root testsuite: added huon's test case from rust-lang#15962.

But I think the one from rust-lang#15750 will be fine.

Makefile

@@ -1,4 +1,5 @@
 FILES= test.bin
+# FILES= test_gensym.bin test.bin
 
 all: $(patsubst %.rs,%.dot,$(FILES))
 
@@ -24,6 +25,8 @@ RUST_LOG=rustc::middle::borrowck,rustc::middle::ty,rustc::middle::typeck,rustc::
 
 test.bin: plugin.dylib
 
+test_gensym.bin: gensym.dylib
+
 %.dot: %.rs Makefile objdir-dbg/x86_64-apple-darwin/stage2/rustc
 	$(RUSTC) -Z flowgraph-print-all --pretty flowgraph=% $< -o $@
 

gensym.rs

@@ -0,0 +1,34 @@
+// gensym.rs
+
+// Taken from Issue #15962
+
+#![feature(plugin_registrar, managed_boxes, quote)]
+#![crate_type = "dylib"]
+
+extern crate syntax;
+extern crate rustc;
+
+use syntax::ast;
+use syntax::codemap::{Span};
+use syntax::ext::base;
+use syntax::ext::base::{ExtCtxt, MacExpr};
+use syntax::ext::build::AstBuilder;
+use syntax::parse::token;
+use rustc::plugin::Registry;
+
+#[plugin_registrar]
+pub fn plugin_registrar(reg: &mut Registry) {
+    reg.register_macro("test_quote", expand_syntax_ext);
+}
+
+pub fn expand_syntax_ext(cx: &mut ExtCtxt, sp: Span, _: &[ast::TokenTree]) -> Box<base::MacResult> {
+    // expand to `{ let foo = true; foo }`, with a gensym'd foo.
+    let ident = token::gensym_ident("foo");
+    let decl = quote_stmt!(&mut *cx, let $ident = true;);
+    let result = cx.expr_block(cx.block(sp, vec![decl], Some(cx.expr_ident(sp, ident))));
+
+    println!("{}", result);
+
+    MacExpr::new(result)
+}
+

test_gensym.rs

@@ -0,0 +1,11 @@
+// test_gensym.rs
+
+// Taken from Issue #15962
+
+#![feature(phase)]
+
+#[phase(plugin)] extern crate gensym;
+
+fn main() {
+    let a = test_quote!();
+}