this and super don't generate references

This avoids some oddities, such as `this` used in libraries which we previously
had to bind to an artificial built-in.

crates/solidity/inputs/language/bindings/rules.msgb

@@ -304,9 +304,6 @@ inherit .star_extension
   edge heir.ns -> ns_member
   edge ns_member -> @type_name.push_begin
 
-  ; Resolve the "super" keyword reference to the inherited type
-  edge heir.super -> @type_name.push_begin
-
   if (version-matches "< 0.7.0") {
     ; `using` directives are inherited in Solidity < 0.7.0, so connect them to
     ; our own extensions scope
@@ -401,12 +398,6 @@ inherit .star_extension
   edge @contract.lexical_scope -> this
   edge this -> member
 
-  ; ... and resolves to the contract itself
-  node name_push
-  attr (name_push) push_symbol = (source-text @name)
-  edge this -> name_push
-  edge name_push -> @contract.lexical_scope
-
   ;; Modifiers are available as a contract type members through a special '@modifier' guard
   node modifier
   attr (modifier) pop_symbol = "@modifier"
@@ -525,9 +516,6 @@ inherit .star_extension
   attr (super_instance) push_symbol = "@instance"
   edge @contract.super_import -> super_instance
   edge super_instance -> @contract.super_scope
-
-  ; NOTE: The keyword "super" itself resolves to each of its parent contracts.
-  ; See the related rules in the InheritanceSpecifier section above.
 }
 
 @contract [ContractDefinition [InheritanceSpecifier [InheritanceTypes
@@ -743,9 +731,6 @@ inherit .star_extension
 @interface [InterfaceDefinition @specifier [InheritanceSpecifier]] {
   let @specifier.heir = @interface
   attr (@interface.def) parents = @specifier.parent_refs
-
-  ; Define a dummy "super" node required by the rules for InheritanceSpecifier
-  node @interface.super
 }
 
 @interface [InterfaceDefinition [InterfaceMembers
@@ -816,16 +801,6 @@ inherit .star_extension
   edge type -> type_library_type
   edge type_library_type -> @library.lexical_scope
 
-  ; Define `this` inside libraries to resolve to a special built-in placeholder
-  node this
-  attr (this) pop_symbol = "this"
-  node this_built_in
-  attr (this_built_in) push_symbol = "%this"
-
-  edge @library.lexical_scope -> this
-  edge this -> this_built_in
-  edge this_built_in -> @library.parent_scope
-
   ; This is the connection point to resolve attached functions by `using for *`
   node @library.star_extension
   attr (@library.star_extension) push_symbol = "@*"
@@ -2387,9 +2362,7 @@ inherit .star_extension
 }
 
 ;; Identifier expressions
-@expr [Expression @name (
-  variant: [Identifier] | variant: [SuperKeyword] | variant: [ThisKeyword] 
-)] {
+@expr [Expression @name [Identifier]] {
   node ref
   attr (ref) node_reference = @name
   attr (ref) parents = [@expr.enclosing_def]
@@ -2398,6 +2371,14 @@ inherit .star_extension
   edge @expr.output -> ref
 }
 
+@expr [Expression @keyword ([ThisKeyword] | [SuperKeyword])] {
+  ; This is almost equivalent to the above rule, except it doesn't generate a reference
+  node keyword
+  attr (keyword) push_symbol = (source-text @keyword)
+  edge keyword -> @expr.lexical_scope
+  edge @expr.output -> keyword
+}
+
 ;; Member access expressions
 @expr [Expression [MemberAccessExpression
     @operand operand: [Expression]

crates/solidity/inputs/language/src/definition.rs

@@ -7041,7 +7041,6 @@ codegen_language_macros::compile!(Language(
         BuiltInVariable(definition = "$MessageType msg"),
         BuiltInVariable(definition = "uint now", enabled = Till("0.7.0")),
         BuiltInVariable(definition = "$StringType $string"),
-        BuiltInVariable(definition = "$TransactionType tx"),
-        BuiltInVariable(definition = "$ThisType $this")
+        BuiltInVariable(definition = "$TransactionType tx")
     ]
 ));

crates/solidity/testing/snapshots/bindings_output/built_ins/address/generated/0.4.11-failure.txt

