Merge pull request #1505 from DanielXMoore/for-by

Range loops can provide custom skip via `by` (not just in CoffeeScript)

civet.dev/reference.md

@@ -1835,6 +1835,11 @@ for i of [0...array.length]
   array[i] = array[i].toString()
 </Playground>
 
+<Playground>
+for i of [0...n] by 2
+  console.log i, "is even"
+</Playground>
+
 <Playground>
 for [1..5]
   attempt()

notes/Comparison-to-CoffeeScript.md

@@ -37,6 +37,8 @@ Things Kept from CoffeeScript
 - `when` inside `switch` automatically breaks
 - Multiple `,` separated `case`/`when` expressions
 - `else` → `default` in `switch`
+- `for ... when <condition>`
+- `for ... by <step>` when looping over range literals
 - Range literals `[0...10]`, `[a..b]`, `[x - 2 .. x + 2]`
 - Array slices `list[0...2]` → `list.slice(0, 2)`
 - Slice assignment `numbers[3..6] = [-3, -4, -5, -6]` → `numbers.splice(3, 4, ...[-3, -4, -5, -6])`
@@ -67,7 +69,6 @@ Civet.
 - `for from` (use JS `for of`, `"civet coffeeCompat"`, or `"civet coffeeForLoops"`)
 - `for in` (use `for each of`, or `"civet coffeeCompat"`, or `"civet coffeeForLoops"`)
 - `for own of` (use `for own in`, or `"civet coffeeCompat"`, or `"civet coffeeForLoops"`)
-- `for ... when <condition>` (use `continue if exp` inside loop, `"civet coffeeCompat"`, or `"civet coffeeForLoops"`)
 - `a ? b` (use `a ?? b`, though it doesn't check for undeclared variables; `"civet coffeeCompat"`, or `"civet coffeeBinaryExistential"` enables `a ? b` at the cost of losing JS ternary operator)
 - `a of b` (use `a in b` as in JS, or `"civet coffeeCompat"`, or `"civet coffeeOf"`)
 - `a not of b` (use `a not in b`, or `"civet coffeeCompat"`, or `"civet coffeeOf"`)

source/generate.civet

@@ -64,13 +64,17 @@ function gen(root: ASTNode, options: Options): string
           offset
         return ""
 
-      if node.$loc?
+      if "$loc" in node
         {token, $loc} := node
-        updateSourceMap? token, $loc.pos
+        updateSourceMap? token, $loc.pos if $loc?
         //console.log 'set', node, options.sourceMap.data.srcLine, options.sourceMap.data.srcColumn if options?.sourceMap?
         return token
 
-      if !node.children
+      unless node.children
+        // Occasionally we create ASTLeaf nodes with no $loc field
+        if node.token?
+          return node.token
+
         switch node.type
           when "Ref"
             throw new Error(`Unpopulated ref ${stringify node}`)

source/parser.hera

@@ -394,7 +394,7 @@ ForbiddenImplicitCalls
 
 # Binary operators that are reserved in that context
 ReservedBinary
-  /(as|of|satisfies|then|when|implements|xor|xnor)(?!\p{ID_Continue}|[\u200C\u200D$])/
+  /(as|of|by|satisfies|then|when|implements|xor|xnor)(?!\p{ID_Continue}|[\u200C\u200D$])/
 
 ArgumentsWithTrailingMemberExpressions
   Arguments:args AllowedTrailingMemberExpressions:trailing ->
@@ -4550,7 +4550,7 @@ ForStatementControlWithWhen
     }
     return {
       ...control,
-      blockPrefix: [...control.blockPrefix,
+      blockPrefix: [...control.blockPrefix ?? [],
         ["", {
           type: "IfStatement",
           then: block,
@@ -4606,7 +4606,7 @@ CoffeeForStatementParameters
       const lenRef = makeRef("len")
 
       if (exp.type === "RangeExpression") {
-        return forRange(open, declaration, exp, step?.[2], close)
+        return forRange(open, declaration, exp, step && prepend(trimFirstSpace(step[0]), trimFirstSpace(step[2])), close)
       }
 
