Throw error on duplicate variable name

3 files changed, 28 insertions, 7 deletions

diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/DuplicateVariableNameError.java b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/DuplicateVariableNameError.java
new file mode 100644
index 0000000..1fc79bf
--- /dev/null
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/DuplicateVariableNameError.java
@@ -0,0 +1,17 @@
+package org.zwobble.hobgoblin.compiler.typechecker;
+
+import org.zwobble.hobgoblin.compiler.errors.SourceError;
+import org.zwobble.hobgoblin.compiler.sources.Source;
+
+public class DuplicateVariableNameError extends SourceError {
+    private final String name;
+
+    public DuplicateVariableNameError(String name, Source source) {
+        super("A variable with the name " + name + " has already been declared", source);
+        this.name = name;
+    }
+
+    public String name() {
+        return name;
+    }
+}
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
index f313333..793e1f6 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeChecker.java
@@ -40,7 +40,7 @@ public class TypeChecker {
                         importedNamespace,
                         untypedImport.source()
                     ));
-                namespaceContext.declare(importedName, fieldType);
+                namespaceContext.declare(importedName, fieldType, untypedImport.source());
             }
         }
 
@@ -109,7 +109,7 @@ public class TypeChecker {
     ) {
         var nativeType = new EnumType(context.namespaceName(), untyped.name());
         var metaType = new TypeLevelValueType(nativeType);
-        context.declare(untyped.name(), metaType);
+        context.declare(untyped.name(), metaType, untyped.source());
         return metaType;
     }
 
@@ -146,7 +146,7 @@ public class TypeChecker {
     ) {
         var nativeType = new SimpleNativeType(context.namespaceName(), untyped.name());
         var metaType = new TypeLevelValueType(nativeType);
-        context.declare(untyped.name(), metaType);
+        context.declare(untyped.name(), metaType, untyped.source());
         return metaType;
     }
 
@@ -169,7 +169,7 @@ public class TypeChecker {
     ) {
         var structType = new StructType(context.namespaceName(), untyped.name());
         var metaType = new TypeLevelValueType(structType);
-        context.declare(untyped.name(), metaType);
+        context.declare(untyped.name(), metaType, untyped.source());
         return metaType;
     }
 
@@ -233,7 +233,7 @@ public class TypeChecker {
     ) {
         var sumType = new SumType(context.namespaceName(), untyped.name());
         var metaType = new TypeLevelValueType(sumType);
-        context.declare(untyped.name(), metaType);
+        context.declare(untyped.name(), metaType, untyped.source());
         return metaType;
     }
 
diff --git a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerNamespaceContext.java b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerNamespaceContext.java
index 82c8273..51e11d6 100644
--- a/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerNamespaceContext.java
+++ b/src/main/java/org/zwobble/hobgoblin/compiler/typechecker/TypeCheckerNamespaceContext.java
@@ -1,5 +1,6 @@
 package org.zwobble.hobgoblin.compiler.typechecker;
 
+import org.zwobble.hobgoblin.compiler.sources.Source;
 import org.zwobble.hobgoblin.compiler.types.*;
 
 import java.util.HashMap;
@@ -43,8 +44,11 @@ public class TypeCheckerNamespaceContext {
         return this.namespaceName;
     }
 
-    public void declare(String name, Type type) {
-        // TODO: Check variable is not already declared.
+    public void declare(String name, Type type, Source source) {
+        if (this.variables.containsKey(name)) {
+            throw new DuplicateVariableNameError(name, source);
+        }
+
         this.variables.put(name, type);
     }