From c2a1cb956ad020ffa96845fefaec6b5679cb83e0 Mon Sep 17 00:00:00 2001
From: Irmen de Jong <irmen@razorvine.net>
Date: Mon, 8 Oct 2018 01:20:53 +0200
Subject: [PATCH] allow to re-assign string variables

---
 compiler/examples/test.p8             | 13 +++++++------
 compiler/src/prog8/ast/AstChecker.kt  | 11 +++++++----
 compiler/src/prog8/stackvm/StackVm.kt |  4 ++--
 3 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/compiler/examples/test.p8 b/compiler/examples/test.p8
index 6d8c6a80e..a36e1ccaa 100644
--- a/compiler/examples/test.p8
+++ b/compiler/examples/test.p8
@@ -6,13 +6,14 @@
 
 sub start() {
 
-    repeat {
-        _vm_write_str("333\n")
-    } until(1)
+    str s1 = "hello"
+    str s2 = "bye"
 
-    repeat {
-        _vm_write_str("444\n")
-    } until (0)
+    _vm_write_str(s1)
+    s1 = s2
+    _vm_write_str(s1)
+    s1 = "ciao"
+    _vm_write_str(s1)
 
     return
 
diff --git a/compiler/src/prog8/ast/AstChecker.kt b/compiler/src/prog8/ast/AstChecker.kt
index bb468fdf6..b20e42f2c 100644
--- a/compiler/src/prog8/ast/AstChecker.kt
+++ b/compiler/src/prog8/ast/AstChecker.kt
@@ -259,12 +259,9 @@ class AstChecker(private val namespace: INameScope,
         }
 
         // it is not possible to assign a new array to something.
-        // currently, it's also not possible to assign a new string to a string variable.
         when(assignment.value.resultingDatatype(namespace, heap)) {
-            DataType.STR, DataType.STR_P, DataType.STR_S, DataType.STR_PS ->
-                checkResult.add(SyntaxError("it's not possible to reassign a string", assignment.position))       // todo allow reassigning strings
             DataType.ARRAY, DataType.ARRAY_W, DataType.ARRAY_F, DataType.MATRIX ->
-                checkResult.add(SyntaxError("it's not possible to reassign an array", assignment.position))
+                checkResult.add(SyntaxError("it's not possible to assign an array literal value to something, use it as a variable decl initializer instead", assignment.position))
             else -> {}
         }
 
@@ -708,6 +705,8 @@ class AstChecker(private val namespace: INameScope,
                     return err("value '$number' out of range for unsigned word")
             }
             DataType.STR, DataType.STR_P, DataType.STR_S, DataType.STR_PS -> {
+                if(!value.isString)
+                    return err("string value expected")
                 val str = value.strvalue ?: heap.get(value.heapId!!).str!!
                 if (str.isEmpty() || str.length > 255)
                     return err("string length must be 1 to 255")
@@ -818,6 +817,10 @@ class AstChecker(private val namespace: INameScope,
             DataType.BYTE -> sourceDatatype==DataType.BYTE
             DataType.WORD -> sourceDatatype==DataType.BYTE || sourceDatatype==DataType.WORD
             DataType.FLOAT -> sourceDatatype==DataType.BYTE || sourceDatatype==DataType.WORD || sourceDatatype==DataType.FLOAT
+            DataType.STR -> sourceDatatype==DataType.STR
+            DataType.STR_S -> sourceDatatype==DataType.STR_S
+            DataType.STR_P -> sourceDatatype==DataType.STR_P
+            DataType.STR_PS -> sourceDatatype==DataType.STR_PS
             else -> checkResult.add(SyntaxError("cannot assign new value to variable of type $targetDatatype", position))
         }
 
diff --git a/compiler/src/prog8/stackvm/StackVm.kt b/compiler/src/prog8/stackvm/StackVm.kt
index df8d5944e..8787932ad 100644
--- a/compiler/src/prog8/stackvm/StackVm.kt
+++ b/compiler/src/prog8/stackvm/StackVm.kt
@@ -901,9 +901,9 @@ class StackVm(private var traceOutputFile: String?) {
             }
             Opcode.POP_VAR_W -> {
                 val value = evalstack.pop()
-                checkDt(value, setOf(DataType.WORD, DataType.ARRAY, DataType.ARRAY_W, DataType.ARRAY_F, DataType.STR, DataType.STR_P, DataType.STR_S, DataType.STR_PS, DataType.MATRIX))
+                checkDt(value, setOf(DataType.WORD, DataType.STR, DataType.STR_P, DataType.STR_S, DataType.STR_PS))
                 val variable = variables[ins.callLabel] ?: throw VmExecutionException("unknown variable: ${ins.callLabel}")
-                checkDt(variable, DataType.WORD)
+                checkDt(variable, setOf(DataType.WORD, DataType.STR, DataType.STR_P, DataType.STR_S, DataType.STR_PS))
                 variables[ins.callLabel!!] = value
             }
             Opcode.POP_VAR_F -> {