Extract TypeSubstitutionMap.from()

2 files changed, 18 insertions, 10 deletions

diff --git a/src/main/java/org/shedlang/compiler/types/ConstructedType.java b/src/main/java/org/shedlang/compiler/types/ConstructedType.java
index b56e6a85..4a3d941e 100644
--- a/src/main/java/org/shedlang/compiler/types/ConstructedType.java
+++ b/src/main/java/org/shedlang/compiler/types/ConstructedType.java
@@ -1,6 +1,5 @@
 package org.shedlang.compiler.types;
 
-import java.util.HashMap;
 import java.util.List;
 import java.util.stream.Collectors;
 
@@ -21,14 +20,6 @@ public sealed interface ConstructedType<T extends ConstructibleType> extends Typ
     }
 
     default TypeSubstitutionMap typeSubstitutionMap() {
-        var map = new HashMap<TypeParam, Type>();
-
-        for (var argIndex = 0; argIndex < args().size(); argIndex++) {
-            var param = constructor().params().get(argIndex);
-            var arg = args().get(argIndex);
-            map.put(param, arg);
-        }
-
-        return new TypeSubstitutionMap(map);
+        return TypeSubstitutionMap.from(constructor().params(), args());
     }
 }
diff --git a/src/main/java/org/shedlang/compiler/types/TypeSubstitutionMap.java b/src/main/java/org/shedlang/compiler/types/TypeSubstitutionMap.java
index 69cc2dba..6e6bd03a 100644
--- a/src/main/java/org/shedlang/compiler/types/TypeSubstitutionMap.java
+++ b/src/main/java/org/shedlang/compiler/types/TypeSubstitutionMap.java
@@ -1,5 +1,7 @@
 package org.shedlang.compiler.types;
 
+import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 import java.util.Objects;
 
@@ -9,6 +11,21 @@ public class TypeSubstitutionMap {
         return new TypeSubstitutionMap(Map.ofEntries(map));
     }
 
+    public static TypeSubstitutionMap from(
+        List<TypeParam> params,
+        List<? extends Type> args
+    ) {
+        var map = new HashMap<TypeParam, Type>();
+
+        for (var argIndex = 0; argIndex < args.size(); argIndex++) {
+            var param = params.get(argIndex);
+            var arg = args.get(argIndex);
+            map.put(param, arg);
+        }
+
+        return new TypeSubstitutionMap(map);
+    }
+
     private final Map<TypeParam, Type> map;
 
     public TypeSubstitutionMap(Map<TypeParam, Type> map) {