From cb79027f3045b979b964d5dd4e6229a6d0212b0e Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sun, 17 Sep 2023 19:23:35 +0100
Subject: Compile tuple target to stack IR

---
 .../org/shedlang/compiler/ast/typed/Typed.java     |  4 ++
 .../compiler/stackir/StackCompilerAssignTests.java | 55 ++++++++++++++++++++--
 .../stackir/instructions/InstructionMatchers.java  | 11 +++++
 3 files changed, 67 insertions(+), 3 deletions(-)

(limited to 'src/test/java')

diff --git a/src/test/java/org/shedlang/compiler/ast/typed/Typed.java b/src/test/java/org/shedlang/compiler/ast/typed/Typed.java
index 3f0230c0..0d48711c 100644
--- a/src/test/java/org/shedlang/compiler/ast/typed/Typed.java
+++ b/src/test/java/org/shedlang/compiler/ast/typed/Typed.java
@@ -186,6 +186,10 @@ public class Typed {
         return new TypedTargetNode.Reassign(name, Sources.NULL);
     }
 
+    public static TypedTargetNode targetTuple(List<TypedTargetNode> elements) {
+        return new TypedTargetNode.Tuple(elements, Sources.NULL);
+    }
+
     public static TypedTargetNode targetVal(String name) {
         return new TypedTargetNode.Val(name, Sources.NULL);
     }
diff --git a/src/test/java/org/shedlang/compiler/stackir/StackCompilerAssignTests.java b/src/test/java/org/shedlang/compiler/stackir/StackCompilerAssignTests.java
index 20abbff3..b717648a 100644
--- a/src/test/java/org/shedlang/compiler/stackir/StackCompilerAssignTests.java
+++ b/src/test/java/org/shedlang/compiler/stackir/StackCompilerAssignTests.java
@@ -3,14 +3,15 @@ package org.shedlang.compiler.stackir;
 import org.junit.jupiter.api.Test;
 import org.shedlang.compiler.ast.typed.Typed;
 
-import static org.shedlang.compiler.stackir.instructions.InstructionMatchers.isPushStringInstruction;
-import static org.shedlang.compiler.stackir.instructions.InstructionMatchers.isVarStoreInstruction;
+import java.util.List;
+
+import static org.shedlang.compiler.stackir.instructions.InstructionMatchers.*;
 import static org.zwobble.precisely.AssertThat.assertThat;
 import static org.zwobble.precisely.Matchers.isSequence;
 
 public class StackCompilerAssignTests {
     @Test
-    public void expressionIsEvaluatedAndStoredAsVar() {
+    public void whenTargetIsReassignThenExpressionIsEvaluatedAndStoredAsVar() {
         var node = Typed.assign(
             Typed.targetReassign("x"),
             Typed.stringLiteral("hello")
@@ -25,4 +26,52 @@ public class StackCompilerAssignTests {
             isVarStoreInstruction("x__0")
         ));
     }
+
+    @Test
+    public void whenTargetIsTupleThenExpressionIsDeconstructed() {
+        var node = Typed.assign(
+            Typed.targetTuple(List.of(
+                Typed.targetVal("a"),
+                Typed.targetVal("b"),
+                Typed.targetVal("c")
+            )),
+            Typed.reference("x")
+        );
+        var context = StackCompiler.Context.EMPTY
+            .addShedVariable("x")
+            .addShedVariable("a")
+            .addShedVariable("b")
+            .addShedVariable("c");
+
+        var result = StackCompiler.compileFunctionStatement(node, context);
+
+        assertThat(result.instructions(), isSequence(
+            isLocalLoadInstruction("x__0"),
+            isDuplicateInstruction(),
+            isTupleGetInstruction(0),
+            isLocalStoreInstruction("a__0"),
+            isDuplicateInstruction(),
+            isTupleGetInstruction(1),
+            isLocalStoreInstruction("b__0"),
+            isTupleGetInstruction(2),
+            isLocalStoreInstruction("c__0")
+        ));
+    }
+
+    @Test
+    public void deconstructingEmptyTupleDiscardsExpression() {
+        var node = Typed.assign(
+            Typed.targetTuple(List.of()),
+            Typed.reference("x")
+        );
+        var context = StackCompiler.Context.EMPTY
+            .addShedVariable("x");
+
+        var result = StackCompiler.compileFunctionStatement(node, context);
+
+        assertThat(result.instructions(), isSequence(
+            isLocalLoadInstruction("x__0"),
+            isDiscardInstruction()
+        ));
+    }
 }
diff --git a/src/test/java/org/shedlang/compiler/stackir/instructions/InstructionMatchers.java b/src/test/java/org/shedlang/compiler/stackir/instructions/InstructionMatchers.java
index a256c321..b50e4903 100644
--- a/src/test/java/org/shedlang/compiler/stackir/instructions/InstructionMatchers.java
+++ b/src/test/java/org/shedlang/compiler/stackir/instructions/InstructionMatchers.java
@@ -33,6 +33,10 @@ public class InstructionMatchers {
         );
     }
 
+    public static Matcher<Instruction> isDuplicateInstruction() {
+        return instanceOf(DuplicateInstruction.class);
+    }
+
     public static Matcher<Instruction> isIfInstruction(
         Matcher<Iterable<? extends Instruction>> trueBody,
         Matcher<Iterable<? extends Instruction>> falseBody
@@ -143,6 +147,13 @@ public class InstructionMatchers {
         );
     }
 
+    public static Matcher<Instruction> isTupleGetInstruction(int elementIndex) {
+        return instanceOf(
+            TupleGetInstruction.class,
+            has("elementIndex", x -> x.elementIndex(), equalTo(elementIndex))
+        );
+    }
+
     public static Matcher<Instruction> isVarLoadInstruction(String name) {
         return instanceOf(
             VarLoadInstruction.class,
-- 
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