prepare parser to be more flexible with array indexed expressions

compilerAst/src/prog8/ast/antlr/Antlr2Kotlin.kt

@@ -8,6 +8,7 @@ import prog8.ast.expressions.*
 import prog8.ast.statements.*
 import prog8.code.core.*
 import prog8.parser.Prog8ANTLRParser
+import prog8.parser.Prog8ANTLRParser.*
 import kotlin.io.path.Path
 import kotlin.io.path.isRegularFile
 
@@ -310,12 +311,18 @@ private fun Prog8ANTLRParser.Sub_paramsContext.toAst(): List<SubroutineParameter
         }
 
 private fun Prog8ANTLRParser.Assign_targetContext.toAst() : AssignTarget {
-    val identifier = scoped_identifier()
-    return when {
-        identifier!=null -> AssignTarget(identifier.toAst(), null, null, toPosition())
-        arrayindexed()!=null -> AssignTarget(null, arrayindexed().toAst(), null, toPosition())
-        directmemory()!=null -> AssignTarget(null, null, DirectMemoryWrite(directmemory().expression().toAst(), toPosition()), toPosition())
-        else -> AssignTarget(scoped_identifier()?.toAst(), null, null, toPosition())
+    return when(this) {
+        is IdentifierTargetContext ->
+            AssignTarget(scoped_identifier().toAst(), null, null, scoped_identifier().toPosition())
+        is MemoryTargetContext ->
+            AssignTarget(null, null, DirectMemoryWrite(directmemory().expression().toAst(), directmemory().toPosition()), toPosition())
+        is ArrayindexedTargetContext -> {
+            val arrayvar = scoped_identifier().toAst()
+            val index = arrayindex().toAst()
+            val arrayindexed = ArrayIndexedExpression(arrayvar, index, scoped_identifier().toPosition())
+            AssignTarget(null, arrayindexed, null, toPosition())
+        }
+        else -> throw FatalAstException("weird assign target node $this")
     }
 }
 
@@ -427,6 +434,12 @@ private fun Prog8ANTLRParser.ExpressionContext.toAst() : Expression {
         }
     }
 
+    if(arrayindex()!=null) {
+        val identifier = scoped_identifier().toAst()
+        val index = arrayindex().toAst()
+        return ArrayIndexedExpression(identifier, index, scoped_identifier().toPosition())
+    }
+
     if(scoped_identifier()!=null)
         return scoped_identifier().toAst()
 
@@ -448,9 +461,6 @@ private fun Prog8ANTLRParser.ExpressionContext.toAst() : Expression {
     if(childCount==3 && children[0].text=="(" && children[2].text==")")
         return expression(0).toAst()        // expression within ( )
 
-    if(arrayindexed()!=null)
-        return arrayindexed().toAst()
-
     if(typecast()!=null)
         return TypecastExpression(expression(0).toAst(), typecast().datatype().toAst(), false, toPosition())
 
@@ -497,12 +507,6 @@ private fun Prog8ANTLRParser.StringliteralContext.toAst(): StringLiteral {
     }
 }
 
-private fun Prog8ANTLRParser.ArrayindexedContext.toAst(): ArrayIndexedExpression {
-    return ArrayIndexedExpression(scoped_identifier().toAst(),
-            arrayindex().toAst(),
-            toPosition())
-}
-
 private fun Prog8ANTLRParser.Expression_listContext.toAst() = expression().map{ it.toAst() }
 
 private fun Prog8ANTLRParser.Scoped_identifierContext.toAst() : IdentifierReference =

docs/source/todo.rst

@@ -1,6 +1,8 @@
 TODO
 ====
 
+- allow 'chained' array indexing for expressions:  value = ptrarray[0][0]
+- allow 'chained' array indexing for assign targets:  ptrarray[0][0] = 42   this is just evaluating the lhs as a uword pointer expression
 - [on branch:] investigate McCarthy evaluation again? this may also reduce code size perhaps for things like if a>4 or a<2 ....
 - IR: reduce the number of branch instructions such as BEQ, BEQR, etc (gradually), replace with CMP(I) + status branch instruction
 - IR: reduce amount of CMP/CMPI after instructions that set the status bits correctly (LOADs? INC? etc), but only after setting the status bits is verified!

parser/antlr/Prog8ANTLR.g4

@@ -152,9 +152,9 @@ augassignment :
 	;
 
 assign_target:
-	scoped_identifier
-	| arrayindexed
-	| directmemory
+	scoped_identifier               #IdentifierTarget
+	| scoped_identifier arrayindex  #ArrayindexedTarget        // TODO expression instead of just scoped_identifier
+	| directmemory                  #MemoryTarget
 	;
 
 postincrdecr :  assign_target  operator = ('++' | '--') ;
@@ -180,7 +180,7 @@ expression :
 	| left = expression EOL? bop = 'xor' EOL? right = expression
 	| literalvalue
 	| scoped_identifier
-	| arrayindexed
+	| scoped_identifier arrayindex          // TODO expression instead of just scoped_identifier
 	| directmemory
 	| addressof
 	| expression typecast
@@ -188,8 +188,6 @@ expression :
 
 typecast : 'as' datatype;
 
-arrayindexed :  scoped_identifier arrayindex  ;
-
 directmemory : '@' '(' expression ')';
 
 addressof : <assoc=right> ADDRESS_OF scoped_identifier ;