Add amalgamation

src/core/contingency-core.scala

@@ -103,7 +103,13 @@ def attempt[ErrorType <: Exception](using DummyImplicit)[SuccessType]
         : Attempt[SuccessType, ErrorType] =
 
   boundary: label ?=>
-    Attempt.Success(block(using AttemptTactic[ErrorType, SuccessType](label)))
+    Attempt.Success(block(using AttemptTactic(label)))
+
+def amalgamate[ErrorType <: Exception](using DummyImplicit)[SuccessType]
+    (block: AmalgamateTactic[ErrorType, SuccessType] ?=> SuccessType)
+        : SuccessType | ErrorType =
+  boundary: label ?=>
+    block(using AmalgamateTactic(label))
 
 def abandonment[ErrorType <: Error](using Quotes, Realm)[SuccessType]
     (block: AbandonTactic[ErrorType, SuccessType] ?=> SuccessType)

src/core/contingency.AmalgamateTactic.scala

@@ -0,0 +1,31 @@
+/*
+    Contingency, version [unreleased]. Copyright 2024 Jon Pretty, Propensive OÜ.
+
+    The primary distribution site is: https://propensive.com/
+
+    Licensed under the Apache License, Version 2.0 (the "License"); you may not use this
+    file except in compliance with the License. You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing, software distributed under the
+    License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
+    either express or implied. See the License for the specific language governing permissions
+    and limitations under the License.
+*/
+
+package contingency
+
+import language.experimental.pureFunctions
+
+import rudiments.*
+
+@capability
+class AmalgamateTactic[ErrorType <: Exception, SuccessType]
+    (label: boundary.Label[SuccessType | ErrorType])
+extends Tactic[ErrorType]:
+  type Result = SuccessType | ErrorType
+  type Return = SuccessType | ErrorType
+
+  def record(error: ErrorType): Unit = boundary.break(error)(using label)
+  def abort(error: ErrorType): Nothing = boundary.break(error)(using label)

src/test/contingency.Tests.scala

@@ -125,4 +125,14 @@ object Tests extends Suite(t"Contingency tests"):
         abort(BetaError())
         "success"
 
-    .assert(_ == "beta")
+    test(t"amalgamation failure"):
+      amalgamate:
+        abort(BetaError())
+        42
+    .assert(_ == BetaError())
+
+    test(t"amalgamation success"):
+      amalgamate:
+        if false then abort(BetaError())
+        42
+    .assert(_ == 42)