Contextual only tests

Author: CrooseGit

compiler/rustc_span/src/symbol.rs

@@ -61,7 +61,6 @@ symbols! {
         Mod:                "mod",
         Move:               "move",
         Mut:                "mut",
-        Only:               "only",
         Pub:                "pub",
         Ref:                "ref",
         Return:             "return",
@@ -130,6 +129,7 @@ symbols! {
         ContractRequires:   "contract_requires",
         Default:            "default",
         MacroRules:         "macro_rules",
+        Only:               "only",
         Raw:                "raw",
         Reuse:              "reuse",
         Safe:               "safe",

tests/ui/trait-bounds/only-bound.rs

@@ -50,4 +50,37 @@ trait InheritedOnly: OnlyPointeeSized {
     }
 }
 
+
+
+fn only(){
+    let only = 0u32;
+}
+
+mod a{
+    #[allow(non_camel_case_types)]
+    struct only {}
+}
+
+mod b {
+    use std::marker::{MetaSized, PointeeSized};
+
+    #[allow(non_camel_case_types)]
+    trait only: only PointeeSized {
+        fn foo(&self) {
+            size_of_val(self);
+            //~^ ERROR the size for values of type `Self` cannot be known
+        }
+    }
+}
+
+mod only{
+   pub trait Alpha {}
+}
+
+// In the below context, rust will attempt to look for `Alpha` in the crate root, not in a module
+// `only`
+//fn alpha<T: only::Alpha>(){
+//}
+
+
 fn main() {}

tests/ui/trait-bounds/only-bound.stderr

@@ -77,6 +77,24 @@ LL |         size_of_val(&self);
 LL |         size_of_val(&mut self);
    |                     ++++
 
-error: aborting due to 7 previous errors
+error[E0277]: the size for values of type `Self` cannot be known
+  --> $DIR/only-bound.rs:70:25
+   |
+LL |             size_of_val(self);
+   |             ----------- ^^^^ the trait `MetaSized` is not implemented for `Self`
+   |             |
+   |             required by a bound introduced by this call
+   |
+   = note: the trait bound `Self: MetaSized` is not satisfied
+note: required by a bound in `std::mem::size_of_val`
+  --> $SRC_DIR/core/src/mem/mod.rs:LL:COL
+help: consider borrowing here
+   |
+LL |             size_of_val(&self);
+   |                         +
+LL |             size_of_val(&mut self);
+   |                         ++++
+
+error: aborting due to 8 previous errors
 
 For more information about this error, try `rustc --explain E0277`.