Merge #4246

4246: Validate uses of self and super r=matklad a=djrenren

This change follows on the validation of the `crate` keyword in paths. It verifies the following things:

`super`:
 - May only be preceded by other `super` segments
 - If in a `UseItem` then all semantically preceding paths also consist only of `super`

`self`
 - May only be the start of a path


Just a note, a couple times while working on this I found myself really wanting a Visitor of some sort so that I could traverse descendants while skipping sub-trees that are unimportant. Iterators don't really work for this, so as you can see I reached for recursion. Considering paths are generally small a fancy debounced visitor probably isn't important but figured I'd say something in case we had something like this lying around and I wasn't using it.

Co-authored-by: John Renner <[email protected]>

6 files changed, 104 insertions, 26 deletions

diff --git a/crates/ra_syntax/test_data/parser/err/0041_illegal_super_keyword_location.rast b/crates/ra_syntax/test_data/parser/err/0041_illegal_super_keyword_location.rast
new file mode 100644
index 000000000..d0360c467
--- /dev/null
+++ b/crates/ra_syntax/test_data/parser/err/0041_illegal_super_keyword_location.rast
@@ -0,0 +1,70 @@
+[email protected]
+  [email protected]
+    [email protected] "use"
+    [email protected] " "
+    [email protected]
+      [email protected]
+        [email protected]
+          [email protected] "::"
+          [email protected] "super"
+    [email protected] ";"
+  [email protected] "\n"
+  [email protected]
+    [email protected] "use"
+    [email protected] " "
+    [email protected]
+      [email protected]
+        [email protected]
+          [email protected]
+            [email protected]
+              [email protected] "a"
+        [email protected] "::"
+        [email protected]
+          [email protected] "super"
+    [email protected] ";"
+  [email protected] "\n"
+  [email protected]
+    [email protected] "use"
+    [email protected] " "
+    [email protected]
+      [email protected]
+        [email protected]
+          [email protected]
+            [email protected]
+              [email protected] "super"
+          [email protected] "::"
+          [email protected]
+            [email protected]
+              [email protected] "a"
+        [email protected] "::"
+        [email protected]
+          [email protected] "super"
+    [email protected] ";"
+  [email protected] "\n"
+  [email protected]
+    [email protected] "use"
+    [email protected] " "
+    [email protected]
+      [email protected]
+        [email protected]
+          [email protected]
+            [email protected] "a"
+      [email protected] "::"
+      [email protected]
+        [email protected] "{"
+        [email protected]
+          [email protected]
+            [email protected]
+              [email protected]
+                [email protected] "super"
+            [email protected] "::"
+            [email protected]
+              [email protected]
+                [email protected] "b"
+        [email protected] "}"
+    [email protected] ";"
+  [email protected] "\n"
+error 6..11: The `super` keyword may only be preceded by other `super`s
+error 20..25: The `super` keyword may only be preceded by other `super`s
+error 41..46: The `super` keyword may only be preceded by other `super`s
+error 56..61: The `super` keyword may only be preceded by other `super`s
diff --git a/crates/ra_syntax/test_data/parser/err/0041_illegal_super_keyword_location.rs b/crates/ra_syntax/test_data/parser/err/0041_illegal_super_keyword_location.rs
new file mode 100644
index 000000000..bd4d58042
--- /dev/null
+++ b/crates/ra_syntax/test_data/parser/err/0041_illegal_super_keyword_location.rs
@@ -0,0 +1,4 @@
+use ::super;
+use a::super;
+use super::a::super;
+use a::{super::b};
diff --git a/crates/ra_syntax/test_data/parser/err/0042_illegal_self_keyword_location.rast b/crates/ra_syntax/test_data/parser/err/0042_illegal_self_keyword_location.rast
new file mode 100644
index 000000000..4f382b06c
--- /dev/null
+++ b/crates/ra_syntax/test_data/parser/err/0042_illegal_self_keyword_location.rast
@@ -0,0 +1,27 @@
+[email protected]
+  [email protected]
+    [email protected] "use"
+    [email protected] " "
+    [email protected]
+      [email protected]
+        [email protected]
+          [email protected] "::"
+          [email protected] "self"
+    [email protected] ";"
+  [email protected] "\n"
+  [email protected]
+    [email protected] "use"
+    [email protected] " "
+    [email protected]
+      [email protected]
+        [email protected]
+          [email protected]
+            [email protected]
+              [email protected] "a"
+        [email protected] "::"
+        [email protected]
+          [email protected] "self"
+    [email protected] ";"
+  [email protected] "\n"
+error 6..10: The `self` keyword is only allowed as the first segment of a path
+error 19..23: The `self` keyword is only allowed as the first segment of a path
diff --git a/crates/ra_syntax/test_data/parser/err/0042_illegal_self_keyword_location.rs b/crates/ra_syntax/test_data/parser/err/0042_illegal_self_keyword_location.rs
new file mode 100644
index 000000000..b9e1d7d8b
--- /dev/null
+++ b/crates/ra_syntax/test_data/parser/err/0042_illegal_self_keyword_location.rs
@@ -0,0 +1,2 @@
+use ::self;
+use a::self;
diff --git a/crates/ra_syntax/test_data/parser/ok/0013_use_path_self_super.rast b/crates/ra_syntax/test_data/parser/ok/0013_use_path_self_super.rast
index a5a90df7b..05d9c05ad 100644
--- a/crates/ra_syntax/test_data/parser/ok/0013_use_path_self_super.rast
+++ b/crates/ra_syntax/test_data/parser/ok/0013_use_path_self_super.rast
@@ -1,4 +1,4 @@
-SOURCE_FILE@0..65
+SOURCE_FILE@0..38
   [email protected]
     [email protected] "use"
     [email protected] " "
@@ -31,27 +31,3 @@ [email protected]
             [email protected] "bar"
     [email protected] ";"
   [email protected] "\n"
-  [email protected]
-    [email protected] "use"
-    [email protected] " "
-    [email protected]
-      [email protected]
-        [email protected]
-          [email protected]
-            [email protected]
-              [email protected]
-                [email protected] "::"
-                [email protected] "self"
-            [email protected] "::"
-            [email protected]
-              [email protected]
-                [email protected] "a"
-          [email protected] "::"
-          [email protected]
-            [email protected] "super"
-        [email protected] "::"
-        [email protected]
-          [email protected]
-            [email protected] "bar"
-    [email protected] ";"
-  [email protected] "\n"
diff --git a/crates/ra_syntax/test_data/parser/ok/0013_use_path_self_super.rs b/crates/ra_syntax/test_data/parser/ok/0013_use_path_self_super.rs
index faf6a42c7..9d9eb9917 100644
--- a/crates/ra_syntax/test_data/parser/ok/0013_use_path_self_super.rs
+++ b/crates/ra_syntax/test_data/parser/ok/0013_use_path_self_super.rs
@@ -1,3 +1,2 @@
 use self::foo;
 use super::super::bar;
-use ::self::a::super::bar;