diff --git a/prometeu-compiler/prometeu-compiler-core/src/main/java/p/studio/compiler/source/diagnostics/DiagnosticSink.java b/prometeu-compiler/prometeu-compiler-core/src/main/java/p/studio/compiler/source/diagnostics/DiagnosticSink.java
index ba562483..956cfdfd 100644
--- a/prometeu-compiler/prometeu-compiler-core/src/main/java/p/studio/compiler/source/diagnostics/DiagnosticSink.java
+++ b/prometeu-compiler/prometeu-compiler-core/src/main/java/p/studio/compiler/source/diagnostics/DiagnosticSink.java
@@ -1,4 +1,92 @@
 package p.studio.compiler.source.diagnostics;
 
-public class DiagnosticSink {
+import p.studio.compiler.source.Span;
+import p.studio.utilities.structures.ReadOnlyCollection;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+
+public class DiagnosticSink extends ReadOnlyCollection<Diagnostic> {
+    private int errorCount = 0;
+    private int warningCount = 0;
+
+    protected DiagnosticSink() {
+        super(new ArrayList<>());
+    }
+
+    public static DiagnosticSink empty() {
+        return new DiagnosticSink();
+    }
+
+    public DiagnosticSink report(final Diagnostic diagnostic) {
+        Objects.requireNonNull(diagnostic);
+        if (diagnostic.getSeverity().isError()) {
+            errorCount++;
+        } else {
+            warningCount++;
+        }
+        collection.add(diagnostic);
+        return this;
+    }
+
+    public DiagnosticSink report(
+            final Severity severity,
+            final String code,
+            final String message,
+            final Span span) {
+        return report(severity, code, message, span, List.of());
+    }
+
+    public DiagnosticSink report(
+            final Severity severity,
+            final String code,
+            final String message,
+            final Span span,
+            final List<RelatedSpan> related) {
+        return report(new Diagnostic(
+                Objects.requireNonNull(severity),
+                Objects.requireNonNull(code),
+                Objects.requireNonNull(message),
+                Objects.requireNonNull(span),
+                List.copyOf(Objects.requireNonNull(related))));
+    }
+
+    public DiagnosticSink error(
+            final String code,
+            final String message,
+            final Span span) {
+        return report(Severity.Error, code, message, span);
+    }
+
+    public DiagnosticSink warning(
+            final String code,
+            final String message,
+            final Span span) {
+        return report(Severity.Warning, code, message, span);
+    }
+
+    public DiagnosticSink merge(final DiagnosticSink diagnostics) {
+        Objects.requireNonNull(diagnostics);
+        for (final Diagnostic diagnostic : diagnostics) {
+            report(diagnostic);
+        }
+        return this;
+    }
+
+    public boolean hasErrors() {
+        return errorCount > 0;
+    }
+
+    public boolean hasWarnings() {
+        return warningCount > 0;
+    }
+
+    public int errorCount() {
+        return errorCount;
+    }
+
+    public int warningCount() {
+        return warningCount;
+    }
 }
diff --git a/prometeu-compiler/prometeu-compiler-core/src/test/java/p/studio/compiler/source/diagnostics/DiagnosticSinkTest.java b/prometeu-compiler/prometeu-compiler-core/src/test/java/p/studio/compiler/source/diagnostics/DiagnosticSinkTest.java
new file mode 100644
index 00000000..94f17fac
--- /dev/null
+++ b/prometeu-compiler/prometeu-compiler-core/src/test/java/p/studio/compiler/source/diagnostics/DiagnosticSinkTest.java
@@ -0,0 +1,42 @@
+package p.studio.compiler.source.diagnostics;
+
+import org.junit.jupiter.api.Test;
+import p.studio.compiler.source.Span;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class DiagnosticSinkTest {
+
+    @Test
+    void shouldReportAndCountDiagnostics() {
+        final var sink = DiagnosticSink.empty();
+
+        sink.error("E001", "Unknown symbol", Span.none());
+        sink.warning("W001", "Unused declaration", Span.none());
+
+        assertEquals(2, sink.size());
+        assertTrue(sink.hasErrors());
+        assertTrue(sink.hasWarnings());
+        assertEquals(1, sink.errorCount());
+        assertEquals(1, sink.warningCount());
+    }
+
+    @Test
+    void shouldMergeDiagnostics() {
+        final var a = DiagnosticSink.empty()
+                .warning("W010", "Unused import", Span.none());
+        final var b = DiagnosticSink.empty()
+                .error("E999", "Invalid type", Span.none());
+
+        a.merge(b);
+
+        assertEquals(2, a.size());
+        assertTrue(a.hasErrors());
+        assertTrue(a.hasWarnings());
+        assertEquals(1, a.errorCount());
+        assertEquals(1, a.warningCount());
+        assertEquals(1, b.errorCount());
+        assertEquals(0, b.warningCount());
+    }
+}