Merge pull request #1592 from DanielXMoore/range-assign

Fix range `for` loop with complex left-hand side

source/parser/for.civet

@@ -1,4 +1,5 @@
 import type {
+  AssignmentExpression
   ASTNode
   ASTNodeObject
   ASTLeaf
@@ -184,23 +185,20 @@ function forRange(
     ascDec = [", ", ascRef, " = ", startRef, " <= ", endRef]
 
   let varAssign: ASTNode[] = [], varLetAssign = varAssign, varLet = varAssign, blockPrefix
-  let names: string[] = forDeclaration?.names
-  if forDeclaration?.decl // var/let/const declaration of variable
-    if forDeclaration.decl is "let"
+  let names: string[] = forDeclaration?.names ?? []
+  if forDeclaration?
+    if forDeclaration.type is "AssignmentExpression" // Coffee-style for loop
+      varAssign = varLetAssign = [forDeclaration, " = "]
+      names = [] // assigned but not declared
+    else if forDeclaration.decl is "let" // let: declare within loop
       varName := forDeclaration.children.splice(1)  // strip let
-      varAssign = [...trimFirstSpace(varName), " = "]
+      varAssign = [...trimFirstSpace(varName) as ASTNode[], " = "]
       varLet = [",", ...varName, " = ", counterRef]
-    else // const or var: put inside loop
-      // TODO: missing indentation
+    else // const or var or assignment like `for x[y] of z`: put inside loop
       value := "StringLiteral" is start.subtype ? ["String.fromCharCode(", counterRef, ")"] : counterRef
       blockPrefix = [
         ["", [forDeclaration, " = ", value], ";"]
       ]
-  else if forDeclaration // Coffee-style for loop
-    assert.equal forDeclaration.type, "AssignmentExpression",
-      "Internal error: Coffee-style for loop must be an assignment expression"
-    varAssign = varLetAssign = [forDeclaration, " = "]
-    names = [] // assigned but not declared
 
   declaration := {
     type: "Declaration"

test/for.civet

@@ -159,6 +159,14 @@ describe "for", ->
     }
   """
 
+  testCase """
+    range with access assignment
+    ---
+    for chosen[i] of [0...10]
+    ---
+    for (let i1 = 0; i1 < 10; ++i1) {chosen[i] = i1;;}
+  """
+
   testCase """
     infinite range
     ---