Introduce ShidBlock

17 files changed, 156 insertions, 118 deletions

diff --git a/src/test/java/org/shedlang/compiler/patio/PatioCodeGenDefineFunctionTests.java b/src/test/java/org/shedlang/compiler/patio/PatioCodeGenDefineFunctionTests.java
index 3fd914be..9c52db77 100644
--- a/src/test/java/org/shedlang/compiler/patio/PatioCodeGenDefineFunctionTests.java
+++ b/src/test/java/org/shedlang/compiler/patio/PatioCodeGenDefineFunctionTests.java
@@ -25,10 +25,10 @@ public class PatioCodeGenDefineFunctionTests {
             List.of(),
             List.of(),
             FreeVariables.empty(),
-            List.of(
+            Shid.block(List.of(
                 Shid.pushUnit(),
                 Shid.return_()
-            ),
+            )),
             ShidDefineFunction.Variant.FUNCTION,
             Sources.NULL
         );
@@ -46,10 +46,10 @@ public class PatioCodeGenDefineFunctionTests {
             List.of(),
             List.of(),
             FreeVariables.builder().plus("a", Sources.NULL).plus("b", Sources.NULL).build(),
-            List.of(
+            Shid.block(List.of(
                 Shid.localLoad("a"),
                 Shid.return_()
-            ),
+            )),
             ShidDefineFunction.Variant.FUNCTION,
             Sources.NULL
         );
@@ -69,10 +69,10 @@ public class PatioCodeGenDefineFunctionTests {
             List.of(),
             List.of(),
             FreeVariables.builder().plus("a", Sources.NULL).plus("b", Sources.NULL).build(),
-            List.of(
+            Shid.block(List.of(
                 Shid.localLoad("a"),
                 Shid.return_()
-            ),
+            )),
             ShidDefineFunction.Variant.FUNCTION,
             Sources.NULL
         );
@@ -104,10 +104,10 @@ public class PatioCodeGenDefineFunctionTests {
                 .plus("a", Sources.NULL)
                 .plus("b", Sources.NULL)
                 .build(),
-            List.of(
+            Shid.block(List.of(
                 Shid.localLoad("a"),
                 Shid.return_()
-            ),
+            )),
             ShidDefineFunction.Variant.FUNCTION,
             Sources.NULL
         );
@@ -130,14 +130,14 @@ public class PatioCodeGenDefineFunctionTests {
             // Define named params in non-lexical order
             List.of(Shid.param("paramB"), Shid.param("paramC"), Shid.param("paramA")),
             FreeVariables.builder().plus("a", Sources.NULL).plus("b", Sources.NULL).build(),
-            List.of(
+            Shid.block(List.of(
                 Shid.localLoad("a"),
                 Shid.localLoad("param1"),
                 Shid.intAdd(),
                 Shid.localLoad("paramA"),
                 Shid.intAdd(),
                 Shid.return_()
-            ),
+            )),
             ShidDefineFunction.Variant.FUNCTION,
             Sources.NULL
         );
@@ -157,10 +157,10 @@ public class PatioCodeGenDefineFunctionTests {
             List.of(),
             List.of(),
             FreeVariables.empty(),
-            List.of(
+            Shid.block(List.of(
                 Shid.pushUnit(),
                 Shid.resume()
-            ),
+            )),
             ShidDefineFunction.Variant.EFFECT_HANDLER_METHOD,
             Sources.NULL
         );
diff --git a/src/test/java/org/shedlang/compiler/patio/PatioCodeGenIfTests.java b/src/test/java/org/shedlang/compiler/patio/PatioCodeGenIfTests.java
index 34edd733..9a385a1f 100644
--- a/src/test/java/org/shedlang/compiler/patio/PatioCodeGenIfTests.java
+++ b/src/test/java/org/shedlang/compiler/patio/PatioCodeGenIfTests.java
@@ -18,14 +18,14 @@ public class PatioCodeGenIfTests {
     public void canGenerateCodeForIfWithNoResults(Snapshotter snapshotter) throws IOException {
         var instruction = Shid.if_(
             0,
-            List.of(
+            Shid.block(List.of(
                 Shid.pushInt(1),
                 Shid.discard()
-            ),
-            List.of(
+            )),
+            Shid.block(List.of(
                 Shid.pushInt(101),
                 Shid.discard()
-            )
+            ))
         );
         var context = PatioCodeGenContext.EMPTY
             .temporaryPush(new PatioLocalRef("other"))
@@ -40,16 +40,16 @@ public class PatioCodeGenIfTests {
     public void canGenerateCodeForIfWithSingleResult(Snapshotter snapshotter) throws IOException {
         var instruction = Shid.if_(
             1,
-            List.of(
+            Shid.block(List.of(
                 Shid.pushInt(1),
                 Shid.pushInt(2),
                 Shid.intAdd()
-            ),
-            List.of(
+            )),
+            Shid.block(List.of(
                 Shid.pushInt(101),
                 Shid.pushInt(102),
                 Shid.intAdd()
-            )
+            ))
         );
         var context = PatioCodeGenContext.EMPTY
             .temporaryPush(new PatioLocalRef("other"))
@@ -64,14 +64,14 @@ public class PatioCodeGenIfTests {
     public void canGenerateCodeForIfWithMultipleResults(Snapshotter snapshotter) throws IOException {
         var instruction = Shid.if_(
             2,
-            List.of(
+            Shid.block(List.of(
                 Shid.pushInt(1),
                 Shid.pushInt(2)
-            ),
-            List.of(
+            )),
+            Shid.block(List.of(
                 Shid.pushInt(101),
                 Shid.pushInt(102)
-            )
+            ))
         );
         var context = PatioCodeGenContext.EMPTY
             .temporaryPush(new PatioLocalRef("other"))
diff --git a/src/test/java/org/shedlang/compiler/patio/PatioCodeGenLoopTests.java b/src/test/java/org/shedlang/compiler/patio/PatioCodeGenLoopTests.java
index 6a9648db..67ab77b5 100644
--- a/src/test/java/org/shedlang/compiler/patio/PatioCodeGenLoopTests.java
+++ b/src/test/java/org/shedlang/compiler/patio/PatioCodeGenLoopTests.java
@@ -16,10 +16,10 @@ public class PatioCodeGenLoopTests {
     @Test
     public void canGenerateCodeForLoop(Snapshotter snapshotter) throws IOException {
         var instruction = Shid.loop(
-            List.of(
+            Shid.block(List.of(
                 Shid.pushInt(1),
                 Shid.discard()
-            )
+            ))
         );
         var context = PatioCodeGenContext.EMPTY;
 
