Preserve the whole LangSyntax when parsing doctests

Previously, only the raw string and the `is_ignore` field were
preserved, which made it hard to recover anything else.

Author: jyn514

Diff for: src/librustdoc/html/markdown.rs

@@ -1316,8 +1316,7 @@ crate struct RustCodeBlock {
     /// The range in the markdown that the code within the code block occupies.
     crate code: Range<usize>,
     crate is_fenced: bool,
-    crate syntax: Option<String>,
-    crate is_ignore: bool,
+    crate lang_string: LangString,
 }
 
 /// Returns a range of bytes for each code block in the markdown that is tagged as `rust` or
@@ -1333,7 +1332,7 @@ crate fn rust_code_blocks(md: &str, extra_info: &ExtraInfo<'_>) -> Vec<RustCodeB
 
     while let Some((event, offset)) = p.next() {
         if let Event::Start(Tag::CodeBlock(syntax)) = event {
-            let (syntax, code_start, code_end, range, is_fenced, is_ignore) = match syntax {
+            let (lang_string, code_start, code_end, range, is_fenced) = match syntax {
                 CodeBlockKind::Fenced(syntax) => {
                     let syntax = syntax.as_ref();
                     let lang_string = if syntax.is_empty() {
@@ -1344,8 +1343,6 @@ crate fn rust_code_blocks(md: &str, extra_info: &ExtraInfo<'_>) -> Vec<RustCodeB
                     if !lang_string.rust {
                         continue;
                     }
-                    let is_ignore = lang_string.ignore != Ignore::None;
-                    let syntax = if syntax.is_empty() { None } else { Some(syntax.to_owned()) };
                     let (code_start, mut code_end) = match p.next() {
                         Some((Event::Text(_), offset)) => (offset.start, offset.end),
                         Some((_, sub_offset)) => {
@@ -1354,8 +1351,7 @@ crate fn rust_code_blocks(md: &str, extra_info: &ExtraInfo<'_>) -> Vec<RustCodeB
                                 is_fenced: true,
                                 range: offset,
                                 code,
-                                syntax,
-                                is_ignore,
+                                lang_string,
                             });
                             continue;
                         }
@@ -1365,31 +1361,29 @@ crate fn rust_code_blocks(md: &str, extra_info: &ExtraInfo<'_>) -> Vec<RustCodeB
                                 is_fenced: true,
                                 range: offset,
                                 code,
-                                syntax,
-                                is_ignore,
+                                lang_string,
                             });
                             continue;
                         }
                     };
                     while let Some((Event::Text(_), offset)) = p.next() {
                         code_end = offset.end;
                     }
-                    (syntax, code_start, code_end, offset, true, is_ignore)
+                    (lang_string, code_start, code_end, offset, true)
                 }
                 CodeBlockKind::Indented => {
                     // The ending of the offset goes too far sometime so we reduce it by one in
                     // these cases.
                     if offset.end > offset.start && md.get(offset.end..=offset.end) == Some(&"\n") {
                         (
-                            None,
+                            LangString::default(),
                             offset.start,
                             offset.end,
                             Range { start: offset.start, end: offset.end - 1 },
                             false,
-                            false,
                         )
                     } else {
-                        (None, offset.start, offset.end, offset, false, false)
+                        (LangString::default(), offset.start, offset.end, offset, false)
                     }
                 }
             };
@@ -1398,8 +1392,7 @@ crate fn rust_code_blocks(md: &str, extra_info: &ExtraInfo<'_>) -> Vec<RustCodeB
                 is_fenced,
                 range,
                 code: Range { start: code_start, end: code_end },
-                syntax,
-                is_ignore,
+                lang_string,
             });
         }
     }

Diff for: src/librustdoc/passes/check_code_block_syntax.rs

@@ -61,8 +61,8 @@ impl<'a, 'tcx> SyntaxChecker<'a, 'tcx> {
         };
 
         let hir_id = self.cx.tcx.hir().local_def_id_to_hir_id(local_id);
-        let empty_block = code_block.syntax.is_none() && code_block.is_fenced;
-        let is_ignore = code_block.is_ignore;
+        let empty_block = code_block.lang_string == Default::default() && code_block.is_fenced;
+        let is_ignore = code_block.lang_string.ignore != markdown::Ignore::None;
 
         // The span and whether it is precise or not.
         let (sp, precise_span) = match super::source_span_for_markdown_range(