while-continue with labels and docs/tests

library/src/commonMain/kotlin/net/sergeych/ling/Compiler.kt

@@ -305,6 +305,7 @@ class Compiler {
         "var" -> parseVarDeclaration(id.value, true, cc)
         "while" -> parseWhileStatement(cc)
         "break" -> parseBreakStatement(id.pos, cc)
+        "continue" -> parseContinueStatement(id.pos, cc)
         "fn", "fun" -> parseFunctionDeclaration(cc)
         "if" -> parseIfStatement(cc)
         else -> null
@@ -388,6 +389,27 @@ class Compiler {
         }
     }
 
+    private fun parseContinueStatement(start: Pos, cc: CompilerContext): Statement {
+        val t = cc.next()
+
+        val label = if (t.pos.line != start.line || t.type != Token.Type.ATLABEL) {
+            cc.previous()
+            null
+        } else {
+            t.value
+        }?.also {
+            // check that label is defined
+            cc.ensureLabelIsValid(start, it)
+        }
+
+        return statement(start) {
+            throw LoopBreakContinueException(
+                doContinue = true,
+                label = label,
+            )
+        }
+    }
+
     private fun ensureRparen(tokens: CompilerContext): Pos {
         val t = tokens.next()
         if (t.type != Token.Type.RPAREN)