diff --git a/src/test/java/org/shedlang/compiler/patio/PatioCodeGenNamespaceTests.java b/src/test/java/org/shedlang/compiler/patio/PatioCodeGenNamespaceTests.java
index c7dcf094..057f56e5 100644
--- a/src/test/java/org/shedlang/compiler/patio/PatioCodeGenNamespaceTests.java
+++ b/src/test/java/org/shedlang/compiler/patio/PatioCodeGenNamespaceTests.java
@@ -3,11 +3,10 @@ package org.shedlang.compiler.patio;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.shedlang.compiler.ast.typed.FreeVariables;
-import org.shedlang.compiler.sources.Sources;
 import org.shedlang.compiler.shid.ShidNamespace;
-import org.shedlang.compiler.shid.instructions.ShidDefineFunction;
-import org.shedlang.compiler.shid.instructions.ShidInstruction;
 import org.shedlang.compiler.shid.instructions.Shid;
+import org.shedlang.compiler.shid.instructions.ShidDefineFunction;
+import org.shedlang.compiler.sources.Sources;
 import org.shedlang.compiler.testing.snapshots.SnapshotResolver;
 import org.shedlang.compiler.testing.snapshots.Snapshotter;
 import org.shedlang.compiler.typechecker.TypeInfos;
@@ -29,14 +28,14 @@ public class PatioCodeGenNamespaceTests {
             List.of(),
             List.of(),
             FreeVariables.empty(),
-            List.of(
+            Shid.block(List.of(
                 Shid.pushUnit(),
                 Shid.return_()
-            ),
+            )),
             ShidDefineFunction.Variant.FUNCTION,
             Sources.NULL
         );
-        var instructions = List.<ShidInstruction>of(instruction);
+        var instructions = Shid.block(List.of(instruction));
         var namespaceName = NamespaceName.of("An","Example");
         var typeInfos = TypeInfos.EMPTY
             .addNamespaceTypeInfo(
diff --git a/src/test/java/org/shedlang/compiler/patio/PatioCodeGenSwitchTests.java b/src/test/java/org/shedlang/compiler/patio/PatioCodeGenSwitchTests.java
index 58463cb4..e9838702 100644
--- a/src/test/java/org/shedlang/compiler/patio/PatioCodeGenSwitchTests.java
+++ b/src/test/java/org/shedlang/compiler/patio/PatioCodeGenSwitchTests.java
@@ -27,19 +27,19 @@ public class PatioCodeGenSwitchTests {
             List.of(
                 Shid.switchCase(
                     structType1,
-                    List.of(
+                    Shid.block(List.of(
                         Shid.pushInt(1),
                         Shid.pushInt(2),
                         Shid.intAdd()
-                    )
+                    ))
                 ),
                 Shid.switchCase(
                     structType2,
-                    List.of(
+                    Shid.block(List.of(
                         Shid.pushInt(101),
                         Shid.pushInt(102),
                         Shid.intAdd()
-                    )
+                    ))
                 )
             )
         );
diff --git a/src/test/java/org/shedlang/compiler/patio/PatioCodeGenTryTests.java b/src/test/java/org/shedlang/compiler/patio/PatioCodeGenTryTests.java
index f534534c..a0f71ed4 100644
--- a/src/test/java/org/shedlang/compiler/patio/PatioCodeGenTryTests.java
+++ b/src/test/java/org/shedlang/compiler/patio/PatioCodeGenTryTests.java
@@ -23,9 +23,9 @@ public class PatioCodeGenTryTests {
         var shidInstruction = Shid.try_(
             effect,
             List.of("a", "c", "b"),
-            List.of(
+            Shid.block(List.of(
                 Shid.pushInt(42)
-            )
+            ))
         );
         var typeInfos = TypeCheckerContext.EMPTY
             .addUserDefinedEffectInfo(
diff --git a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenFunctionDefinitionTests.java b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenFunctionDefinitionTests.java
index 0f6a3835..e0c63896 100644
--- a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenFunctionDefinitionTests.java
+++ b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenFunctionDefinitionTests.java
@@ -39,12 +39,12 @@ public class ShidCodeGenFunctionDefinitionTests {
                 has("freeVariables", x -> x.freeVariables(), containsExactly(
                     has("name", x -> x.name(), equalTo("z__0"))
                 )),
-                has("body", x -> x.body(), isSequence(
+                has("body", x -> x.body(), isBlockInstruction(isSequence(
                     isPushStringInstruction("hello"),
                     isDiscardInstruction(),
                     isPushUnitInstruction(),
                     isReturnInstruction()
-                ))
+                )))
             ),
             isLocalStoreInstruction("f__0")
         ));
@@ -64,10 +64,10 @@ public class ShidCodeGenFunctionDefinitionTests {
         assertThat(result.instructions(), isSequence(
