core/types: improve error for too short transaction / receipt encoding

[Juicestus]

Because the switch statement checks for EIP-2718 (String and Bytes) and legacy (List) transactions, the default should throw an error expecting the newer String and Bytes rather than the List. Changed return rlp.ErrExpectedList to return rlp.ErrExpectedString in the default cases.

closes #24227

[fjl]

I think this issue is being extremely picky. The only case where this error will happen is when trying to decode the transaction from a single byte, i.e. input 0x01. We could just work around this by removing the default: completely and always attempt to parse as a typed tx.

[holiman]

LGTM

[holiman]

Needs this fix

diff --git a/cmd/evm/testdata/15/exp3.json b/cmd/evm/testdata/15/exp3.json
index 6c46d267cf..b5a6c3324d 100644
--- a/cmd/evm/testdata/15/exp3.json
+++ b/cmd/evm/testdata/15/exp3.json
@@ -21,19 +21,19 @@
     "error": "transaction type not supported"
   },
   {
-    "error": "rlp: expected List"
+    "error": "transaction type not supported"
   },
   {
-    "error": "rlp: expected List"
+    "error": "EOF"
   },
   {
-    "error": "rlp: expected List"
+    "error": "EOF"
   },
   {
-    "error": "rlp: expected List"
+    "error": "EOF"
   },
   {
-    "error": "rlp: expected List"
+    "error": "transaction type not supported"
   },
   {
     "error": "rlp: expected input list for types.AccessListTx"

[fjl]

I don't want to merge this as-is because returning io.EOF as an error is not good. I will improve the error.

[fjl]

Actually, this uncovered that rlp.DecodeBytes returns io.EOF for empty input. I don't dare change that right now, but it's wrong. It should return io.ErrUnexpectedEOF instead.