From a0d962a3609abee2148abcffe54fae9b09663830 Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Sat, 8 Jul 2023 12:17:47 +0100
Subject: Type-check string addition

---
 .../org/shedlang/compiler/ast/typed/TypedNodeMatchers.java  |  7 +++++++
 .../typechecker/TypeCheckerBinaryOperationTests.java        | 13 +++++++++++++
 2 files changed, 20 insertions(+)

(limited to 'src/test/java')

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 9b432d5e..d32e0d23 100644
--- a/src/test/java/org/shedlang/compiler/ast/typed/TypedNodeMatchers.java
+++ b/src/test/java/org/shedlang/compiler/ast/typed/TypedNodeMatchers.java
@@ -153,6 +153,13 @@ public class TypedNodeMatchers {
         );
     }
 
+    public static Matcher<TypedExpressionNode> isTypedStringAddNode(
+        Matcher<TypedExpressionNode> left,
+        Matcher<TypedExpressionNode> right
+    ) {
+        return isTypedBinaryOperationNode(TypedBinaryOperator.STRING_ADD, left, right);
+    }
+
     public static Matcher<TypedExpressionNode> isTypedStringLiteralNode(String value) {
         return instanceOf(
             TypedStringLiteralNode.class,
diff --git a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerBinaryOperationTests.java b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerBinaryOperationTests.java
index e7721d1d..0a07f682 100644
--- a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerBinaryOperationTests.java
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerBinaryOperationTests.java
@@ -92,4 +92,17 @@ public class TypeCheckerBinaryOperationTests {
         assertThat(error.left(), equalTo(Types.INT));
         assertThat(error.right(), equalTo(Types.STRING));
     }
+
+    @Test
+    public void whenBothOperandsAreStringAndOperatorIsAddThenIsTypedAsStringAdd() {
+        var untyped = Untyped.add(Untyped.stringLiteral("a"), Untyped.stringLiteral("b"));
+
+        var typed = TypeChecker.typeCheckExpression(untyped, TypeCheckerContext.EMPTY);
+
+        assertThat(typed.value(), isTypedStringAddNode(
+            isTypedStringLiteralNode("a"),
+            isTypedStringLiteralNode("b")
+        ));
+        assertThat(typed.value().type(), equalTo(Types.STRING));
+    }
 }
-- 
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