From f7a1006a07b396ed239c08d3576597dad103e064 Mon Sep 17 00:00:00 2001
From: Tim Chevalier <chevalier@alum.wellesley.edu>
Date: Tue, 12 Jul 2011 13:42:05 -0700
Subject: [PATCH] Make resolve check for type-variable name-shadowing

Capturing a type argument in the enclosing scope should be an error --
this commit implements that check in resolve, avoiding a potential
assertion failure in trans.

Closes #648.
---
 src/comp/middle/resolve.rs                    | 23 +++++++++++++++----
 src/test/compile-fail/nested-ty-params.rs     |  7 ++----
 .../compile-fail/type-arg-out-of-scope.rs     |  6 +++++
 3 files changed, 26 insertions(+), 10 deletions(-)
 create mode 100644 src/test/compile-fail/type-arg-out-of-scope.rs

diff --git a/src/comp/middle/resolve.rs b/src/comp/middle/resolve.rs
index 6fb22c34d199..080d9270f6ad 100644
--- a/src/comp/middle/resolve.rs
+++ b/src/comp/middle/resolve.rs
@@ -596,6 +596,10 @@ fn def_is_obj_field(&def d) -> bool {
     ret alt (d) { case (ast::def_obj_field(_)) { true } case (_) { false } };
 }
 
+fn def_is_ty_arg(&def d) -> bool {
+    ret alt(d) { case (ast::def_ty_arg(_)) { true } case (_) { false } };
+}
+
 fn lookup_in_scope(&env e, scopes sc, &span sp, &ident name, namespace ns) ->
    option::t[def] {
     fn in_scope(&env e, &span sp, &ident name, &scope s, namespace ns) ->
@@ -666,15 +670,24 @@ fn lookup_in_scope(&env e, scopes sc, &span sp, &ident name, namespace ns) ->
                 if (!option::is_none(fnd)) {
                     auto df = option::get(fnd);
                     if (left_fn && def_is_local(df) ||
-                            left_fn_level2 && def_is_obj_field(df)) {
-                        e.sess.span_fatal(sp,
-                                        "attempted dynamic \
-                                         environment-capture");
+                        left_fn_level2 && def_is_obj_field(df)
+                        || (scope_is_fn(hd) && left_fn
+                            && def_is_ty_arg(df))) {
+                        auto msg = alt (ns) {
+                            case (ns_type) {
+                                "Attempt to use a type \
+                                argument out of scope"
+                            }
+                            case (_) { "attempted dynamic \
+                                       environment-capture" }
+                        };
+                        e.sess.span_fatal(sp, msg);
                     }
                     ret fnd;
                 }
                 if (left_fn) { left_fn_level2 = true; }
-                if (ns == ns_value && !left_fn) { left_fn = scope_is_fn(hd); }
+                if ((ns == ns_value || ns == ns_type) && !left_fn) {
+                    left_fn = scope_is_fn(hd); }
                 sc = *tl;
             }
         }
diff --git a/src/test/compile-fail/nested-ty-params.rs b/src/test/compile-fail/nested-ty-params.rs
index e4fed7f07ec8..bbb246ea1dc4 100644
--- a/src/test/compile-fail/nested-ty-params.rs
+++ b/src/test/compile-fail/nested-ty-params.rs
@@ -1,8 +1,5 @@
-// error-pattern:Unbound type parameter in callee
-/* I'm actually not sure whether this should compile.
-   But having a nice error message seems better than
-   a bounds check failure (which is what was happening
-   before.) */
+// xfail-stage0
+// error-pattern:Attempt to use a type argument out of scope
 fn hd[U](&vec[U] v) -> U {
   fn hd1(&vec[U] w) -> U {
     ret w.(0);
diff --git a/src/test/compile-fail/type-arg-out-of-scope.rs b/src/test/compile-fail/type-arg-out-of-scope.rs
new file mode 100644
index 000000000000..46f365537dfb
--- /dev/null
+++ b/src/test/compile-fail/type-arg-out-of-scope.rs
@@ -0,0 +1,6 @@
+// xfail-stage0
+// error-pattern:Attempt to use a type argument out of scope
+fn foo[T] (&T x) {
+    fn bar(fn (&T) -> T f) { };
+}
+fn main() { foo(1); }