From edcaf92f6189a9f1af4978606d4948b56aca07b1 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Tue, 14 Jul 2026 22:35:53 +0100
Subject: Support mutable lets in Rust AST

---
 .../compiler/output/lang/rust/RustWriterTests.java        | 15 ++++++++++++++-
 .../output/lang/rust/ast/RustLetStatementMatcher.java     |  6 ++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

(limited to 'src/test')

diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriterTests.java b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriterTests.java
index e4cee1e..c17d96f 100644
--- a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriterTests.java
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/RustWriterTests.java
@@ -367,16 +367,29 @@ public class RustWriterTests {
     // === Let statements ===
 
     @Test
-    public void letStatementDeclaringSingleVariable() throws IOException {
+    public void letStatementDeclaringSingleImmutableVariable() throws IOException {
         var rust = RustLetStatement.arbitrary()
             .withVariableName(RustIdentifier.of("x"))
+            .withMutable(false)
             .withValue(RustBoolLiteral.arbitrary().withValue(true).build())
             .build();
 
         var string = write(writer -> writer.writeStatement(rust));
 
         assertThat(string, equalTo("let x = true;"));
+    }
+
+    @Test
+    public void letStatementDeclaringSingleMutableVariable() throws IOException {
+        var rust = RustLetStatement.arbitrary()
+            .withVariableName(RustIdentifier.of("x"))
+            .withMutable(true)
+            .withValue(RustBoolLiteral.arbitrary().withValue(true).build())
+            .build();
+
+        var string = write(writer -> writer.writeStatement(rust));
 
+        assertThat(string, equalTo("let mut x = true;"));
     }
 
     // == Expressions ==
diff --git a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustLetStatementMatcher.java b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustLetStatementMatcher.java
index c71dd98..b48d485 100644
--- a/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustLetStatementMatcher.java
+++ b/src/test/java/org/zwobble/hobgoblin/compiler/output/lang/rust/ast/RustLetStatementMatcher.java
@@ -34,6 +34,12 @@ public class RustLetStatementMatcher implements org.zwobble.precisely.Matcher<ja
         return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustLetStatementMatcher(submatchers);
     }
 
+    public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustLetStatementMatcher withMutable(org.zwobble.precisely.Matcher<? super java.lang.Boolean> mutable) {
+        var submatchers = new java.util.ArrayList<org.zwobble.precisely.Matcher<? super org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustLetStatement>>(this.submatchers);
+        submatchers.add(org.zwobble.precisely.Matchers.has("mutable", org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustLetStatement::mutable, mutable));
+        return new org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustLetStatementMatcher(submatchers);
+    }
+
     public org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustLetStatementMatcher withValue(org.zwobble.precisely.Matcher<? super org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustExpression> value) {
         var submatchers = new java.util.ArrayList<org.zwobble.precisely.Matcher<? super org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustLetStatement>>(this.submatchers);
         submatchers.add(org.zwobble.precisely.Matchers.has("value", org.zwobble.hobgoblin.compiler.output.lang.rust.ast.RustLetStatement::value, value));
-- 
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