Fix parsing of nested implied indentations with ...

Author: LPTK

hkmc2/shared/src/main/scala/hkmc2/syntax/Lexer.scala

@@ -368,12 +368,19 @@ class Lexer(origin: Origin, dbg: Bool)(using raise: Raise):
   /** Converts the lexed tokens into structured tokens. */
   lazy val bracketedTokens: Ls[Stroken -> Loc] =
     import BracketKind._
-    def go(toks: Ls[Token -> Loc], canStartAngles: Bool, stack: Ls[BracketKind -> Loc -> Ls[Stroken -> Loc]], acc: Ls[Stroken -> Loc]): Ls[Stroken -> Loc] =
+    def go(
+        toks: Ls[Token -> Loc],
+        canStartAngles: Bool,
+        stack: Ls[BracketKind -> Loc -> Ls[Stroken -> Loc]],
+        acc: Ls[Stroken -> Loc],
+    ): Ls[Stroken -> Loc] =
       toks match
         case (SUSPENSION(true), l0) :: Nil =>
+          // * This is an ugly special-case to handle things like `module M with ...`
+          // * where there is no actual body after the `...`.
+          // * It can't be handled in the parser because this is only valid at the top-level,
+          // * not within brackets, as in `(arg0, ...) => blah`.
           go(OPEN_BRACKET(Indent) -> l0 :: LITVAL(Tree.UnitLit(true)) -> l0 :: Nil, false, stack, acc)
-        case (SUSPENSION(true), l0) :: (NEWLINE, l1) :: rest =>
-          go(OPEN_BRACKET(Indent) -> (l0 ++ l1) :: rest, false, stack, acc)
         case (QUOTE, l0) :: (IDENT("<", true), l1) :: rest =>
           go(rest, false, stack, (IDENT("<", true), l1) :: (QUOTE, l0) :: acc)
         case (QUOTE, l0) :: (IDENT(">", true), l1) :: rest =>

hkmc2/shared/src/main/scala/hkmc2/syntax/Parser.scala

@@ -126,7 +126,19 @@ abstract class Parser(
     doPrintDbg("│ " * this.indent + msg)
 
   protected var indent = 0
-  private var _cur: Ls[TokLoc] = tokens
+  private var _cur: Ls[TokLoc] = expandSuspensions(tokens)
+  
+  // * Expands end-of-line suspensions that introduce implied indentation.
+  private def expandSuspensions(tokens: Ls[TokLoc]): Ls[TokLoc] = tokens match
+    case (SUSPENSION(true), l0) :: (NEWLINE, l1) :: rest =>
+      val outerLoc = l0.left ++ rest.lastOption.map(_._2.right)
+      val innerLoc = l1.right ++ rest.lastOption.map(_._2.left)
+      BRACKETS(Indent, expandSuspensions(rest))(innerLoc) -> outerLoc :: Nil
+    case tl :: rest =>
+      val rest2 = expandSuspensions(rest)
+      if rest2 is rest then tokens
+      else tl :: rest2
+    case Nil => tokens
 
   private def wrap[R](args: => Any)(using l: Line, n: Name)(mkRes: => R): R =
     printDbg(s"@ ${n.value}${args match {

hkmc2/shared/src/test/mlscript/parser/Suspension.mls

@@ -1,37 +1,35 @@
-:parseOnly
+:js
 
 
-log of ...
+print of ...
 123
-//│ Parsed:
-//│ 	App(Ident(log),Tup(List(IntLit(123))))
+//│ > 123
 
-log of...
+print of...
 123
-//│ Parsed:
-//│ 	App(Ident(log),Tup(List(IntLit(123))))
+//│ > 123
 
-log of
+print of
   123
-//│ Parsed:
-//│ 	App(Ident(log),Tup(List(IntLit(123))))
+//│ > 123
+
+
+if true do...
+
+if true do...
+1
+//│ = 1
 
 
 module Option with ...
-//│ Parsed:
-//│ 	TypeDef(Mod,Ident(Option),None,Some(Block(List(UnitLit(true)))))
 
 module Option with ...
 val a = 1
-//│ Parsed:
-//│ 	TypeDef(Mod,Ident(Option),None,Some(Block(List(TermDef(ImmutVal,Ident(a),Some(IntLit(1)))))))
 
 module Option with ...
 // 
 val a = 1
 // 
-//│ Parsed:
-//│ 	TypeDef(Mod,Ident(Option),None,Some(Block(List(TermDef(ImmutVal,Ident(a),Some(IntLit(1)))))))
 
 :pt
 module A with
@@ -41,6 +39,7 @@ module A with
   val a = 1
 
   val b = 2
+  
 //│ Parsed tree:
 //│ TypeDef:
 //│   k = Mod
@@ -62,4 +61,42 @@ module A with
 //│           rhs = S of IntLit of 2
 
 
+fun test(x) =
+  if x then print("ok") else...
+  print("ko")
+let foo = 1
+//│ foo = 1
+
+
+:w
+x =>
+  if false then 0 else...
+  1
+let bar = 1
+//│ ╔══[WARNING] Pure expression in statement position
+//│ ║  l.72: 	x =>
+//│ ║        	^^^^
+//│ ║  l.73: 	  if false then 0 else...
+//│ ║        	^^^^^^^^^^^^^^^^^^^^^^^^^
+//│ ║  l.74: 	  1
+//│ ╙──      	^^^
+//│ bar = 1
+
+bar
+//│ = 1
+
+
+:w
+:e
+x => if false then 0 else...
+  1
+let foo = 1
+//│ ╔══[ERROR] Illegal position for '...' spread operator.
+//│ ║  l.92: 	  1
+//│ ╙──      	  ^
+//│ ╔══[WARNING] Pure expression in statement position
+//│ ║  l.91: 	x => if false then 0 else...
+//│ ╙──      	^
+//│ foo = 1
+