Fix jashkenas#5013: return statement as an expression (jashkenas#5014)

* fix jashkenas#5013

* disallow statement in the expression

Author: zdenko

lib/coffeescript/nodes.js

@@ -863,11 +863,6 @@ exports.Value = class Value extends Base
   constructor: (base, props, tag, isDefaultValue = no) ->
     super()
     return base if not props and base instanceof Value
-    # When `Parens` block includes a `StatementLiteral` (e.g. `(b; break) for a in arr`),
-    # it won't compile since `Parens` (`(b; break)`) is compiled as `Value` and
-    # pure statement (`break`) can't be used in an expression.
-    # For this reasons, we return `Block` instead of `Parens`.
-    return base.unwrap() if base instanceof Parens and base.contains (n) -> n instanceof StatementLiteral
     @base           = base
     @properties     = props or []
     @[tag]          = yes if tag

src/nodes.coffee

@@ -1112,37 +1112,6 @@ test "#3921: `switch`", ->
     else "none"
   eq "five", c
 
-# Issue #3441: Parentheses wrapping expression throw invalid error in `then` clause
-test "#3441: `StatementLiteral` in parentheses", ->
-  i = 0
-  r1 = ((i++; break) while i < 10)
-  arrayEq r1, []
-
-  i = 0
-  r2 = ((i++; continue) while i < 10)
-  arrayEq r2, []
-
-  i = 0
-  r4 = while i < 10 then (i++; break)
-  arrayEq r4, []
-
-  i = 0
-  r5 = while i < 10 then (i++; continue)
-  arrayEq r5, []
-
-  arr = [0..9]
-  r6 = ((a; break) for a in arr)
-  arrayEq r6, []
-
-  r7 = ((a; continue) for a in arr)
-  arrayEq r7, []
-
-  r8 = for a in arr then (a; break)
-  arrayEq r8, []
-
-  r9 = for a in arr then (a; continue)
-  arrayEq r9, []
-
 # Issue #3909: backslash to break line in `for` loops throw syntax error
 test "#3909: backslash `for own ... of`", ->
 

test/control_flow.coffee

@@ -962,6 +962,42 @@ test "#4097: `yield return` as an expression", ->
         ^^^^^^^^^^^^
   '''
 
+test "#5013: `await return` as an expression", ->
+  assertErrorFormat '''
+    -> (await return)
+  ''', '''
+    [stdin]:1:5: error: cannot use a pure statement in an expression
+    -> (await return)
+        ^^^^^^^^^^^^
+  '''
+
+test "#5013: `return` as an expression", ->
+  assertErrorFormat '''
+    -> (return)
+  ''', '''
+    [stdin]:1:5: error: cannot use a pure statement in an expression
+    -> (return)
+        ^^^^^^
+  '''
+
+test "#5013: `break` as an expression", ->
+  assertErrorFormat '''
+    (b = 1; break) for b in a
+  ''', '''
+    [stdin]:1:9: error: cannot use a pure statement in an expression
+    (b = 1; break) for b in a
+            ^^^^^
+  '''
+
+test "#5013: `continue` as an expression", ->
+  assertErrorFormat '''
+    (b = 1; continue) for b in a
+  ''', '''
+    [stdin]:1:9: error: cannot use a pure statement in an expression
+    (b = 1; continue) for b in a
+            ^^^^^^^^
+  '''
+
 test "`&&=` and `||=` with a space in-between", ->
   assertErrorFormat '''
     a = 0