[ruby/prism] Implicit rest nodes

Fundamentally, `foo { |bar,| }` is different from `foo { |bar, *| }`
because of arity checks. This PR introduces a new node to handle
that, `ImplicitRestNode`, which goes in the `rest` slot of parameter
nodes instead of `RestParameterNode` instances.

This is also used in a couple of other places, namely:

* pattern matching: `foo in [bar,]`
* multi target: `for foo, in bar do end`
* multi write: `foo, = bar`

Now the only splat nodes with a `NULL` value are when you're
forwarding, as in: `def foo(*) = bar(*)`.

https://github.com/ruby/prism/commit/dba2a3b652

10 files changed, 15 insertions, 41 deletions

diff --git a/test/prism/snapshots/blocks.txt b/test/prism/snapshots/blocks.txt
index 955b087ed3..d3005d1c17 100644
--- a/test/prism/snapshots/blocks.txt
+++ b/test/prism/snapshots/blocks.txt
@@ -762,10 +762,7 @@
             │   │   │   │       └── name: :bar
             │   │   │   ├── optionals: (length: 0)
             │   │   │   ├── rest:
-            │   │   │   │   @ RestParameterNode (location: (54,11)-(54,12))
-            │   │   │   │   ├── name: ∅
-            │   │   │   │   ├── name_loc: ∅
-            │   │   │   │   └── operator_loc: (54,11)-(54,12) = ","
+            │   │   │   │   @ ImplicitRestNode (location: (54,11)-(54,12))
             │   │   │   ├── posts: (length: 0)
             │   │   │   ├── keywords: (length: 0)
             │   │   │   ├── keyword_rest: ∅
diff --git a/test/prism/snapshots/seattlerb/bug236.txt b/test/prism/snapshots/seattlerb/bug236.txt
index 0d9427bfff..a6ee09e21a 100644
--- a/test/prism/snapshots/seattlerb/bug236.txt
+++ b/test/prism/snapshots/seattlerb/bug236.txt
@@ -23,10 +23,7 @@
         │   │   │   │   │       └── name: :a
         │   │   │   │   ├── optionals: (length: 0)
         │   │   │   │   ├── rest:
-        │   │   │   │   │   @ RestParameterNode (location: (1,4)-(1,5))
-        │   │   │   │   │   ├── name: ∅
-        │   │   │   │   │   ├── name_loc: ∅
-        │   │   │   │   │   └── operator_loc: (1,4)-(1,5) = ","
+        │   │   │   │   │   @ ImplicitRestNode (location: (1,4)-(1,5))
         │   │   │   │   ├── posts: (length: 0)
         │   │   │   │   ├── keywords: (length: 0)
         │   │   │   │   ├── keyword_rest: ∅
diff --git a/test/prism/snapshots/seattlerb/masgn_command_call.txt b/test/prism/snapshots/seattlerb/masgn_command_call.txt
index ceb81c0500..7a7b26b9c3 100644
--- a/test/prism/snapshots/seattlerb/masgn_command_call.txt
+++ b/test/prism/snapshots/seattlerb/masgn_command_call.txt
@@ -9,9 +9,7 @@
             │       ├── name: :a
             │       └── depth: 0
             ├── rest:
-            │   @ SplatNode (location: (1,1)-(1,2))
-            │   ├── operator_loc: (1,1)-(1,2) = ","
-            │   └── expression: ∅
+            │   @ ImplicitRestNode (location: (1,1)-(1,2))
             ├── rights: (length: 0)
             ├── lparen_loc: ∅
             ├── rparen_loc: ∅
diff --git a/test/prism/snapshots/seattlerb/parse_pattern_051.txt b/test/prism/snapshots/seattlerb/parse_pattern_051.txt
index fb9c3ee282..6067c109e1 100644
--- a/test/prism/snapshots/seattlerb/parse_pattern_051.txt
+++ b/test/prism/snapshots/seattlerb/parse_pattern_051.txt
@@ -26,7 +26,8 @@
             │       │   │   │   └── flags: decimal
             │       │   │   └── @ IntegerNode (location: (2,7)-(2,8))