             instanceOf(
                 ShidDefineFunction.class,
-                has("body", x -> x.body(), isSequence(
+                has("body", x -> x.body(), isBlockInstruction(isSequence(
                     isPushStringInstruction("hello"),
                     isReturnInstruction()
-                ))
+                )))
             ),
             isLocalStoreInstruction("f__0")
         ));
diff --git a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenFunctionExpressionTests.java b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenFunctionExpressionTests.java
index c5f78340..2783a389 100644
--- a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenFunctionExpressionTests.java
+++ b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenFunctionExpressionTests.java
@@ -38,12 +38,12 @@ public class ShidCodeGenFunctionExpressionTests {
                 has("freeVariables", x -> x.freeVariables(), containsExactly(
                     has("name", x -> x.name(), equalTo("z__0"))
                 )),
-                has("body", x -> x.body(), isSequence(
+                has("body", x -> x.body(), isBlockInstruction(isSequence(
                     isPushStringInstruction("hello"),
                     isDiscardInstruction(),
                     isPushUnitInstruction(),
                     isReturnInstruction()
-                ))
+                )))
             )
         ));
     }
@@ -61,10 +61,10 @@ public class ShidCodeGenFunctionExpressionTests {
         assertThat(result.instructions(), isSequence(
             instanceOf(
                 ShidDefineFunction.class,
-                has("body", x -> x.body(), isSequence(
+                has("body", x -> x.body(), isBlockInstruction(isSequence(
                     isPushStringInstruction("hello"),
                     isReturnInstruction()
-                ))
+                )))
             )
         ));
     }
diff --git a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenIfTests.java b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenIfTests.java
index f1f81e95..df07214d 100644
--- a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenIfTests.java
+++ b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenIfTests.java
@@ -35,13 +35,15 @@ public class ShidCodeGenIfTests {
         assertThat(result.instructions(), isSequence(
             isLocalLoadInstruction("c__0"),
             isIfInstruction(
-                isSequence(
+                isBlockInstruction(isSequence(
                     isPushIntInstruction(42)
-                ),
-                isSequence(
-                    isPushStringInstruction("x"),
-                    isReturnInstruction()
-                )
+                )),
+                isBlockInstruction(isSequence(
+                    isBlockInstruction(isSequence(
+                        isPushStringInstruction("x"),
+                        isReturnInstruction()
+                    ))
+                ))
             )
         ));
     }
@@ -77,21 +79,23 @@ public class ShidCodeGenIfTests {
         assertThat(result.instructions(), isSequence(
             isLocalLoadInstruction("c__0"),
             isIfInstruction(
-                isSequence(
+                isBlockInstruction(isSequence(
                     isPushIntInstruction(42)
-                ),
-                isSequence(
+                )),
+                isBlockInstruction(isSequence(
                     isLocalLoadInstruction("d__0"),
                     isIfInstruction(
-                        isSequence(
+                        isBlockInstruction(isSequence(
                             isPushIntInstruction(1)
-                        ),
-                        isSequence(
-                            isPushStringInstruction("x"),
-                            isReturnInstruction()
-                        )
+                        )),
+                        isBlockInstruction(isSequence(
+                            isBlockInstruction(isSequence(
+                                isPushStringInstruction("x"),
+                                isReturnInstruction()
+                            ))
+                        ))
                     )
-                )
+                ))
             )
         ));
     }
diff --git a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenNamespaceTests.java b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenNamespaceTests.java
index f56ba972..af0bae77 100644
--- a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenNamespaceTests.java
+++ b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenNamespaceTests.java
@@ -33,7 +33,7 @@ public class ShidCodeGenNamespaceTests {
 
