Parse trait bounds containing associated constant constraint

Closes #1138.

src/path.rs

@@ -231,7 +231,38 @@ pub mod parsing {
             }
 
             if input.peek(Ident) && input.peek2(Token![=]) {
-                return Ok(GenericArgument::Binding(input.parse()?));
+                let ident: Ident = input.parse()?;
+                let eq_token: Token![=] = input.parse()?;
+
+                let ty = if input.peek(Lit) {
+                    let begin = input.fork();
+                    input.parse::<Lit>()?;
+                    Type::Verbatim(verbatim::between(begin, input))
+                } else if input.peek(token::Brace) {
+                    let begin = input.fork();
+
+                    #[cfg(feature = "full")]
+                    {
+                        input.parse::<ExprBlock>()?;
+                    }
+
+                    #[cfg(not(feature = "full"))]
+                    {
+                        let content;
+                        braced!(content in input);
+                        content.parse::<Expr>()?;
+                    }
+
+                    Type::Verbatim(verbatim::between(begin, input))
+                } else {
+                    input.parse()?
+                };
+
+                return Ok(GenericArgument::Binding(Binding {
+                    ident,
+                    eq_token,
+                    ty,
+                }));
             }
 
             #[cfg(feature = "full")]

tests/repo/mod.rs

@@ -14,11 +14,6 @@ const REVISION: &str = "e95b10ba4ac4564ed25f7eef143e3182c33b3902";
 
 #[rustfmt::skip]
 static EXCLUDE: &[&str] = &[
-    // TODO: trait bound with associated constant constraint:
-    // where T: Trait<N = 3usize>
-    // https://github.com/dtolnay/syn/issues/1138
-    "src/test/ui/associated-consts/assoc-const.rs",
-
     // TODO: trailing where-clause on impl associated type:
     // impl<T> Trait for Ty<T> { type Assoc<'a> = T where T: 'a; }
     // https://github.com/dtolnay/syn/issues/1071