             │       │   │       └── flags: decimal
-            │       │   ├── rest: ∅
+            │       │   ├── rest:
+            │       │   │   @ ImplicitRestNode (location: (2,8)-(2,9))
             │       │   ├── posts: (length: 0)
             │       │   ├── opening_loc: (2,3)-(2,4) = "["
             │       │   └── closing_loc: (2,9)-(2,10) = "]"
diff --git a/test/prism/snapshots/unparser/corpus/literal/assignment.txt b/test/prism/snapshots/unparser/corpus/literal/assignment.txt
index ebb343a002..7890d308b2 100644
--- a/test/prism/snapshots/unparser/corpus/literal/assignment.txt
+++ b/test/prism/snapshots/unparser/corpus/literal/assignment.txt
@@ -39,9 +39,7 @@
         │   │   │   │       ├── name: :a
         │   │   │   │       └── depth: 0
         │   │   │   ├── rest:
-        │   │   │   │   @ SplatNode (location: (3,3)-(3,4))
-        │   │   │   │   ├── operator_loc: (3,3)-(3,4) = ","
-        │   │   │   │   └── expression: ∅
+        │   │   │   │   @ ImplicitRestNode (location: (3,3)-(3,4))
         │   │   │   ├── rights: (length: 0)
         │   │   │   ├── lparen_loc: (3,1)-(3,2) = "("
         │   │   │   └── rparen_loc: (3,4)-(3,5) = ")"
@@ -274,9 +272,7 @@
         │   │       ├── name: :a
         │   │       └── depth: 0
         │   ├── rest:
-        │   │   @ SplatNode (location: (13,2)-(13,3))
-        │   │   ├── operator_loc: (13,2)-(13,3) = ","
-        │   │   └── expression: ∅
+        │   │   @ ImplicitRestNode (location: (13,2)-(13,3))
         │   ├── rights: (length: 0)
         │   ├── lparen_loc: (13,0)-(13,1) = "("
         │   ├── rparen_loc: (13,3)-(13,4) = ")"
diff --git a/test/prism/snapshots/unparser/corpus/literal/block.txt b/test/prism/snapshots/unparser/corpus/literal/block.txt
index 76d51d709e..11f92dd01b 100644
--- a/test/prism/snapshots/unparser/corpus/literal/block.txt
+++ b/test/prism/snapshots/unparser/corpus/literal/block.txt
@@ -72,10 +72,7 @@
         │   │   │   │   │       └── name: :a
         │   │   │   │   ├── optionals: (length: 0)
         │   │   │   │   ├── rest:
-        │   │   │   │   │   @ RestParameterNode (location: (5,8)-(5,9))
-        │   │   │   │   │   ├── name: ∅
-        │   │   │   │   │   ├── name_loc: ∅
-        │   │   │   │   │   └── operator_loc: (5,8)-(5,9) = ","
+        │   │   │   │   │   @ ImplicitRestNode (location: (5,8)-(5,9))
         │   │   │   │   ├── posts: (length: 0)
         │   │   │   │   ├── keywords: (length: 0)
         │   │   │   │   ├── keyword_rest: ∅
@@ -108,10 +105,7 @@
         │   │   │   │   │       └── name: :a
         │   │   │   │   ├── optionals: (length: 0)
         │   │   │   │   ├── rest:
-        │   │   │   │   │   @ RestParameterNode (location: (7,8)-(7,9))
-        │   │   │   │   │   ├── name: ∅
-        │   │   │   │   │   ├── name_loc: ∅
-        │   │   │   │   │   └── operator_loc: (7,8)-(7,9) = ","
+        │   │   │   │   │   @ ImplicitRestNode (location: (7,8)-(7,9))
         │   │   │   │   ├── posts: (length: 0)
         │   │   │   │   ├── keywords: (length: 0)
         │   │   │   │   ├── keyword_rest: ∅
diff --git a/test/prism/snapshots/unparser/corpus/literal/pattern.txt b/test/prism/snapshots/unparser/corpus/literal/pattern.txt
index 88a191a334..983ec43050 100644
--- a/test/prism/snapshots/unparser/corpus/literal/pattern.txt
+++ b/test/prism/snapshots/unparser/corpus/literal/pattern.txt
