Fix intersection of two region params in infer, cc #2962

Author: nikomatsakis

src/rustc/middle/typeck/infer.rs

@@ -2371,7 +2371,8 @@ impl of combine for glb {
                 }
               }
 
-              (ty::re_scope(a_id), ty::re_scope(b_id)) {
+              (ty::re_scope(a_id), ty::re_scope(b_id)) |
+              (ty::re_free(a_id, _), ty::re_free(b_id, _)) {
                 // We want to generate a region that is contained by both of
                 // these: so, if one of these scopes is a subscope of the
                 // other, return it.  Otherwise fail.
@@ -2385,7 +2386,6 @@ impl of combine for glb {
 
               // For these types, we cannot define any additional
               // relationship:
-              (ty::re_free(_, _), ty::re_free(_, _)) |
               (ty::re_bound(_), ty::re_bound(_)) |
               (ty::re_bound(_), ty::re_free(_, _)) |
               (ty::re_bound(_), ty::re_scope(_)) |

src/test/compile-fail/regions-infer-call-3.rs

@@ -0,0 +1,14 @@
+fn select(x: &int, y: &int) -> &int { x }
+
+fn with<T>(f: fn(x: &int) -> T) -> T {
+    f(&20)
+}
+
+fn manip(x: &a/int) -> int {
+    let z = do with |y| { select(x, y) };
+    //~^ ERROR reference is not valid outside of its lifetime
+    *z
+}
+
+fn main() {
+}

src/test/run-pass/regions-infer-call-2.rs

@@ -0,0 +1,13 @@
+fn takes_two(x: &int, y: &int) -> int { *x + *y }
+
+fn with<T>(f: fn(x: &int) -> T) -> T {
+    f(&20)
+}
+
+fn has_one(x: &a/int) -> int {
+    do with |y| { takes_two(x, y) }
+}
+
+fn main() {
+    assert has_one(&2) == 22;
+}

src/test/run-pass/regions-infer-call.rs

@@ -0,0 +1,9 @@
+fn takes_two(x: &int, y: &int) -> int { *x + *y }
+
+fn has_two(x: &a/int, y: &b/int) -> int {
+    takes_two(x, y)
+}
+
+fn main() {
+    assert has_two(&20, &2) == 22;
+}