fixes #7222; fixes #5595; fixes #3747

* late instantiation for the generic procs' default param values
* automatic mixin behaviour in concepts

Other fixes:

* don't render the automatically inserted default params in calls
* better rendering of tyFromExpr

tests/concepts/libs/trie.nim

@@ -0,0 +1,26 @@
+import
+  hashes, tables, trie_database
+
+type
+  MemDBTable = Table[KeccakHash, string]
+
+  MemDB* = object
+    tbl: MemDBTable
+
+proc hash*(key: KeccakHash): int =
+  hashes.hash(key.data)
+
+proc get*(db: MemDB, key: KeccakHash): string =
+  db.tbl[key]
+
+proc del*(db: var MemDB, key: KeccakHash): bool =
+  if db.tbl.hasKey(key):
+    db.tbl.del(key)
+    return true
+  else:
+    return false
+
+proc put*(db: var MemDB, key: KeccakHash, value: string): bool =
+  db.tbl[key] = value
+  return true
+

tests/concepts/libs/trie_database.nim

@@ -0,0 +1,12 @@
+type
+  KeccakHash* = object
+    data*: string
+
+  BytesRange* = object
+    bytes*: string
+
+  TrieDatabase* = concept db
+    put(var db, KeccakHash, string) is bool
+    del(var db, KeccakHash) is bool
+    get(db, KeccakHash) is string
+

tests/concepts/ttrieconcept.nim

@@ -0,0 +1,7 @@
+import libs/[trie_database, trie]
+
+proc takeDb(d: TrieDatabase) = discard
+var mdb: MemDB
+
+takeDb(mdb)
+