Change annotations parsing in bodies of operators

This change only matters in cases of if/when/for/while having braceless
blocks

Annotations on them are parsed now as on block-level expressions, i.e.
they're attached to the whole expression

grammar/src/control.grm

@@ -4,8 +4,13 @@
 See [Control structures](control-flow.html)
 */
 
+controlStructureBody
+  : block
+  : blockLevelExpression
+  ;
+
 if
-  : "if" "(" expression ")" expression SEMI? ("else" expression)?
+  : "if" "(" expression ")" controlStructureBody SEMI? ("else" controlStructureBody)?
   ;
 
 try
@@ -27,13 +32,13 @@ loop
   ;
 
 for
-  : "for" "(" annotations (multipleVariableDeclarations | variableDeclarationEntry) "in" expression ")" expression
+  : "for" "(" annotations (multipleVariableDeclarations | variableDeclarationEntry) "in" expression ")" controlStructureBody
   ;
 
 while
-  : "while" "(" expression ")" expression
+  : "while" "(" expression ")" controlStructureBody
   ;
 
 doWhile
-  : "do" expression "while" "(" expression ")"
+  : "do" controlStructureBody "while" "(" expression ")"
   ;

grammar/src/expressions.grm

@@ -172,6 +172,10 @@ declaration
 
 statement
   : declaration
+  : blockLevelExpression
+  ;
+
+blockLevelExpression
   : annotations expression
   ;
 

grammar/src/when.grm

@@ -12,12 +12,12 @@ when
 
 // TODO : consider empty after ->
 whenEntry
-  : whenCondition{","} "->" expression SEMI
-  : "else" "->" expression SEMI
+  : whenCondition{","} "->" controlStructureBody SEMI
+  : "else" "->" controlStructureBody SEMI
   ;
 
 whenCondition
   : expression
   : ("in" | "!in") expression
   : ("is" | "!is") isRHS
-  ;
+  ;