendered":"$DIR/json-bom-plus-crlf.rs:18:22: error[E0308]: mismatched types
 "}
-{"type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
+{"$message_type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
 
 Erroneous code examples:
 
@@ -82,7 +82,7 @@ most common being when calling a function and passing an argument which has a
 different type than the matching type in the function declaration.
 "},"level":"error","spans":[{"file_name":"$DIR/json-bom-plus-crlf.rs","byte_start":730,"byte_end":731,"line_start":22,"line_end":22,"column_start":1,"column_end":2,"is_primary":true,"text":[{"text":"1;  // Error after the newline.","highlight_start":1,"highlight_end":2}],"label":"expected `String`, found integer","suggested_replacement":null,"suggestion_applicability":null,"expansion":null},{"file_name":"$DIR/json-bom-plus-crlf.rs","byte_start":720,"byte_end":726,"line_start":21,"line_end":21,"column_start":13,"column_end":19,"is_primary":false,"text":[{"text":"    let s : String =","highlight_start":13,"highlight_end":19}],"label":"expected due to this","suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[{"message":"try using a conversion method","code":null,"level":"help","spans":[{"file_name":"$DIR/json-bom-plus-crlf.rs","byte_start":731,"byte_end":731,"line_start":22,"line_end":22,"column_start":2,"column_end":2,"is_primary":true,"text":[{"text":"1;  // Error after the newline.","highlight_start":2,"highlight_end":2}],"label":null,"suggested_replacement":".to_string()","suggestion_applicability":"MaybeIncorrect","expansion":null}],"children":[],"rendered":null}],"rendered":"$DIR/json-bom-plus-crlf.rs:22:1: error[E0308]: mismatched types
 "}
-{"type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
+{"$message_type":"diagnostic","message":"mismatched types","code":{"code":"E0308","explanation":"Expected type did not match the received type.
 
 Erroneous code examples:
 
@@ -110,5 +110,5 @@ most common being when calling a function and passing an argument which has a
 different type than the matching type in the function declaration.
 "},"level":"error","spans":[{"file_name":"$DIR/json-bom-plus-crlf.rs","byte_start":786,"byte_end":794,"line_start":24,"line_end":25,"column_start":22,"column_end":6,"is_primary":true,"text":[{"text":"    let s : String = (","highlight_start":22,"highlight_end":23},{"text":"    );  // Error spanning the newline.","highlight_start":1,"highlight_end":6}],"label":"expected `String`, found `()`","suggested_replacement":null,"suggestion_applicability":null,"expansion":null},{"file_name":"$DIR/json-bom-plus-crlf.rs","byte_start":777,"byte_end":783,"line_start":24,"line_end":24,"column_start":13,"column_end":19,"is_primary":false,"text":[{"text":"    let s : String = (","highlight_start":13,"highlight_end":19}],"label":"expected due to this","suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[],"rendered":"$DIR/json-bom-plus-crlf.rs:24:22: error[E0308]: mismatched types
 "}
-{"type":"diagnostic","message":"aborting due to 4 previous errors","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to 4 previous errors
+{"$message_type":"diagnostic","message":"aborting due to 4 previous errors","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to 4 previous errors
 "}

tests/ui/json/json-multiple.stderr

@@ -1 +1 @@
-{"type":"artifact","artifact":"$TEST_BUILD_DIR/json/json-multiple/libjson_multiple.rlib","emit":"link"}
+{"$message_type":"artifact","artifact":"$TEST_BUILD_DIR/json/json-multiple/libjson_multiple.rlib","emit":"link"}

tests/ui/json/json-options.stderr

@@ -1 +1 @@
-{"type":"artifact","artifact":"$TEST_BUILD_DIR/json/json-options/libjson_options.rlib","emit":"link"}
+{"$message_type":"artifact","artifact":"$TEST_BUILD_DIR/json/json-options/libjson_options.rlib","emit":"link"}

tests/ui/json/json-short.stderr

@@ -1,4 +1,4 @@
-{"type":"diagnostic","message":"`main` function not found in crate `json_short`","code":{"code":"E0601","explanation":"No `main` function was found in a binary crate.
+{"$message_type":"diagnostic","message":"`main` function not found in crate `json_short`","code":{"code":"E0601","explanation":"No `main` function was found in a binary crate.
 
 To fix this error, add a `main` function:
 
@@ -15,5 +15,5 @@ If you don't know the basics of Rust, you can look at the
 [rust-book]: https://doc.rust-lang.org/book/
 "},"level":"error","spans":[{"file_name":"$DIR/json-short.rs","byte_start":62,"byte_end":62,"line_start":1,"line_end":1,"column_start":63,"column_end":63,"is_primary":true,"text":[{"text":"// compile-flags: --json=diagnostic-short --error-format=json","highlight_start":63,"highlight_end":63}],"label":"consider adding a `main` function to `$DIR/json-short.rs`","suggested_replacement":null,"suggestion_applicability":null,"expansion":null}],"children":[],"rendered":"$DIR/json-short.rs:1:63: error[E0601]: `main` function not found in crate `json_short`
 "}
-{"type":"diagnostic","message":"aborting due to previous error","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to previous error
+{"$message_type":"diagnostic","message":"aborting due to previous error","code":null,"level":"error","spans":[],"children":[],"rendered":"error: aborting due to previous error
 "}