       // If exp isn't a simple identifier use a ref
@@ -4718,10 +4718,10 @@ ForStatementParameters
   # NOTE: Consolidated declarations
   # NOTE: Consolidated optional 'await'
   ( Await __ )? ( (Each / Own) __ )? ( OpenParen __ ) ForInOfDeclaration ( __ Comma __ ForInOfDeclaration )? __ ( In / Of ) ExpressionWithObjectApplicationForbidden ( __ By ExpressionWithObjectApplicationForbidden )? ( __ CloseParen ) ->
-    return processForInOf($0, getHelperRef)
+    return processForInOf($0)
   # NOTE: Added optional parens
   ( Await __ )? ( (Each / Own) __ )? InsertOpenParen ForInOfDeclaration ( __ Comma __ ForInOfDeclaration )? __ ( In / Of ) ExpressionWithObjectApplicationForbidden ( __ By ExpressionWithObjectApplicationForbidden )? InsertCloseParen ->
-    return processForInOf($0, getHelperRef)
+    return processForInOf($0)
   ForRangeParameters
 
 ForRangeParameters
@@ -6673,7 +6673,7 @@ JSXImplicitFragment
       ],
       jsxChildren: [$1].concat($2.map(([, tag]) => tag)),
     }
-    const type = typeOfJSX(jsx, config, getHelperRef)
+    const type = typeOfJSX(jsx, config)
     return type ? [
       { ts: true, children: ["("] },
       jsx,

source/parser/for.civet

@@ -6,19 +6,26 @@ import type {
   Children
   RangeDots
   RangeExpression
+  Whitespace
 } from ./types.civet
 
 import {
-  insertTrimmingSpace
   literalValue
   makeLeftHandSideExpression
+  makeNumericLiteral
+  prepend
+  trimFirstSpace
 } from ./util.civet
 
 import {
   makeRef
   maybeRef
 } from ./ref.civet
 
+import {
+  getHelperRef
+} from ./helper.civet
+
 function processRangeExpression(start: ASTNode, ws1: ASTNode, range: RangeDots, end: ASTNode)
   ws1 = [ws1, range.children[0]] // whitespace before ..
   ws2 := range.children[1]       // whitespace after ..
@@ -127,17 +134,21 @@ function forRange(
 
   let stepRef, asc: boolean?
   if stepExp
-    stepExp = insertTrimmingSpace(stepExp, "")
+    stepExp = trimFirstSpace(stepExp)
     stepRef = maybeRef(stepExp, "step")
   else if infinite
-    stepExp = stepRef = "1"
+    stepExp = stepRef = makeNumericLiteral 1
   else if increasing?
     if increasing
-      stepExp = stepRef = "1"
+      stepExp = stepRef = makeNumericLiteral 1
       asc = true
     else
-      stepExp = stepRef = "-1"
+      stepExp = stepRef = makeNumericLiteral -1
       asc = false
+  stepValue := if stepExp?.type is "Literal"
+    try literalValue stepExp // ignore invalid literals
+  if stepValue <? "number"
+    asc = stepValue > 0
 
   // start needs to be ref'd to compute start <= end, unless we know direction
   startRef .= if stepRef then start else maybeRef(start, "start")
@@ -153,15 +164,16 @@ function forRange(
       . stepRef
 
   let ascDec: ASTNode[] = [], ascRef
-  if stepRef
+  if stepExp
     unless stepRef is stepExp
       ascDec = [", ", stepRef, " = ", stepExp]
 
-  else if "Literal" is start.type is end.type
+  else if start?.type is "Literal" is end?.type
+    // @ts-ignore Allow comparison of any literal values, as in JS
     asc = literalValue(start) <= literalValue(end)
     if "StringLiteral" is start.subtype is end.subtype
-      startRef = literalValue(start).charCodeAt(0).toString()
-      endRef = literalValue(end).charCodeAt(0).toString()
+      startRef = (literalValue(start) as string).charCodeAt(0).toString()
+      endRef = (literalValue(end) as string).charCodeAt(0).toString()
 
