Check positional arg type matches param type

7 files changed, 98 insertions, 5 deletions

diff --git a/src/main/java/org/shedlang/compiler/ast/typed/TypedExpressionNode.java b/src/main/java/org/shedlang/compiler/ast/typed/TypedExpressionNode.java
index 0c61b3b2..4bb9cb8e 100644
--- a/src/main/java/org/shedlang/compiler/ast/typed/TypedExpressionNode.java
+++ b/src/main/java/org/shedlang/compiler/ast/typed/TypedExpressionNode.java
@@ -3,6 +3,7 @@ package org.shedlang.compiler.ast.typed;
 import org.shedlang.compiler.types.Type;
 
 public sealed interface TypedExpressionNode
+    extends TypedNode
     permits TypedBoolLiteralNode, TypedCallNode, TypedIntLiteralNode, TypedReferenceNode, TypedStringLiteralNode {
     Type type();
 }
diff --git a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
index d4704a4e..ebfdc0d5 100644
--- a/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/shedlang/compiler/typechecker/TypeChecker.java
@@ -2,18 +2,38 @@ package org.shedlang.compiler.typechecker;
 
 import org.shedlang.compiler.ast.typed.*;
 import org.shedlang.compiler.ast.untyped.*;
+import org.shedlang.compiler.typechecker.typesets.TypeSets;
 import org.shedlang.compiler.types.FunctionType;
+import org.shedlang.compiler.types.Type;
 
 public class TypeChecker {
     private TypeChecker() {
     }
 
-    private static TypedArgsNode typeCheckArgs(UntypedArgsNode args, TypeCheckerContext context) {
-        var typedPositional = args.positional().stream()
+    private static void checkIsSubType(TypedExpressionNode expression, Type expectedType, TypeCheckerContext context) {
+        if (!isSubType(expression.type(), expectedType, context)) {
+            throw new UnexpectedTypeError(
+                TypeSets.type(expectedType),
+                expression.type(),
+                expression.source()
+            );
+        }
+    }
+
+    private static boolean isSubType(Type subType, Type superType, TypeCheckerContext context) {
+        return subType.equals(superType);
+    }
+
+    private static TypedArgsNode typeCheckArgs(
+        UntypedArgsNode args,
+        TypeCheckerContext context,
+        FunctionType receiverType
+    ) {
+        var typedPositionalArgs = args.positional().stream()
             .map(arg -> typeCheckExpression(arg, context))
             .toList();
 
-        var typedNamed = args.named().stream()
+        var typedNamedArgs = args.named().stream()
             .map(arg -> new TypedNamedArgNode(
                 arg.name(),
                 typeCheckExpression(arg.expression(), context),
@@ -21,7 +41,14 @@ public class TypeChecker {
             ))
             .toList();
 
-        return new TypedArgsNode(typedPositional, typedNamed, args.source());
+        for (var i = 0; i < typedPositionalArgs.size(); i++) {
+            var typedArg = typedPositionalArgs.get(i);
+            var paramType = receiverType.positionalParams().get(i);
+
+            checkIsSubType(typedArg, paramType, context);
+        }
+
+        return new TypedArgsNode(typedPositionalArgs, typedNamedArgs, args.source());
     }
 
     public static TypedExpressionNode typeCheckBoolLiteral(
@@ -42,7 +69,7 @@ public class TypeChecker {
 
         return new TypedCallNode(
             typedReceiver,
-            typeCheckArgs(untyped.args(), context),
+            typeCheckArgs(untyped.args(), context, receiverType),
             false,
             receiverType.returnType(),
             untyped.source()
diff --git a/src/main/java/org/shedlang/compiler/typechecker/UnexpectedTypeError.java b/src/main/java/org/shedlang/compiler/typechecker/UnexpectedTypeError.java
new file mode 100644
index 00000000..51cc6652
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/typechecker/UnexpectedTypeError.java
@@ -0,0 +1,25 @@
+package org.shedlang.compiler.typechecker;
+
+import org.shedlang.compiler.errors.SourceError;
+import org.shedlang.compiler.sources.Source;
+import org.shedlang.compiler.typechecker.typesets.TypeSet;
+import org.shedlang.compiler.types.Type;
+
+public class UnexpectedTypeError extends SourceError {
+    private final TypeSet expected;
+    private final Type actual;
+
+    public UnexpectedTypeError(TypeSet expected, Type actual, Source source) {
+        super("Expected " + expected.describe() + " but was " + actual.describe(), source);
+        this.expected = expected;
+        this.actual = actual;
+    }
+
+    public TypeSet expected() {
+        return expected;
+    }
+
+    public Type actual() {
+        return actual;
+    }
+}
diff --git a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSet.java b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSet.java
new file mode 100644
index 00000000..79cb0433
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSet.java
@@ -0,0 +1,5 @@
+package org.shedlang.compiler.typechecker.typesets;
+
+public sealed interface TypeSet permits TypeSetFunction, TypeSetType {
+    String describe();
+}
diff --git a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetFunction.java b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetFunction.java
new file mode 100644
index 00000000..127c0e71
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetFunction.java
@@ -0,0 +1,13 @@
+package org.shedlang.compiler.typechecker.typesets;
+
+public final class TypeSetFunction implements TypeSet {
+    static final TypeSetFunction INSTANCE = new TypeSetFunction();
+
+    private TypeSetFunction() {
+    }
+
+    @Override
+    public String describe() {
+        return "function";
+    }
+}
diff --git a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetType.java b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetType.java
new file mode 100644
index 00000000..f067351a
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSetType.java
@@ -0,0 +1,10 @@
+package org.shedlang.compiler.typechecker.typesets;
+
+import org.shedlang.compiler.types.Type;
+
+public record TypeSetType(Type type) implements TypeSet {
+    @Override
+    public String describe() {
+        return type.describe();
+    }
+}
diff --git a/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java
new file mode 100644
index 00000000..4f5f1848
--- /dev/null
+++ b/src/main/java/org/shedlang/compiler/typechecker/typesets/TypeSets.java
@@ -0,0 +1,12 @@
+package org.shedlang.compiler.typechecker.typesets;
+
+import org.shedlang.compiler.types.Type;
+
+public class TypeSets {
+    private TypeSets() {
+    }
+
+    public static TypeSet type(Type type) {
+        return new TypeSetType(type);
+    }
+}