From c7b0410af60f4267264a875a80cfda2d45381bb3 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sun, 31 Jul 2016 19:33:48 +0100
Subject: Extract common code for building desugar statement transformers

---
 .../couscous/transforms/DesugarForEachToFor.java   | 11 +----------
 .../couscous/transforms/DesugarForToWhile.java     | 15 ++-------------
 .../couscous/transforms/DesugarStatement.java      | 22 ++++++++++++++++++++++
 .../couscous/transforms/DesugarSwitchToIfElse.java | 11 +----------
 4 files changed, 26 insertions(+), 33 deletions(-)
 create mode 100644 src/main/java/org/zwobble/couscous/transforms/DesugarStatement.java

diff --git a/src/main/java/org/zwobble/couscous/transforms/DesugarForEachToFor.java b/src/main/java/org/zwobble/couscous/transforms/DesugarForEachToFor.java
index bdae29a..3b95c43 100644
--- a/src/main/java/org/zwobble/couscous/transforms/DesugarForEachToFor.java
+++ b/src/main/java/org/zwobble/couscous/transforms/DesugarForEachToFor.java
@@ -8,7 +8,6 @@ import org.zwobble.couscous.types.Type;
 import org.zwobble.couscous.types.Types;
 
 import java.util.List;
-import java.util.Optional;
 
 import static org.zwobble.couscous.ast.LocalVariableDeclarationNode.localVariableDeclaration;
 import static org.zwobble.couscous.ast.MethodCallNode.methodCall;
@@ -20,15 +19,7 @@ import static org.zwobble.couscous.util.ExtraLists.list;
 public class DesugarForEachToFor {
     public static NodeTransformer transformer() {
         Scope scope = Scope.create().temporaryPrefix("_couscous_desugar_foreach_to_for");
-        return NodeTransformer.builder()
-            .transformStatement(statement -> {
-                if (statement.type() == NodeTypes.FOR_EACH) {
-                    return Optional.of(desugar(scope, ((ForEachNode) statement)));
-                } else {
-                    return Optional.empty();
-                }
-            })
-            .build();
+        return DesugarStatement.<ForEachNode>transformer(NodeTypes.FOR_EACH, node -> desugar(scope, node));
     }
 
     public static List<StatementNode> desugar(Scope scope, ForEachNode forEach) {
diff --git a/src/main/java/org/zwobble/couscous/transforms/DesugarForToWhile.java b/src/main/java/org/zwobble/couscous/transforms/DesugarForToWhile.java
index 68b961c..3bd0d32 100644
--- a/src/main/java/org/zwobble/couscous/transforms/DesugarForToWhile.java
+++ b/src/main/java/org/zwobble/couscous/transforms/DesugarForToWhile.java
@@ -7,26 +7,15 @@ import org.zwobble.couscous.ast.StatementNode;
 import org.zwobble.couscous.ast.visitors.NodeTransformer;
 
 import java.util.List;
-import java.util.Optional;
 
 import static org.zwobble.couscous.ast.ExpressionStatementNode.expressionStatement;
 import static org.zwobble.couscous.ast.WhileNode.whileLoop;
 import static org.zwobble.couscous.util.ExtraIterables.lazyMap;
-import static org.zwobble.couscous.util.ExtraLists.append;
-import static org.zwobble.couscous.util.ExtraLists.concat;
-import static org.zwobble.couscous.util.ExtraLists.list;
+import static org.zwobble.couscous.util.ExtraLists.*;
 
 public class DesugarForToWhile {
     public static NodeTransformer transformer() {
-        return NodeTransformer.builder()
-            .transformStatement(statement -> {
-                if (statement.type() == NodeTypes.FOR) {
-                    return Optional.of(desugar(((ForNode) statement)));
-                } else {
-                    return Optional.empty();
-                }
-            })
-            .build();
+        return DesugarStatement.transformer(NodeTypes.FOR, DesugarForToWhile::desugar);
     }
 
     public static List<StatementNode> desugar(ForNode forNode) {
diff --git a/src/main/java/org/zwobble/couscous/transforms/DesugarStatement.java b/src/main/java/org/zwobble/couscous/transforms/DesugarStatement.java
new file mode 100644
index 0000000..700b31b
--- /dev/null
+++ b/src/main/java/org/zwobble/couscous/transforms/DesugarStatement.java
@@ -0,0 +1,22 @@
+package org.zwobble.couscous.transforms;
+
+import org.zwobble.couscous.ast.StatementNode;
+import org.zwobble.couscous.ast.visitors.NodeTransformer;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.function.Function;
+
+class DesugarStatement {
+    static <T extends StatementNode> NodeTransformer transformer(int nodeType, Function<T, List<StatementNode>> desugar) {
+        return NodeTransformer.builder()
+            .transformStatement(statement -> {
+                if (statement.type() == nodeType) {
+                    return Optional.of(desugar.apply((T) statement));
+                } else {
+                    return Optional.empty();
+                }
+            })
+            .build();
+    }
+}
diff --git a/src/main/java/org/zwobble/couscous/transforms/DesugarSwitchToIfElse.java b/src/main/java/org/zwobble/couscous/transforms/DesugarSwitchToIfElse.java
index 5ecd25d..006a7c9 100644
--- a/src/main/java/org/zwobble/couscous/transforms/DesugarSwitchToIfElse.java
+++ b/src/main/java/org/zwobble/couscous/transforms/DesugarSwitchToIfElse.java
@@ -11,7 +11,6 @@ import org.zwobble.couscous.types.Types;
 import org.zwobble.couscous.util.ExtraLists;
 
 import java.util.List;
-import java.util.Optional;
 
 import static com.google.common.collect.Iterables.tryFind;
 import static org.zwobble.couscous.ast.IfStatementNode.ifStatement;
@@ -30,15 +29,7 @@ public class DesugarSwitchToIfElse {
 
     public static NodeTransformer transformer() {
         Scope scope = Scope.create().temporaryPrefix("_couscous_desugar_switch_to_if");
-        return NodeTransformer.builder()
-            .transformStatement(statement -> {
-                if (statement.type() == NodeTypes.SWITCH) {
-                    return Optional.of(desugar(scope, ((SwitchNode) statement)));
-                } else {
-                    return Optional.empty();
-                }
-            })
-            .build();
+        return DesugarStatement.<SwitchNode>transformer(NodeTypes.SWITCH, node -> desugar(scope, node));
     }
 
     public static List<StatementNode> desugar(Scope scope, SwitchNode switchNode) {
-- 
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