Change error for out of scope type params to be more helpful.

src/librustc/middle/resolve.rs

@@ -3507,8 +3507,9 @@ impl<'a> Resolver<'a> {
                         // its scope.
 
                         self.resolve_error(span,
-                                              "attempt to use a type \
-                                              argument out of scope");
+                                              "can't use type parameters from \
+                                              outer function; try using a local \
+                                              type parameter instead");
                     }
 
                     return None;
@@ -3530,8 +3531,9 @@ impl<'a> Resolver<'a> {
                         // its scope.
 
                         self.resolve_error(span,
-                                              "attempt to use a type \
-                                              argument out of scope");
+                                              "can't use type parameters from \
+                                              outer function; try using a local \
+                                              type parameter instead");
                     }
 
                     return None;

src/librustc/middle/subst.rs

@@ -95,8 +95,9 @@ impl<'a> TypeFolder for SubstFolder<'a> {
                                               root.repr(self.tcx)),
                         None => ~""
                     };
-                    let m = format!("missing type param `{}`{}",
-                                    t.repr(self.tcx), root_msg);
+                    let m = format!("can't use type parameters from outer \
+                                    function{}; try using a local type \
+                                    parameter instead", root_msg);
                     match self.span {
                         Some(span) => self.tcx.sess.span_err(span, m),
                         None => self.tcx.sess.err(m)

src/test/compile-fail/bad-type-env-capture.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 fn foo<T>() {
-    fn bar(b: T) { } //~ ERROR attempt to use a type argument out of scope
+    fn bar(b: T) { } //~ ERROR can't use type parameters from outer
     //~^ ERROR use of undeclared type name
 }
 fn main() { }

src/test/compile-fail/issue-3021-c.rs

@@ -11,8 +11,8 @@
 fn siphash<T>() {
 
     trait t {
-        fn g(&self, x: T) -> T;  //~ ERROR attempt to use a type argument out of scope
-        //~^ ERROR attempt to use a type argument out of scope
+        fn g(&self, x: T) -> T;  //~ ERROR can't use type parameters from outer function; try using
+        //~^ ERROR can't use type parameters from outer function; try using
         //~^^ ERROR use of undeclared type name `T`
         //~^^^ ERROR use of undeclared type name `T`
     }

src/test/compile-fail/issue-3214.rs

@@ -10,7 +10,7 @@
 
 fn foo<T>() {
     struct foo {
-        x: T, //~ ERROR attempt to use a type argument out of scope
+        x: T, //~ ERROR can't use type parameters from outer function;
         //~^ ERROR use of undeclared type name
     }
 

src/test/compile-fail/issue-5997-enum.rs

@@ -10,7 +10,7 @@
 
 fn f<Z>() -> bool {
     enum E { V(Z) }
-    //~^ ERROR missing type param `Z` in the substitution of `Z`
+    //~^ ERROR can't use type parameters from outer function in the
 
     true
 }

src/test/compile-fail/issue-5997-struct.rs

@@ -10,7 +10,7 @@
 
 fn f<T>() -> bool {
     struct S(T); //~ ERROR use of undeclared type name `T`
-    //~^ ERROR attempt to use a type argument out of scope
+    //~^ ERROR can't use type parameters from outer function; try using
 
     true
 }

src/test/compile-fail/nested-ty-params.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern:attempt to use a type argument out of scope
+// error-pattern:can't use type parameters from outer function; try using
 fn hd<U>(v: Vec<U> ) -> U {
     fn hd1(w: [U]) -> U { return w[0]; }
 

src/test/compile-fail/type-arg-out-of-scope.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern:attempt to use a type argument out of scope
+// error-pattern:can't use type parameters from outer function; try using
 fn foo<T>(x: T) {
     fn bar(f: |T| -> T) { }
 }