         var shidNamespace = ShidCodeGen.compileNamespace(node);
 
-        assertThat(shidNamespace.instructions(), isSequence(
+        assertThat(shidNamespace.body(), isBlockInstruction(isSequence(
             // TODO: test the builtin loading properly
             instanceOf(ShidNamespaceImport.class),
             instanceOf(ShidFieldLoad.class),
@@ -46,7 +46,7 @@ public class ShidCodeGenNamespaceTests {
             isLocalStoreInstruction("f__0"),
             isLocalLoadInstruction("f__0"),
             isNamespaceFieldStoreInstruction(namespaceName, "f")
-        ));
+        )));
     }
 
     @Test
@@ -60,7 +60,7 @@ public class ShidCodeGenNamespaceTests {
 
         var shidNamespace = ShidCodeGen.compileNamespace(node);
 
-        assertThat(shidNamespace.instructions(), isSequence(
+        assertThat(shidNamespace.body(), isBlockInstruction(isSequence(
             // TODO: test the builtin loading properly
             instanceOf(ShidNamespaceImport.class),
             instanceOf(ShidFieldLoad.class),
@@ -70,7 +70,7 @@ public class ShidCodeGenNamespaceTests {
             isLocalStoreInstruction("A__0"),
             isNamespaceImportInstruction(NamespaceName.of("B")),
             isLocalStoreInstruction("B__0")
-        ));
+        )));
     }
 
     @Test
@@ -93,7 +93,7 @@ public class ShidCodeGenNamespaceTests {
 
         var shidNamespace = ShidCodeGen.compileNamespace(node);
 
