Merge pull request #30 from dtolnay/var

Preserve macro metavariables not containing a paste
dtolnay · May 24, 2020 · dd8fc9f · dd8fc9f
2 parents 40e90f1 + ab8081b
commit dd8fc9f
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Showing 2 changed files with 53 additions and 18 deletions.
diff --git a/impl/src/lib.rs b/impl/src/lib.rs
@@ -40,31 +40,46 @@ struct PasteInput {
 
 impl Parse for PasteInput {
     fn parse(input: ParseStream) -> Result<Self> {
-        let mut expanded = TokenStream::new();
-        while !input.is_empty() {
-            match input.parse()? {
-                TokenTree::Group(group) => {
-                    let delimiter = group.delimiter();
-                    let content = group.stream();
-                    let span = group.span();
-                    if delimiter == Delimiter::Bracket && is_paste_operation(&content) {
-                        let segments = parse_bracket_as_segments.parse2(content)?;
-                        let pasted = paste_segments(span, &segments)?;
-                        pasted.to_tokens(&mut expanded);
-                    } else if is_none_delimited_single_ident_or_lifetime(delimiter, &content) {
-                        content.to_tokens(&mut expanded);
-                    } else {
-                        let nested = PasteInput::parse.parse2(content)?;
-                        let mut group = Group::new(delimiter, nested.expanded);
+        let mut contains_paste = false;
+        let expanded = parse(input, &mut contains_paste)?;
+        Ok(PasteInput { expanded })
+    }
+}
+
+fn parse(input: ParseStream, contains_paste: &mut bool) -> Result<TokenStream> {
+    let mut expanded = TokenStream::new();
+    while !input.is_empty() {
+        let save = input.fork();
+        match input.parse()? {
+            TokenTree::Group(group) => {
+                let delimiter = group.delimiter();
+                let content = group.stream();
+                let span = group.span();
+                if delimiter == Delimiter::Bracket && is_paste_operation(&content) {
+                    let segments = parse_bracket_as_segments.parse2(content)?;
+                    let pasted = paste_segments(span, &segments)?;
+                    pasted.to_tokens(&mut expanded);
+                    *contains_paste = true;
+                } else if is_none_delimited_single_ident_or_lifetime(delimiter, &content) {
+                    content.to_tokens(&mut expanded);
+                } else {
+                    let mut group_contains_paste = false;
+                    let nested = (|input: ParseStream| parse(input, &mut group_contains_paste))
+                        .parse2(content)?;
+                    if group_contains_paste {
+                        let mut group = Group::new(delimiter, nested);
                         group.set_span(span);
                         group.to_tokens(&mut expanded);
+                        *contains_paste |= group_contains_paste;
+                    } else {
+                        save.parse::<TokenTree>()?.to_tokens(&mut expanded);
                     }
                 }
-                other => other.to_tokens(&mut expanded),
             }
+            other => other.to_tokens(&mut expanded),
         }
-        Ok(PasteInput { expanded })
     }
+    Ok(expanded)
 }
 
 fn is_paste_operation(input: &TokenStream) -> bool {

diff --git a/tests/test.rs b/tests/test.rs
@@ -305,3 +305,23 @@ fn test_env_to_camel() {
         let _ = LIBPaste;
     }
 }
+
+mod test_doc_expr {
+    // https://github.com/dtolnay/paste/issues/29
+
+    macro_rules! doc_expr {
+        ($doc:expr) => {
+            paste::item! {
+                #[doc = $doc]
+                pub struct S;
+            }
+        };
+    }
+
+    doc_expr!(stringify!());
+
+    #[test]
+    fn test_doc_expr() {
+        let _: S;
+    }
+}