@@ -54,7 +54,8 @@
         │   │   │   │   │   │   └── flags: decimal
         │   │   │   │   │   └── @ IntegerNode (location: (4,7)-(4,8))
         │   │   │   │   │       └── flags: decimal
-        │   │   │   │   ├── rest: ∅
+        │   │   │   │   ├── rest:
+        │   │   │   │   │   @ ImplicitRestNode (location: (4,8)-(4,9))
         │   │   │   │   ├── posts: (length: 0)
         │   │   │   │   ├── opening_loc: (4,3)-(4,4) = "["
         │   │   │   │   └── closing_loc: (4,10)-(4,11) = "]"
diff --git a/test/prism/snapshots/variables.txt b/test/prism/snapshots/variables.txt
index 887b2a1b47..6930d43b25 100644
--- a/test/prism/snapshots/variables.txt
+++ b/test/prism/snapshots/variables.txt
@@ -199,9 +199,7 @@
         │   │       ├── name: :foo
         │   │       └── depth: 0
         │   ├── rest:
-        │   │   @ SplatNode (location: (35,3)-(35,4))
-        │   │   ├── operator_loc: (35,3)-(35,4) = ","
-        │   │   └── expression: ∅
+        │   │   @ ImplicitRestNode (location: (35,3)-(35,4))
         │   ├── rights: (length: 0)
         │   ├── lparen_loc: ∅
         │   ├── rparen_loc: ∅
diff --git a/test/prism/snapshots/whitequark/blockargs.txt b/test/prism/snapshots/whitequark/blockargs.txt
index 150d02bf7a..9e579bee86 100644
--- a/test/prism/snapshots/whitequark/blockargs.txt
+++ b/test/prism/snapshots/whitequark/blockargs.txt
@@ -598,10 +598,7 @@
         │   │   │   │   │       └── name: :b
         │   │   │   │   ├── optionals: (length: 0)
         │   │   │   │   ├── rest:
-        │   │   │   │   │   @ RestParameterNode (location: (37,8)-(37,9))
-        │   │   │   │   │   ├── name: ∅
-        │   │   │   │   │   ├── name_loc: ∅
-        │   │   │   │   │   └── operator_loc: (37,8)-(37,9) = ","
+        │   │   │   │   │   @ ImplicitRestNode (location: (37,8)-(37,9))
         │   │   │   │   ├── posts: (length: 0)
         │   │   │   │   ├── keywords: (length: 0)
         │   │   │   │   ├── keyword_rest: ∅
@@ -859,10 +856,7 @@
         │   │   │   │   │       └── name: :a
         │   │   │   │   ├── optionals: (length: 0)
         │   │   │   │   ├── rest:
-        │   │   │   │   │   @ RestParameterNode (location: (49,5)-(49,6))
-        │   │   │   │   │   ├── name: ∅
-        │   │   │   │   │   ├── name_loc: ∅
-        │   │   │   │   │   └── operator_loc: (49,5)-(49,6) = ","
+        │   │   │   │   │   @ ImplicitRestNode (location: (49,5)-(49,6))
         │   │   │   │   ├── posts: (length: 0)
         │   │   │   │   ├── keywords: (length: 0)
         │   │   │   │   ├── keyword_rest: ∅
diff --git a/test/prism/snapshots/whitequark/masgn_nested.txt b/test/prism/snapshots/whitequark/masgn_nested.txt
index e716762a98..d9513e5813 100644
--- a/test/prism/snapshots/whitequark/masgn_nested.txt
+++ b/test/prism/snapshots/whitequark/masgn_nested.txt
@@ -11,9 +11,7 @@
         │   │       │       ├── name: :b
         │   │       │       └── depth: 0
         │   │       ├── rest:
-        │   │       │   @ SplatNode (location: (1,3)-(1,4))
-        │   │       │   ├── operator_loc: (1,3)-(1,4) = ","
-        │   │       │   └── expression: ∅
+        │   │       │   @ ImplicitRestNode (location: (1,3)-(1,4))
         │   │       ├── rights: (length: 0)
         │   │       ├── lparen_loc: (1,1)-(1,2) = "("
         │   │       └── rparen_loc: (1,5)-(1,6) = ")"