-        assertThat(shidNamespace.instructions(), isSequence(
+        assertThat(shidNamespace.body(), isBlockInstruction(isSequence(
             // TODO: test the builtin loading properly
             instanceOf(ShidNamespaceImport.class),
             instanceOf(ShidFieldLoad.class),
@@ -113,6 +113,6 @@ public class ShidCodeGenNamespaceTests {
             isNamespaceFieldStoreInstruction(namespaceName, "f"),
             isLocalLoadInstruction("None__0"),
             isNamespaceFieldStoreInstruction(namespaceName, "None")
-        ));
+        )));
     }
 }
diff --git a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenTryTests.java b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenTryTests.java
index daff19b0..ddcf1d08 100644
--- a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenTryTests.java
+++ b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenTryTests.java
@@ -9,6 +9,7 @@ import org.shedlang.compiler.shid.instructions.ShidTry;
 import org.shedlang.compiler.types.Effects;
 import org.shedlang.compiler.types.NamespaceName;
 
+import static org.shedlang.compiler.shid.instructions.InstructionMatchers.isBlockInstruction;
 import static org.shedlang.compiler.shid.instructions.InstructionMatchers.isPushIntInstruction;
 import static org.zwobble.precisely.AssertThat.assertThat;
 import static org.zwobble.precisely.Matchers.*;
@@ -54,9 +55,9 @@ public class ShidCodeGenTryTests {
                     equalTo("read"),
                     equalTo("write")
                 )),
-                has("body", x -> x.body(), isSequence(
+                has("body", x -> x.body(), isBlockInstruction(isSequence(
                     isPushIntInstruction(42)
-                ))
+                )))
             )
         ));
     }
diff --git a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenValTests.java b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenValTests.java
index 5007e1e8..45f29904 100644
--- a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenValTests.java
+++ b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenValTests.java
@@ -83,20 +83,22 @@ public class ShidCodeGenValTests {
             isDiscardInstruction(),
             isPushBoolInstruction(true),
             isIfInstruction(
-                isSequence(
+                isBlockInstruction(isSequence(
                     isPushIntInstruction(11),
                     isLocalStoreInstruction("x__1"),
                     isLocalLoadInstruction("x__1"),
                     isDiscardInstruction(),
                     isPushUnitInstruction()
-                ),
-                isSequence(
-                    isPushIntInstruction(12),
-                    isLocalStoreInstruction("x__2"),
-                    isLocalLoadInstruction("x__2"),
-                    isDiscardInstruction(),
-                    isPushUnitInstruction()
-                )
+                )),
+                isBlockInstruction(isSequence(
+                    isBlockInstruction(isSequence(
+                        isPushIntInstruction(12),
+                        isLocalStoreInstruction("x__2"),
+                        isLocalLoadInstruction("x__2"),
+                        isDiscardInstruction(),
+                        isPushUnitInstruction()
+                    ))
+                ))
             ),
             isDiscardInstruction(),
             isLocalLoadInstruction("x__0"),
diff --git a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenWhenTests.java b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenWhenTests.java
index f3e2880c..a7abfc69 100644
--- a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenWhenTests.java
+++ b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenWhenTests.java
@@ -45,15 +45,15 @@ public class ShidCodeGenWhenTests {
                 isSequence(
                     isSwitchInstructionCase(
                         Types.struct(NAMESPACE_NAME, "A"),
-                        isSequence(
+                        isBlockInstruction(isSequence(
                             isPushStringInstruction("a")
-                        )
+                        ))
                     ),
                     isSwitchInstructionCase(
                         Types.struct(NAMESPACE_NAME, "B"),
-                        isSequence(
+                        isBlockInstruction(isSequence(
                             isPushStringInstruction("b")
-                        )
+                        ))
                     )
                 )
             )
diff --git a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenWhileTests.java b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenWhileTests.java
index 1ab5240a..3307db91 100644
--- a/src/test/java/org/shedlang/compiler/shid/ShidCodeGenWhileTests.java
+++ b/src/test/java/org/shedlang/compiler/shid/ShidCodeGenWhileTests.java
@@ -25,18 +25,20 @@ public class ShidCodeGenWhileTests {
 
