Add comments to hygiene tests

src/test/ui/hygiene/cross-crate-define-and-use.rs

@@ -1,3 +1,8 @@
+// Check that a marco from another crate can define an item in one expansion
+// and use it from another, without it being visible to everyone.
+// This requires that the definition of `my_struct` preserves the hygiene
+// information for the tokens in its definition.
+
 // check-pass
 // aux-build:use_by_macro.rs
 

src/test/ui/hygiene/cross-crate-fields.rs

@@ -1,3 +1,6 @@
+// Test that fields on a struct defined in another crate are resolved correctly
+// their names differ only in `SyntaxContext`.
+
 // run-pass
 // aux-build:fields.rs
 

src/test/ui/hygiene/cross-crate-glob-hygiene.rs

@@ -1,3 +1,8 @@
+// Check that globs cannot import hygienic identifiers from a macro expansion
+// in another crate. `my_struct` is a `macro_rules` macro, so the struct it
+// defines is only not imported because `my_struct` is defined by a macros 2.0
+// macro.
+
 // aux-build:use_by_macro.rs
 
 extern crate use_by_macro;

src/test/ui/hygiene/cross-crate-glob-hygiene.stderr

@@ -1,5 +1,5 @@
 error[E0422]: cannot find struct, variant or union type `MyStruct` in this scope
-  --> $DIR/cross-crate-glob-hygiene.rs:16:13
+  --> $DIR/cross-crate-glob-hygiene.rs:21:13
    |
 LL |     let x = my_struct!(create);
    |             ^^^^^^^^^^^^^^^^^^ not found in this scope

src/test/ui/hygiene/cross-crate-methods.rs

@@ -1,3 +1,7 @@
+// Test that methods defined in another crate are resolved correctly their
+// names differ only in `SyntaxContext`. This also checks that any name
+// resolution done when monomorphizing is correct.
+
 // run-pass
 // aux-build:methods.rs
 

src/test/ui/hygiene/cross-crate-name-collision.rs

@@ -1,3 +1,7 @@
+// Check that two items defined in another crate that have identifiers that
+// only differ by `SyntaxContext` do not cause name collisions when imported
+// in another crate.
+
 // check-pass
 // aux-build:needs_hygiene.rs
 

src/test/ui/hygiene/cross-crate-name-hiding-2.rs

@@ -1,3 +1,6 @@
+// Check that an identifier from a 2.0 macro in another crate cannot be
+// resolved with an identifier that's not from a macro expansion.
+
 // aux-build:use_by_macro.rs
 
 extern crate use_by_macro;

src/test/ui/hygiene/cross-crate-name-hiding-2.stderr

@@ -1,5 +1,5 @@
 error[E0422]: cannot find struct, variant or union type `MyStruct` in this scope
-  --> $DIR/cross-crate-name-hiding-2.rs:10:13
+  --> $DIR/cross-crate-name-hiding-2.rs:13:13
    |
 LL |     let x = MyStruct {};
    |             ^^^^^^^^ not found in this scope

src/test/ui/hygiene/cross-crate-name-hiding.rs

@@ -1,3 +1,6 @@
+// Check that an item defined by a 2.0 macro in another crate cannot be used in
+// another crate.
+
 // aux-build:pub_hygiene.rs
 
 extern crate pub_hygiene;

src/test/ui/hygiene/cross-crate-name-hiding.stderr

@@ -1,5 +1,5 @@
 error[E0422]: cannot find struct, variant or union type `MyStruct` in this scope
-  --> $DIR/cross-crate-name-hiding.rs:8:13
+  --> $DIR/cross-crate-name-hiding.rs:11:13
    |
 LL |     let x = MyStruct {};
    |             ^^^^^^^^ not found in this scope

src/test/ui/hygiene/cross-crate-redefine.rs

@@ -1,3 +1,6 @@
+// Check that items with identical `SyntaxContext` conflict even when that
+// context involves a mark from another crate.
+
 // aux-build:use_by_macro.rs
 
 extern crate use_by_macro;

src/test/ui/hygiene/cross-crate-redefine.stderr

@@ -1,5 +1,5 @@
 error[E0428]: the name `MyStruct` is defined multiple times
-  --> $DIR/cross-crate-redefine.rs:7:1
+  --> $DIR/cross-crate-redefine.rs:10:1
    |
 LL | my_struct!(define);
    | ^^^^^^^^^^^^^^^^^^ `MyStruct` redefined here

src/test/ui/hygiene/cross-crate-variants.rs

@@ -1,3 +1,6 @@
+// Test that variants of an enum defined in another crate are resolved
+// correctly when their names differ only in `SyntaxContext`.
+
 // run-pass
 // aux-build:variants.rs