Enforce whitespace around binary operators

effekt/shared/src/main/scala/effekt/Parser.scala

@@ -1001,6 +1001,7 @@ class Parser(tokens: Seq[Token], source: Source) {
     nonterminal:
       var left = nonTerminal()
       while (ops.contains(peek.kind)) {
+         checkBinaryOpWhitespace()
          val op = next()
          val right = nonTerminal()
          left = binaryOp(left, op, right)
@@ -1053,6 +1054,34 @@ class Parser(tokens: Seq[Token], source: Source) {
   def TypeTuple(tps: Many[Type]): Type =
     TypeRef(IdRef(List("effekt"), s"Tuple${tps.size}", tps.span.synthesized), tps, tps.span.synthesized)
 
+  // Check that the current token is surrounded by whitespace.
+  // If not, soft fail.
+  //
+  // NOTE: Ideally, we'd reintroduce whitespace tokens and then just check here that
+  //       the tokens at `position - 1` and `position + 1` are in fact, `isSpace`.
+  //       But as of writing this, lexer doesn't even report whitespace tokens, so they never reach here.
+  private def checkBinaryOpWhitespace(): Unit = {
+    val opToken = peek
+    val opStart = opToken.start
+    val opEnd = opToken.end
+
+    // Check character immediately before operator
+    val wsBefore = opStart > 0 && {
+      val charBefore = source.content.charAt(opStart - 1)
+      charBefore.isWhitespace
+    }
+
+    // Check character immediately after operator
+    val wsAfter = opEnd + 1 < source.content.length && {
+      val charAfter = source.content.charAt(opEnd + 1)
+      charAfter.isWhitespace
+    }
+
+    if (!wsBefore || !wsAfter) {
+      softFail(s"Missing whitespace around binary operator", position, position)
+    }
+  }
+
   /**
    * This is a compound production for
    *  - member selection <EXPR>.<NAME>

examples/benchmarks/are_we_fast_yet/nbody.effekt

@@ -92,9 +92,9 @@ def run(n: Int) = {
     def offsetMomentum(body: Body, px: Double, py: Double, pz: Double) =
       Body(
         body.x, body.y, body.z,
-        0.0 -(px / SOLAR_MASS),
-        0.0 -(py / SOLAR_MASS),
-        0.0 -(pz / SOLAR_MASS),
+        0.0 - (px / SOLAR_MASS),
+        0.0 - (py / SOLAR_MASS),
+        0.0 - (pz / SOLAR_MASS),
         body.mass)
 
     bodies.unsafeSet(0, sun.offsetMomentum(px, py, pz))

examples/llvm/gids.effekt

@@ -22,6 +22,6 @@ def main() = region r {
         println(g())
         println(h())
     } with GID {
-        def gid() = { n = n+1; resume(n) }
+        def gid() = { n = n + 1; resume(n) }
     }
 }

examples/llvm/localfunctionasargument.effekt

@@ -3,10 +3,10 @@ def hof(x: Int){ f: Int => Int }: Int = {
 }
 
 def foo(a: Int) = {
-    def bar(b: Int): Int = b*a
+    def bar(b: Int): Int = b * a
     hof(5){bar}
 }
 
-def main() = { 
+def main() = {
     println(foo(2))
 }

examples/llvm/polymorphic_failtooption.effekt

@@ -22,7 +22,7 @@ def safeDiv(x: Int, y: Int): Int / Fail = {
     if (y == 0){
         do Fail(); 0
     } else {
-        x/y
+        x / y
     }
 }
 

examples/llvm/polymorphism_data.effekt

@@ -15,24 +15,24 @@ def map[A,B](l: List[A]){ f: A => B }: List[B] = {
 
 def show(i: Int): String = {
   def impl_digit(i: Int): String = {
-    if(i==0){"0"} else
-    if(i==1){"1"} else
-    if(i==2){"2"} else
-    if(i==3){"3"} else
-    if(i==4){"4"} else
-    if(i==5){"5"} else
-    if(i==6){"6"} else
-    if(i==7){"7"} else
-    if(i==8){"8"} else
-    if(i==9){"9"} else
+    if(i == 0){"0"} else
+    if(i == 1){"1"} else
+    if(i == 2){"2"} else
+    if(i == 3){"3"} else
+    if(i == 4){"4"} else
+    if(i == 5){"5"} else
+    if(i == 6){"6"} else
+    if(i == 7){"7"} else
+    if(i == 8){"8"} else
+    if(i == 9){"9"} else
     "?"
   }
   def impl(i: Int): String = {
-    if(i<10){impl_digit(i)}else{
-      impl(i/10) ++ impl_digit(mod(i,10))
+    if(i < 10){impl_digit(i)}else{
+      impl(i / 10) ++ impl_digit(mod(i, 10))
     }
   }
-  if(i==0) {
+  if(i == 0) {
     "0"
   } else {
     impl(i)

examples/pos/doubles.effekt

@@ -2,7 +2,7 @@ def main() = {
     println(1.2 + 2.0 * 3.0 / 4.0 + 1.4);
     println(toInt(1.5));
     println(round(1.5));
-    println(toDouble(2)+ 0.1);
+    println(toDouble(2) + 0.1);
     println(floor(1.7));
     println(ceil(2.1));
 }

examples/pos/issue661.effekt

@@ -15,7 +15,7 @@ def my_map[T, U] {action: () => Unit / {Iter[T]}} {f: T => U}: Unit / {Iter[U]}
   }
 
 def main() =
-  try my_map { iter([1, 2, 3]) } { x => x+1 }
+  try my_map { iter([1, 2, 3]) } { x => x + 1 }
   with Iter[Int] {
     def yield(x) = { println(x); resume(()) }
   }

libraries/common/random.effekt

@@ -170,7 +170,7 @@ def main() = {
       val b = randomInt(0, 9)
       val c = randomInt(0, 9)
       println(a.show ++ " " ++ b.show ++ " " ++ c.show)
-      println(a*100 + b*10 + c)
+      println(a * 100 + b * 10 + c)
     }
   }