         assertThat(result.instructions(), isSequence(
             isLoopInstruction(
-                isSequence(
+                isBlockInstruction(isSequence(
                     isLocalLoadInstruction("c__0"),
                     isIfInstruction(
-                        isSequence(),
-                        isSequence(
+                        isBlockInstruction(isSequence()),
+                        isBlockInstruction(isSequence(
                             isLoopBreakInstruction()
-                        )
+                        ))
                     ),
-                    isPushIntInstruction(42),
-                    isDiscardInstruction(),
+                    isBlockInstruction(isSequence(
+                        isPushIntInstruction(42),
+                        isDiscardInstruction()
+                    )),
                     isLoopContinueInstruction()
-                )
+                ))
             )
         ));
     }
@@ -58,18 +60,20 @@ public class ShidCodeGenWhileTests {
 
         assertThat(result.instructions(), isSequence(
             isLoopInstruction(
-                isSequence(
+                isBlockInstruction(isSequence(
                     isLocalLoadInstruction("c__0"),
                     isIfInstruction(
-                        isSequence(),
-                        isSequence(
+                        isBlockInstruction(isSequence()),
+                        isBlockInstruction(isSequence(
                             isLoopBreakInstruction()
-                        )
+                        ))
                     ),
-                    isPushIntInstruction(42),
-                    isDiscardInstruction(),
+                    isBlockInstruction(isSequence(
+                        isPushIntInstruction(42),
+                        isDiscardInstruction()
+                    )),
                     isLoopContinueInstruction()
-                )
+                ))
             )
         ));
     }
diff --git a/src/test/java/org/shedlang/compiler/shid/ShidSerializerTests.java b/src/test/java/org/shedlang/compiler/shid/ShidSerializerTests.java
index 62346f3b..0076b982 100644
--- a/src/test/java/org/shedlang/compiler/shid/ShidSerializerTests.java
+++ b/src/test/java/org/shedlang/compiler/shid/ShidSerializerTests.java
@@ -15,6 +15,21 @@ import static org.zwobble.precisely.Matchers.equalTo;
 
 public class ShidSerializerTests {
     @Test
+    public void canSerializeBlock() {
+        var instruction = Shid.block(List.of(Shid.pushInt(1)));
+
+        var string = serialize(instruction);
+
+        assertThat(string, equalTo("""
+            (
+                block
+                (
+                    (push-int 1)
+                )
+            )"""));
+    }
+
+    @Test
     public void canSerializeCall() {
         var instruction = Shid.call(1, List.of("x", "y"));
 
@@ -156,14 +171,14 @@ public class ShidSerializerTests {
     public void canSerializeIf() {
         var instruction = Shid.if_(
             1,
-            List.of(
+            Shid.block(List.of(
                 Shid.pushUnit()
-            ),
-            List.of(
+            )),
+            Shid.block(List.of(
                 Shid.localLoad("x"),
                 Shid.discard(),
                 Shid.pushBool(true)
-            )
+            ))
         );
 
         var string = serialize(instruction);
@@ -249,10 +264,10 @@ public class ShidSerializerTests {
     @Test
     public void canSerializeLoop() {
         var instruction = Shid.loop(
-            List.of(
+            Shid.block(List.of(
                 Shid.localLoad("x"),
                 Shid.discard()
-            )
+            ))
         );
 
         var string = serialize(instruction);
@@ -385,15 +400,15 @@ public class ShidSerializerTests {
         var instruction = Shid.switch_(List.of(
             Shid.switchCase(
                 Types.struct(NamespaceName.of("Example", "Project"), "A"),
-                List.of(
+                Shid.block(List.of(
                     Shid.return_()
-                )
+                ))
             ),
             Shid.switchCase(
                 Types.struct(NamespaceName.of("Example", "Project"), "B"),
-                List.of(
+                Shid.block(List.of(
                     Shid.discard()
-                )
+                ))
             )
         ));
 
