Support non-divergent list building

2 files changed, 89 insertions, 7 deletions

diff --git a/examples/44-list-builder/shed-examples.json5 b/examples/44-list-builder/shed-examples.json5
index b669a2e6..e6cc5e44 100644
--- a/examples/44-list-builder/shed-examples.json5
+++ b/examples/44-list-builder/shed-examples.json5
@@ -3,7 +3,23 @@
     {
       project: ".",
       bin: "lists",
-      expectedOutput: "buildList()\nhello world\n\nbuildSameListTwice()\nhello world\nhello world\n",
+      expectedOutput: "\
+buildList()\n\
+hello world\n\
+\n\
+buildSameListTwice()\n\
+hello world\n\
+hello world\n\
+\n\
+buildListThenExtend()\n\
+hellohello world\n\
+\n\
+extendThenBuildPrefixAndList()\n\
+hellohello world\n\
+\n\
+buildListThenPrefix()\n\
+hello world\n\
+hello",
     },
   ],
 }
diff --git a/examples/44-list-builder/src/Lists.shed b/examples/44-list-builder/src/Lists.shed
index 7744e8d8..c6d01df5 100644
--- a/examples/44-list-builder/src/Lists.shed
+++ b/examples/44-list-builder/src/Lists.shed
@@ -3,14 +3,17 @@ import Std/Lists;
 pub fun main() ! Io -> Unit {
     buildList!();
     buildSameListTwice!();
+    buildListThenExtend!();
+    extendThenBuildPrefixAndList!();
+    buildListThenPrefix!();
 }
 
 fun buildList() ! Io -> Unit {
     print!("buildList()\n");
 
-    val builder = Lists.listBuilder[String]();
-    builder.add("hello");
-    builder.add(" world\n");
+    var builder = Lists.listBuilder[String]();
+    assign builder = builder.add("hello");
+    assign builder = builder.add(" world\n");
 
     val list = builder.build();
 
@@ -24,9 +27,9 @@ fun buildList() ! Io -> Unit {
 fun buildSameListTwice() ! Io -> Unit {
     print!("buildSameListTwice()\n");
 
-    val builder = Lists.listBuilder[String]();
-    builder.add("hello");
-    builder.add(" world\n");
+    var builder = Lists.listBuilder[String]();
+    assign builder = builder.add("hello");
+    assign builder = builder.add(" world\n");
 
     val list1 = builder.build();
     val list2 = builder.build();
@@ -41,3 +44,66 @@ fun buildSameListTwice() ! Io -> Unit {
 
     print!("\n");
 }
+
+fun buildListThenExtend() ! Io -> Unit {
+    print!("buildListThenExtend()\n");
+
+    var builder1 = Lists.listBuilder[String]();
+    assign builder1 = builder1.add("hello");
+    val list1 = builder1.build();
+
+    val builder2 = builder1.add(" world\n");
+    val list2 = builder2.build();
+
+    list1.forEach!(fn (element) ! Io {
+        print!(element);
+    });
+
+    list2.forEach!(fn (element) ! Io {
+        print!(element);
+    });
+
+    print!("\n");
+}
+
+fun extendThenBuildPrefixAndList() ! Io -> Unit {
+    print!("extendThenBuildPrefixAndList()\n");
+
+    var builder1 = Lists.listBuilder[String]();
+    assign builder1 = builder1.add("hello");
+    val builder2 = builder1.add(" world\n");
+
+    val list1 = builder1.build();
+    val list2 = builder2.build();
+
+    list1.forEach!(fn (element) ! Io {
+        print!(element);
+    });
+
+    list2.forEach!(fn (element) ! Io {
+        print!(element);
+    });
+
+    print!("\n");
+}
+
+fun buildListThenPrefix() ! Io -> Unit {
+    print!("buildListThenPrefix()\n");
+
+    var builder1 = Lists.listBuilder[String]();
+    assign builder1 = builder1.add("hello");
+    val builder2 = builder1.add(" world\n");
+
+    val list1 = builder2.build();
+    val list2 = builder1.build();
+
+    list1.forEach!(fn (element) ! Io {
+        print!(element);
+    });
+
+    list2.forEach!(fn (element) ! Io {
+        print!(element);
+    });
+
+    print!("\n");
+}