   else
     ascRef = makeRef("asc")
@@ -171,7 +183,7 @@ function forRange(
   if forDeclaration?.declare // var/let/const declaration of variable
     if forDeclaration.declare.token is "let"
       varName := forDeclaration.children.splice(1)  // strip let
-      varAssign = [...insertTrimmingSpace(varName, ""), " = "]
+      varAssign = [...trimFirstSpace(varName), " = "]
       varLet = [",", ...varName, " = ", counterRef]
     else // const or var: put inside loop
       // TODO: missing indentation
@@ -192,14 +204,14 @@ function forRange(
     : [counterRef, " < ", endRef, " : ", counterRef, " > ", endRef]
 
   condition :=
-    infinite ? [] :
+    infinite or stepValue is 0 ? [] :
     asc? ? (asc ? counterPart[0...3] : counterPart[4..]) :
     stepRef ? [stepRef, " !== 0 && (", stepRef, " > 0 ? ", ...counterPart, ")"] :
     [ascRef, " ? ", ...counterPart]
 
   increment :=
-    stepRef === "1" ? [...varAssign, "++", counterRef] :
-    stepRef === "-1" ? [...varAssign, "--", counterRef] :
+    stepValue is +1 ? [...varAssign, "++", counterRef] :
+    stepValue is -1 ? [...varAssign, "--", counterRef] :
     stepRef
       ? [...varAssign, counterRef, " += ", stepRef]
       : ascRef
@@ -213,22 +225,25 @@ function forRange(
   }
 
 function processForInOf($0: [
-  awaits: ASTNode,
-  eachOwn: undefined | [ASTLeaf, ASTNode],
-  open: ASTNode,
-  declaration: ASTNode,
-  declaration2: [ws1: ASTNode, comma: ASTLeaf, ws2: ASTNode, decl2: ASTNode],
-  ws: ASTNode,
-  inOf: ASTLeaf,
-  exp: ASTNodeBase,
-  step: ASTNode,
-  close: ASTNode
-], getRef)
+  awaits: ASTNode
+  eachOwn: [ASTLeaf, ASTNode] | undefined
+  open: ASTLeaf
+  declaration: ASTNode
+  declaration2: [ws1: ASTNode, comma: ASTLeaf, ws2: ASTNode, decl2: ASTNode]
+  ws: ASTNode
+  inOf: ASTLeaf
+  exp: ASTNodeBase
+  step: [Whitespace, ASTLeaf, ASTNode]
+  close: ASTLeaf
+])
   [awaits, eachOwn, open, declaration, declaration2, ws, inOf, exp, step, close] .= $0
 
   if exp.type is "RangeExpression" and inOf.token is "of" and !declaration2
     // TODO: add support for `declaration2` to efficient `forRange`
-    return forRange(open, declaration, exp, step, close)
+    return forRange
+      open, declaration, exp
+      step and prepend(trimFirstSpace(step[0]), trimFirstSpace(step[2])) // omit "by" token
+      close
   else if step
     throw new Error("for..of/in cannot use 'by' except with range literals")
 
@@ -248,24 +263,24 @@ function processForInOf($0: [
       if declaration2
         const [, , ws2, decl2] = declaration2  // strip __ Comma __
         blockPrefix.push(["", [
-          insertTrimmingSpace(ws2, ""), decl2, " = ", counterRef
+          trimFirstSpace(ws2), decl2, " = ", counterRef
         ], ";"])
         assignmentNames.push(...decl2.names)
 
       expRefDec := (expRef !== exp)
         // Trim a single leading space if present
-        ? [insertTrimmingSpace(expRef, " "), " = ", insertTrimmingSpace(exp, ""), ", "]
+        ? [trimFirstSpace(expRef), " = ", trimFirstSpace(exp), ", "]
         : []
 
       blockPrefix.push ["", {
         type: "Declaration"
-        children: [declaration, " = ", insertTrimmingSpace(expRef, ""), "[", counterRef, "]"]
+        children: [declaration, " = ", trimFirstSpace(expRef), "[", counterRef, "]"]
         names: assignmentNames
       }, ";"]
 
       declaration =
         type: "Declaration"
-        children: ["let ", ...expRefDec, counterRef, " = 0, ", lenRef, " = ", insertTrimmingSpace(expRef, ""), ".length"]
+        children: ["let ", ...expRefDec, counterRef, " = 0, ", lenRef, " = ", trimFirstSpace(expRef), ".length"]
         names: []
 
