Fix in handling

in is a unique keyword because it can be the start of a clause or
an infix keyword. We need to be explicitly sure that even though in
_could_ close an expression context (the body of another in clause)
that we are not also parsing an inline in. The exception is the
case of a command call, which can never be the LHS of an expression,
and so we must immediately exit.

Author: kddnewton

snapshots/case_in_in.txt

@@ -0,0 +1,81 @@
+@ ProgramNode (location: (1,0)-(4,3))
+├── flags: ∅
+├── locals: [:event]
+└── statements:
+    @ StatementsNode (location: (1,0)-(4,3))
+    ├── flags: ∅
+    └── body: (length: 1)
+        └── @ CaseMatchNode (location: (1,0)-(4,3))
+            ├── flags: newline
+            ├── predicate:
+            │   @ CallNode (location: (1,5)-(1,9))
+            │   ├── flags: variable_call, ignore_visibility
+            │   ├── receiver: ∅
+            │   ├── call_operator_loc: ∅
+            │   ├── name: :args
+            │   ├── message_loc: (1,5)-(1,9) = "args"
+            │   ├── opening_loc: ∅
+            │   ├── arguments: ∅
+            │   ├── closing_loc: ∅
+            │   ├── equal_loc: ∅
+            │   └── block: ∅
+            ├── conditions: (length: 1)
+            │   └── @ InNode (location: (2,0)-(3,25))
+            │       ├── flags: ∅
+            │       ├── pattern:
+            │       │   @ ArrayPatternNode (location: (2,3)-(2,10))
+            │       │   ├── flags: ∅
+            │       │   ├── constant: ∅
+            │       │   ├── requireds: (length: 1)
+            │       │   │   └── @ LocalVariableTargetNode (location: (2,4)-(2,9))
+            │       │   │       ├── flags: ∅
+            │       │   │       ├── name: :event
+            │       │   │       └── depth: 0
+            │       │   ├── rest: ∅
+            │       │   ├── posts: (length: 0)
+            │       │   ├── opening_loc: (2,3)-(2,4) = "["
+            │       │   └── closing_loc: (2,9)-(2,10) = "]"
+            │       ├── statements:
+            │       │   @ StatementsNode (location: (3,2)-(3,25))
+            │       │   ├── flags: ∅
+            │       │   └── body: (length: 1)
+            │       │       └── @ MatchPredicateNode (location: (3,2)-(3,25))
+            │       │           ├── flags: newline
+            │       │           ├── value:
+            │       │           │   @ CallNode (location: (3,2)-(3,15))
+            │       │           │   ├── flags: ∅
+            │       │           │   ├── receiver:
+            │       │           │   │   @ CallNode (location: (3,2)-(3,9))
+            │       │           │   │   ├── flags: variable_call, ignore_visibility
+            │       │           │   │   ├── receiver: ∅
+            │       │           │   │   ├── call_operator_loc: ∅
+            │       │           │   │   ├── name: :context
+            │       │           │   │   ├── message_loc: (3,2)-(3,9) = "context"
+            │       │           │   │   ├── opening_loc: ∅
+            │       │           │   │   ├── arguments: ∅
+            │       │           │   │   ├── closing_loc: ∅
+            │       │           │   │   ├── equal_loc: ∅
+            │       │           │   │   └── block: ∅
+            │       │           │   ├── call_operator_loc: (3,9)-(3,10) = "."
+            │       │           │   ├── name: :event
+            │       │           │   ├── message_loc: (3,10)-(3,15) = "event"
+            │       │           │   ├── opening_loc: ∅
+            │       │           │   ├── arguments: ∅
+            │       │           │   ├── closing_loc: ∅
+            │       │           │   ├── equal_loc: ∅
+            │       │           │   └── block: ∅
+            │       │           ├── pattern:
+            │       │           │   @ PinnedVariableNode (location: (3,19)-(3,25))
+            │       │           │   ├── flags: ∅
+            │       │           │   ├── variable:
+            │       │           │   │   @ LocalVariableReadNode (location: (3,20)-(3,25))
+            │       │           │   │   ├── flags: ∅
+            │       │           │   │   ├── name: :event
+            │       │           │   │   └── depth: 0
+            │       │           │   └── operator_loc: (3,19)-(3,20) = "^"
+            │       │           └── operator_loc: (3,16)-(3,18) = "in"
+            │       ├── in_loc: (2,0)-(2,2) = "in"
+            │       └── then_loc: ∅
+            ├── else_clause: ∅
+            ├── case_keyword_loc: (1,0)-(1,4) = "case"
+            └── end_keyword_loc: (4,0)-(4,3) = "end"

src/prism.c

@@ -21652,12 +21652,6 @@ parse_expression(pm_parser_t *parser, pm_binding_power_t binding_power, bool acc
      ) {
         node = parse_expression_infix(parser, node, binding_power, current_binding_powers.right, accepts_command_call, (uint16_t) (depth + 1));
 
-        if (context_terminator(parser->current_context->context, &parser->current)) {
-            // If this token terminates the current context, then we need to
-            // stop parsing the expression, as it has become a statement.
-            return node;
-        }
-
         switch (PM_NODE_TYPE(node)) {
             case PM_MULTI_WRITE_NODE:
                 // Multi-write nodes are statements, and cannot be followed by
@@ -21770,6 +21764,17 @@ parse_expression(pm_parser_t *parser, pm_binding_power_t binding_power, bool acc
                     break;
             }
         }
+
+        if (context_terminator(parser->current_context->context, &parser->current)) {
+            pm_binding_powers_t next_binding_powers = pm_binding_powers[parser->current.type];
+            if (
+                !next_binding_powers.binary ||
+                binding_power > next_binding_powers.left ||
+                (PM_NODE_TYPE_P(node, PM_CALL_NODE) && pm_call_node_command_p((pm_call_node_t *) node))
+            ) {
+                return node;
+            }
+        }
     }
 
     return node;

test/prism/fixtures/case_in_in.txt

@@ -0,0 +1,4 @@
+case args
+in [event]
+  context.event in ^event
+end