Support ignore target

7 files changed, 61 insertions, 0 deletions

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 0d48711c..42a46859 100644
--- a/src/test/java/org/shedlang/compiler/ast/typed/Typed.java
+++ b/src/test/java/org/shedlang/compiler/ast/typed/Typed.java
@@ -182,6 +182,10 @@ public class Typed {
         );
     }
 
+    public static TypedTargetNode targetIgnore() {
+        return new TypedTargetNode.Ignore(Sources.NULL);
+    }
+
     public static TypedTargetNode targetReassign(String name) {
         return new TypedTargetNode.Reassign(name, Sources.NULL);
     }
diff --git a/src/test/java/org/shedlang/compiler/ast/typed/TypedNodeMatchers.java b/src/test/java/org/shedlang/compiler/ast/typed/TypedNodeMatchers.java
index c8b0501d..52d91cdf 100644
--- a/src/test/java/org/shedlang/compiler/ast/typed/TypedNodeMatchers.java
+++ b/src/test/java/org/shedlang/compiler/ast/typed/TypedNodeMatchers.java
@@ -221,6 +221,10 @@ public class TypedNodeMatchers {
         );
     }
 
+    public static Matcher<TypedTargetNode> isTypedTargetIgnore() {
+        return instanceOf(TypedTargetNode.Ignore.class);
+    }
+
     public static Matcher<TypedTargetNode> isTypedTargetReassign(String name) {
         return instanceOf(
             TypedTargetNode.Reassign.class,
diff --git a/src/test/java/org/shedlang/compiler/ast/untyped/Untyped.java b/src/test/java/org/shedlang/compiler/ast/untyped/Untyped.java
index 36668a8b..a87b1c48 100644
--- a/src/test/java/org/shedlang/compiler/ast/untyped/Untyped.java
+++ b/src/test/java/org/shedlang/compiler/ast/untyped/Untyped.java
@@ -150,6 +150,10 @@ public class Untyped {
         );
     }
 
+    public static UntypedTargetNode targetIgnore() {
+        return new UntypedTargetNode.Ignore(Sources.NULL);
+    }
+
     public static UntypedTargetNode targetReassign(String name) {
         return new UntypedTargetNode.Reassign(name, Sources.NULL);
     }
diff --git a/src/test/java/org/shedlang/compiler/ast/untyped/UntypedNodeMatchers.java b/src/test/java/org/shedlang/compiler/ast/untyped/UntypedNodeMatchers.java
index 37d432e8..7d80b4ab 100644
--- a/src/test/java/org/shedlang/compiler/ast/untyped/UntypedNodeMatchers.java
+++ b/src/test/java/org/shedlang/compiler/ast/untyped/UntypedNodeMatchers.java
@@ -190,6 +190,10 @@ public class UntypedNodeMatchers {
         return isUntypedBinaryOperationNode(UntypedBinaryOperator.SUB, left, right);
     }
 
+    public static Matcher<UntypedTargetNode> isUntypedTargetIgnoreNode() {
+        return instanceOf(UntypedTargetNode.Ignore.class);
+    }
+
     public static Matcher<UntypedTargetNode> isUntypedTargetReassignNode(String name) {
         return instanceOf(
             UntypedTargetNode.Reassign.class,
diff --git a/src/test/java/org/shedlang/compiler/parser/ParserAssignTests.java b/src/test/java/org/shedlang/compiler/parser/ParserAssignTests.java
index 9c29d328..7dc07722 100644
--- a/src/test/java/org/shedlang/compiler/parser/ParserAssignTests.java
+++ b/src/test/java/org/shedlang/compiler/parser/ParserAssignTests.java
@@ -34,4 +34,16 @@ public class ParserAssignTests {
             isUntypedReferenceNode("z")
         ));
     }
+
+    @Test
+    public void canParseIgnoreTarget() {
+        var source = "_ = x;";
+
+        var node = parseString(source, Parser::parseFunctionStatement);
+
+        assertThat(node, isUntypedAssignNode(
+            isUntypedTargetIgnoreNode(),
+            isUntypedReferenceNode("x")
+        ));
+    }
 }
diff --git a/src/test/java/org/shedlang/compiler/stackir/StackCompilerAssignTests.java b/src/test/java/org/shedlang/compiler/stackir/StackCompilerAssignTests.java
index b717648a..7c49af0a 100644
--- a/src/test/java/org/shedlang/compiler/stackir/StackCompilerAssignTests.java
+++ b/src/test/java/org/shedlang/compiler/stackir/StackCompilerAssignTests.java
@@ -11,6 +11,23 @@ import static org.zwobble.precisely.Matchers.isSequence;
 
 public class StackCompilerAssignTests {
     @Test
+    public void targetIgnoreIsCompiledToDiscard() {
+        var node = Typed.assign(
+            Typed.targetIgnore(),
+            Typed.reference("x")
+        );
+        var context = StackCompiler.Context.EMPTY
+            .addShedVariable("x");
+
+        var result = StackCompiler.compileFunctionStatement(node, context);
+
+        assertThat(result.instructions(), isSequence(
+            isLocalLoadInstruction("x__0"),
+            isDiscardInstruction()
+        ));
+    }
+
+    @Test
     public void whenTargetIsReassignThenExpressionIsEvaluatedAndStoredAsVar() {
         var node = Typed.assign(
             Typed.targetReassign("x"),
diff --git a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerAssignTests.java b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerAssignTests.java
index eb2a2db1..9bd07ffd 100644
--- a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerAssignTests.java
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerAssignTests.java
@@ -24,6 +24,22 @@ import static org.zwobble.precisely.Matchers.*;
 
 public class TypeCheckerAssignTests {
     @Test
+    public void canTypeCheckTargetIgnore() {
+        var untyped = Untyped.assign(Untyped.targetIgnore(), Untyped.stringLiteral("hello"));
+        var context = TypeCheckerContext.EMPTY
+            .enterNamespace(P.map(
+                Map.entry("x", Variable.defined(Types.STRING, VariableType.VAR))
+            ));
+
+        var typed = typeCheckFunctionStatement(untyped, context);
+
+        assertThat(typed.value(), isTypedAssignNode(
+            isTypedTargetIgnore(),
+            isTypedStringLiteralNode("hello")
+        ));
+    }
+
+    @Test
     public void canTypeCheckReassign() {
         var untyped = Untyped.assign(Untyped.targetReassign("x"), Untyped.stringLiteral("hello"));
         var context = TypeCheckerContext.EMPTY