@@ -60,10 +60,8 @@ References and definitions:
    │                               │   
    │                               ╰─── ref: built-in
  9 │         uint256 v10 = address(this).balance;
-   │                 ─┬─           ──┬─  ───┬───  
+   │                 ─┬─                 ───┬───  
    │                  ╰─────────────────────────── def: 12
-   │                                 │      │     
-   │                                 ╰──────────── ref: 1
    │                                        │     
    │                                        ╰───── ref: built-in
 ───╯

crates/solidity/testing/snapshots/bindings_output/built_ins/address/generated/0.5.0-success.txt

@@ -60,10 +60,8 @@ References and definitions:
    │                               │   
    │                               ╰─── ref: built-in
  9 │         uint256 v10 = address(this).balance;
-   │                 ─┬─           ──┬─  ───┬───  
+   │                 ─┬─                 ───┬───  
    │                  ╰─────────────────────────── def: 12
-   │                                 │      │     
-   │                                 ╰──────────── ref: 1
    │                                        │     
    │                                        ╰───── ref: built-in
 ───╯

crates/solidity/testing/snapshots/bindings_output/built_ins/function_type/generated/0.4.11-failure.txt

@@ -10,19 +10,15 @@ References and definitions:
     │              ──┬─  
     │                ╰─── def: 2
   3 │         bytes4 v1 = this.test.selector;
-    │                ─┬   ──┬─ ──┬─ ────┬───  
+    │                ─┬        ──┬─ ────┬───  
     │                 ╰─────────────────────── def: 3
-    │                       │    │      │     
-    │                       ╰───────────────── ref: 1
     │                            │      │     
     │                            ╰──────────── ref: 2
     │                                   │     
     │                                   ╰───── unresolved
   4 │         address v2 = this.test.address;
-    │                 ─┬   ──┬─ ──┬─ ───┬───  
+    │                 ─┬        ──┬─ ───┬───  
     │                  ╰────────────────────── def: 4
-    │                        │    │     │     
-    │                        ╰──────────────── ref: 1
     │                             │     │     
     │                             ╰─────────── ref: 2
     │                                   │     

crates/solidity/testing/snapshots/bindings_output/built_ins/function_type/generated/0.4.21-failure.txt

@@ -10,19 +10,15 @@ References and definitions:
     │              ──┬─  
     │                ╰─── def: 2
   3 │         bytes4 v1 = this.test.selector;
-    │                ─┬   ──┬─ ──┬─ ────┬───  
+    │                ─┬        ──┬─ ────┬───  
     │                 ╰─────────────────────── def: 3
-    │                       │    │      │     
-    │                       ╰───────────────── ref: 1
     │                            │      │     
     │                            ╰──────────── ref: 2
     │                                   │     
     │                                   ╰───── ref: built-in
   4 │         address v2 = this.test.address;
-    │                 ─┬   ──┬─ ──┬─ ───┬───  
+    │                 ─┬        ──┬─ ───┬───  
     │                  ╰────────────────────── def: 4
-    │                        │    │     │     
-    │                        ╰──────────────── ref: 1
     │                             │     │     
     │                             ╰─────────── ref: 2
     │                                   │     

crates/solidity/testing/snapshots/bindings_output/built_ins/function_type/generated/0.8.4-success.txt

@@ -10,19 +10,15 @@ References and definitions:
     │              ──┬─  
     │                ╰─── def: 2
   3 │         bytes4 v1 = this.test.selector;
-    │                ─┬   ──┬─ ──┬─ ────┬───  
+    │                ─┬        ──┬─ ────┬───  
     │                 ╰─────────────────────── def: 3
-    │                       │    │      │     
-    │                       ╰───────────────── ref: 1
     │                            │      │     
     │                            ╰──────────── ref: 2
     │                                   │     
     │                                   ╰───── ref: built-in
   4 │         address v2 = this.test.address;
-    │                 ─┬   ──┬─ ──┬─ ───┬───  
+    │                 ─┬        ──┬─ ───┬───  
     │                  ╰────────────────────── def: 4
-    │                        │    │     │     
-    │                        ╰──────────────── ref: 1
     │                             │     │     
     │                             ╰─────────── ref: 2
     │                                   │