       condition := [counterRef, " < ", lenRef, "; "]
@@ -317,7 +332,7 @@ function processForInOf($0: [
     return {
       declaration
       blockPrefix
-      children: [awaits, eachOwnError, open, declaration, ws, inOf, expRef ?? exp, step, close] // omit declaration2, replace eachOwn with eachOwnError, replace exp with expRef
+      children: [awaits, eachOwnError, open, declaration, ws, inOf, expRef ?? exp, close] // omit declaration2, replace eachOwn with eachOwnError, replace exp with expRef
     }
 
   let ws2: ASTNode?, decl2: ASTNode?
@@ -333,7 +348,7 @@ function processForInOf($0: [
       }
       blockPrefix.push ["", {
         type: "Declaration"
-        children: [insertTrimmingSpace(ws2, ""), decl2, " = ", counterRef, "++"]
+        children: [trimFirstSpace(ws2), decl2, " = ", counterRef, "++"]
         names: decl2.names
       }, ";"]
 
@@ -350,12 +365,12 @@ function processForInOf($0: [
           children: [" ", expRef, " =", exp]
       // for own..in
       if own
-        const hasPropRef = getRef("hasProp")
-        blockPrefix.push ["", ["if (!", hasPropRef, "(", insertTrimmingSpace(expRef, ""), ", ", insertTrimmingSpace(pattern, ""), ")) continue"], ";"]
+        hasPropRef := getHelperRef("hasProp")
+        blockPrefix.push ["", ["if (!", hasPropRef, "(", trimFirstSpace(expRef), ", ", trimFirstSpace(pattern), ")) continue"], ";"]
       if decl2
         blockPrefix.push ["", {
           type: "Declaration"
-          children: [insertTrimmingSpace(ws2, ""), decl2, " = ", insertTrimmingSpace(expRef, ""), "[", insertTrimmingSpace(pattern, ""), "]"]
+          children: [trimFirstSpace(ws2), decl2, " = ", trimFirstSpace(expRef), "[", trimFirstSpace(pattern), "]"]
           names: decl2.names
         }, ";"]
 
@@ -364,7 +379,7 @@ function processForInOf($0: [
 
   return {
     declaration,
-    children: [awaits, eachOwnError, open, declaration, ws, inOf, exp, step, close], // omit declaration2, replace each with eachOwnError
+    children: [awaits, eachOwnError, open, declaration, ws, inOf, exp, close], // omit declaration2, replace each with eachOwnError
     blockPrefix,
     hoistDec,
   }

source/parser/types.civet

@@ -104,7 +104,6 @@ export type OtherNode =
   | PinProperty
   | Placeholder
   | PropertyAccess
-  | RangeDots
   | RangeExpression
   | ReturnValue
   | SliceExpression
@@ -158,6 +157,9 @@ export type ASTLeaf =
   parent?: Parent
   children?: never
 
+export type ASTLeafWithType<T extends string> =
+  Exclude<ASTLeaf, "type"> & { type: T }
+
 export type CommentNode =
   type: "Comment"
   $loc: Loc
@@ -172,6 +174,7 @@ export type BinaryOp = (string &
   assoc?: never
   type?: undefined
 ) | (ASTLeaf &
+  type?: undefined
   special?: true
   // The following are allowed only when special is true:
   prec?: string | number | undefined
@@ -951,13 +954,13 @@ export type FieldDefinition
 export type Literal =
   type: "Literal"
   subtype?: "NumericLiteral" | "StringLiteral"
-  children: Children & [ LiteralContentNode ]
+  children: Children & LiteralContentNode[]
   parent?: Parent
   raw: string
 
-export type LiteralContentNode = ASTLeaf & {
-  type?: "NumericLiteral" | "StringLiteral"
-}
+export type LiteralContentNode =
+  | ASTLeaf
+  | ASTLeafWithType "NumericLiteral" | "StringLiteral"
 
 export type RangeExpression
   type: "RangeExpression"
@@ -1053,7 +1056,7 @@ export type TypeLiteral =
   children: Children
   parent?: Parent
 
-export type VoidType = ASTLeaf & type: "VoidType"
+export type VoidType = ASTLeafWithType "VoidType"
 
 export type TypeLiteralNode = ASTLeaf | VoidType