From 5b999386f081b1f7e5259e26ffd33ea85e3e7a2b Mon Sep 17 00:00:00 2001
From: Michael Williamson <mike@zwobble.org>
Date: Wed, 12 Jul 2023 20:23:23 +0100
Subject: Add incomplete type-checking for if expressions

---
 .../org/shedlang/compiler/ast/untyped/Untyped.java | 18 +++++++
 .../compiler/typechecker/TypeCheckerIfTests.java   | 57 ++++++++++++++++++++++
 2 files changed, 75 insertions(+)
 create mode 100644 src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIfTests.java

(limited to 'src/test/java')

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 24ca7f87..8dddfa58 100644
--- a/src/test/java/org/shedlang/compiler/ast/untyped/Untyped.java
+++ b/src/test/java/org/shedlang/compiler/ast/untyped/Untyped.java
@@ -22,6 +22,10 @@ public class Untyped {
         );
     }
 
+    public static UntypedBlockNode block(List<UntypedFunctionStatementNode> statements) {
+        return new UntypedBlockNode(statements, Sources.NULL);
+    }
+
     public static UntypedBlockReturnNode blockReturn(UntypedExpressionNode expression) {
         return new UntypedBlockReturnNode(expression, Sources.NULL);
     }
@@ -50,6 +54,13 @@ public class Untyped {
         );
     }
 
+    public static UntypedConditionalBranchNode conditionalBranch(
+        UntypedExpressionNode condition,
+        UntypedBlockNode body
+    ) {
+        return new UntypedConditionalBranchNode(condition, body, Sources.NULL);
+    }
+
     public static UntypedBinaryOperationNode equals(
         UntypedExpressionNode left,
         UntypedExpressionNode right
@@ -70,6 +81,13 @@ public class Untyped {
         return new UntypedFunctionReturnNode(expression, Sources.NULL);
     }
 
+    public static UntypedIfNode if_(
+        List<UntypedConditionalBranchNode> conditionalBranches,
+        UntypedBlockNode elseBody
+    ) {
+        return new UntypedIfNode(conditionalBranches, elseBody, Sources.NULL);
+    }
+
     public static UntypedIntLiteralNode intLiteral(int value) {
         return new UntypedIntLiteralNode(BigInteger.valueOf(value), Sources.NULL);
     }
diff --git a/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIfTests.java b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIfTests.java
new file mode 100644
index 00000000..796dd7c9
--- /dev/null
+++ b/src/test/java/org/shedlang/compiler/typechecker/TypeCheckerIfTests.java
@@ -0,0 +1,57 @@
+package org.shedlang.compiler.typechecker;
+
+import org.junit.jupiter.api.Test;
+import org.shedlang.compiler.ast.untyped.Untyped;
+import org.shedlang.compiler.typechecker.errors.UnexpectedTypeError;
+import org.shedlang.compiler.typechecker.typesets.TypeSets;
+import org.shedlang.compiler.types.Types;
+
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.zwobble.precisely.AssertThat.assertThat;
+import static org.zwobble.precisely.Matchers.equalTo;
+
+public class TypeCheckerIfTests {
+    @Test
+    public void canTypeCheckIfWithAllBranchesGivingTheSameType() {
+        var untyped = Untyped.if_(
+            List.of(
+                Untyped.conditionalBranch(
+                    Untyped.boolLiteral(true),
+                    Untyped.block(List.of(
+                        Untyped.blockReturn(Untyped.stringLiteral("a"))
+                    ))
+                )
+            ),
+            Untyped.block(List.of(
+                Untyped.blockReturn(Untyped.stringLiteral("b"))
+            ))
+        );
+
+        var result = TypeChecker.typeCheckExpression(untyped, TypeCheckerContext.EMPTY);
+
+        assertThat(result.value().type(), equalTo(Types.STRING));
+    }
+
+    @Test
+    public void whenConditionIsNotBoolThenErrorIsThrown() {
+        var untyped = Untyped.if_(
+            List.of(
+                Untyped.conditionalBranch(
+                    Untyped.intLiteral(0),
+                    Untyped.block(List.of())
+                )
+            ),
+            Untyped.block(List.of())
+        );
+
+        var error = assertThrows(
+            UnexpectedTypeError.class,
+            () -> TypeChecker.typeCheckExpression(untyped, TypeCheckerContext.EMPTY)
+        );
+
+        assertThat(error.expected(), equalTo(TypeSets.type(Types.BOOL)));
+        assertThat(error.actual(), equalTo(Types.INT));
+    }
+}
-- 
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