Merge pull request #1083 from dtolnay/tildeconst

Parse ~const in where-clause
dtolnay · Oct 6, 2021 · 92173e4 · 92173e4
2 parents a7ad301 + f2dbe27
commit 92173e4
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Showing 2 changed files with 44 additions and 8 deletions.
diff --git a/src/generics.rs b/src/generics.rs
@@ -831,6 +831,15 @@ pub mod parsing {
     #[cfg_attr(doc_cfg, doc(cfg(feature = "parsing")))]
     impl Parse for TraitBound {
         fn parse(input: ParseStream) -> Result<Self> {
+            #[cfg(feature = "full")]
+            let tilde_const = if input.peek(Token![~]) && input.peek2(Token![const]) {
+                let tilde_token = input.parse::<Token![~]>()?;
+                let const_token = input.parse::<Token![const]>()?;
+                Some((tilde_token, const_token))
+            } else {
+                None
+            };
+
             let modifier: TraitBoundModifier = input.parse()?;
             let lifetimes: Option<BoundLifetimes> = input.parse()?;
 
@@ -840,6 +849,21 @@ pub mod parsing {
                 path.segments.last_mut().unwrap().arguments = parenthesized;
             }
 
+            #[cfg(feature = "full")]
+            {
+                if let Some((tilde_token, const_token)) = tilde_const {
+                    path.segments.insert(
+                        0,
+                        PathSegment {
+                            ident: Ident::new("const", const_token.span),
+                            arguments: PathArguments::None,
+                        },
+                    );
+                    let (_const, punct) = path.segments.pairs_mut().next().unwrap().into_tuple();
+                    *punct.unwrap() = Token![::](tilde_token.span);
+                }
+            }
+
             Ok(TraitBound {
                 paren_token: None,
                 modifier,
@@ -994,6 +1018,8 @@ mod printing {
     use super::*;
     use crate::attr::FilterAttrs;
     use crate::print::TokensOrDefault;
+    #[cfg(feature = "full")]
+    use crate::punctuated::Pair;
     use proc_macro2::TokenStream;
     #[cfg(feature = "full")]
     use proc_macro2::TokenTree;
@@ -1214,9 +1240,26 @@ mod printing {
     impl ToTokens for TraitBound {
         fn to_tokens(&self, tokens: &mut TokenStream) {
             let to_tokens = |tokens: &mut TokenStream| {
+                #[cfg(feature = "full")]
+                let skip = match self.path.segments.pairs().next() {
+                    Some(Pair::Punctuated(t, p)) if t.ident == "const" => {
+                        Token![~](p.spans[0]).to_tokens(tokens);
+                        t.to_tokens(tokens);
+                        1
+                    }
+                    _ => 0,
+                };
                 self.modifier.to_tokens(tokens);
                 self.lifetimes.to_tokens(tokens);
-                self.path.to_tokens(tokens);
+                #[cfg(feature = "full")]
+                {
+                    self.path.leading_colon.to_tokens(tokens);
+                    tokens.append_all(self.path.segments.pairs().skip(skip));
+                }
+                #[cfg(not(feature = "full"))]
+                {
+                    self.path.to_tokens(tokens);
+                }
             };
             match &self.paren_token {
                 Some(paren) => paren.surround(tokens, to_tokens),

diff --git a/tests/repo/mod.rs b/tests/repo/mod.rs
@@ -18,13 +18,6 @@ static EXCLUDE: &[&str] = &[
     // https://github.com/dtolnay/syn/issues/1051
     "src/test/ui/rfc-2632-const-trait-impl/syntax.rs",
 
-    // TODO: ~const in where-clause
-    // https://github.com/dtolnay/syn/issues/1051
-    "library/alloc/src/borrow.rs",
-    "src/test/ui/rfc-2632-const-trait-impl/inherent-impl-const-bounds.rs",
-    "src/test/ui/rfc-2632-const-trait-impl/trait-where-clause-run.rs",
-    "src/test/ui/rfc-2632-const-trait-impl/trait-where-clause-self-referential.rs",
-
     // Compile-fail expr parameter in const generic position: f::<1 + 2>()
     "src/test/ui/const-generics/early/closing-args-token.rs",
     "src/test/ui/const-generics/early/const-expression-parameter.rs",