feat: allow primitive String type to be used in arc4 methods

examples/sizes.txt

@@ -1,5 +1,5 @@
   Name                                         O0 size   O1 size   O1 ⏷   O2 size   O2 ⏷ 
-  abi_routing/Reference                           1179      1019    160      1019      0 
+  abi_routing/Reference                           1237      1076    161      1076      0 
   amm/ConstantProductAMM                          1213      1113    100      1113      0 
   application/Reference                            175       168      7       168      0 
   arc-28/EventEmitter                              117        77     40        77      0 

src/puya/arc4_util.py

@@ -120,6 +120,7 @@ def wtype_to_arc4(wtype: wtypes.WType, loc: SourceLocation | None = None) -> str
             | wtypes.application_wtype
             | wtypes.uint64_wtype
             | wtypes.bool_wtype
+            | wtypes.string_wtype
         ):
             return wtype.name
         case wtypes.bytes_wtype:

src/puya/awst/wtypes.py

@@ -517,7 +517,7 @@ def has_arc4_equivalent_type(wtype: WType) -> bool:
     """
     Checks if a non-arc4 encoded type has an arc4 equivalent
     """
-    if wtype in (bool_wtype, uint64_wtype, bytes_wtype, biguint_wtype):
+    if wtype in (bool_wtype, uint64_wtype, bytes_wtype, biguint_wtype, string_wtype):
         return True
 
     match wtype:
@@ -535,6 +535,8 @@ def avm_to_arc4_equivalent_type(wtype: WType) -> WType:
         return ARC4UIntN.from_scale(512)
     if wtype is bytes_wtype:
         return arc4_dynamic_bytes
+    if wtype is string_wtype:
+        return arc4_string_wtype
     if isinstance(wtype, WTuple):
         return ARC4Tuple.from_types(types=[avm_to_arc4_equivalent_type(t) for t in wtype.types])
     raise InternalError(f"{wtype} does not have an arc4 equivalent type")
@@ -549,7 +551,7 @@ def arc4_to_avm_equivalent_wtype(arc4_wtype: WType) -> WType:
         case ARC4DynamicArray(element_type=ARC4UIntN(n=8)):
             return bytes_wtype
     if arc4_wtype is arc4_string_wtype:
-        return bytes_wtype
+        return bytes_wtype  # TODO: this should be string_wtype now
     elif arc4_wtype is arc4_bool_wtype:
         return bool_wtype
 

test_cases/abi_routing/contract.py

@@ -7,6 +7,7 @@
     Asset,
     Bytes,
     OnCompleteAction,
+    String,
     TransactionType,
     UInt64,
     arc4,
@@ -227,3 +228,7 @@ def method_with_more_than_15_args(
             + u.decode()
             + v.decode()
         )
+
+    @arc4.abimethod
+    def hello_with_puyapy_string(self, name: String) -> String:
+        return "Hello " + name + "!"