@@ -425,9 +440,9 @@ public class ShidSerializerTests {
         var instruction = Shid.try_(
             effect,
             List.of("read", "write"),
-            List.of(
+            Shid.block(List.of(
                 Shid.pushUnit()
-            )
+            ))
         );
 
         var string = serialize(instruction);
diff --git a/src/test/java/org/shedlang/compiler/shid/instructions/InstructionMatchers.java b/src/test/java/org/shedlang/compiler/shid/instructions/InstructionMatchers.java
index ed7b1e83..6e57a4b2 100644
--- a/src/test/java/org/shedlang/compiler/shid/instructions/InstructionMatchers.java
+++ b/src/test/java/org/shedlang/compiler/shid/instructions/InstructionMatchers.java
@@ -14,6 +14,15 @@ public class InstructionMatchers {
     private InstructionMatchers() {
     }
 
+    public static Matcher<ShidInstruction> isBlockInstruction(
+        Matcher<Iterable<? extends ShidInstruction>> instructions
+    ) {
+        return instanceOf(
+            ShidBlock.class,
+            has("instructions", x -> x.instructions(), instructions)
+        );
+    }
+
     public static Matcher<ShidInstruction> isBreakInstruction(UserDefinedEffect effect) {
         return instanceOf(
             ShedEffectHandlerBreak.class,
@@ -68,8 +77,8 @@ public class InstructionMatchers {
     }
 
     public static Matcher<ShidInstruction> isIfInstruction(
-        Matcher<Iterable<? extends ShidInstruction>> trueBody,
-        Matcher<Iterable<? extends ShidInstruction>> falseBody
+        Matcher<? super ShidBlock> trueBody,
+        Matcher<? super ShidBlock> falseBody
     ) {
         return instanceOf(
             ShidIf.class,
@@ -109,7 +118,7 @@ public class InstructionMatchers {
     }
 
     public static Matcher<ShidInstruction> isLoopInstruction(
-        Matcher<Iterable<? extends ShidInstruction>> body
+        Matcher<? super ShidBlock> body
     ) {
         return instanceOf(
             ShidLoop.class,
@@ -199,7 +208,7 @@ public class InstructionMatchers {
 
     public static Matcher<ShidSwitch.Case> isSwitchInstructionCase(
         StructType caseType,
-        Matcher<Iterable<? extends ShidInstruction>> body
+        Matcher<? super ShidBlock> body
     ) {
         return allOf(
             has("caseType", x -> x.caseType(), equalTo(caseType)),
diff --git a/src/test/java/org/shedlang/compiler/shid/instructions/Shid.java b/src/test/java/org/shedlang/compiler/shid/instructions/Shid.java
index a30b806b..f3ba5614 100644
--- a/src/test/java/org/shedlang/compiler/shid/instructions/Shid.java
+++ b/src/test/java/org/shedlang/compiler/shid/instructions/Shid.java
@@ -12,6 +12,10 @@ public class Shid {
     private Shid() {
     }
 
+    public static ShidBlock block(List<ShidInstruction> instructions) {
+        return new ShidBlock(instructions, Sources.NULL);
+    }
+
     public static ShidInstruction call(int positionalArgCount, List<String> namedArgNames) {
         return new ShidCall(positionalArgCount, namedArgNames, Sources.NULL);
     }
@@ -73,8 +77,8 @@ public class Shid {
 
     public static ShidInstruction if_(
         int resultCount,
-        List<ShidInstruction> trueBody,
-        List<ShidInstruction> falseBody
+        ShidBlock trueBody,
+        ShidBlock falseBody
     ) {
         return new ShidIf(resultCount, trueBody, falseBody, Sources.NULL);
     }
@@ -107,7 +111,7 @@ public class Shid {
         return new ShidLocalStore(name, Sources.NULL);
     }
 
-    public static ShidInstruction loop(List<ShidInstruction> body) {
+    public static ShidInstruction loop(ShidBlock body) {
         return new ShidLoop(body, Sources.NULL);
     }
 
@@ -165,7 +169,7 @@ public class Shid {
 
     public static ShidSwitch.Case switchCase(
         StructType type,
-        List<ShidInstruction> body
+        ShidBlock body
     ) {
         return new ShidSwitch.Case(type, body, Sources.NULL);
     }
@@ -173,7 +177,7 @@ public class Shid {
     public static ShidInstruction try_(
         UserDefinedEffect handledEffect,
         List<String> handlerMethodNames,
-        List<ShidInstruction> body
+        ShidBlock body
     ) {
         return new ShidTry(
             handledEffect,