Move LSP semantics into typed analysis

internal/lang/diagnostics_test.go

@@ -0,0 +1,37 @@
+package lang
+
+import "testing"
+
+func TestAnalyzeProducesStructuredUndefinedDiagnostic(t *testing.T) {
+	source := `package demo fun main() { println(missing) }`
+	program, err := Parse(source)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, diagnostics := AnalyzeWithContext(program, nil)
+	if len(diagnostics) != 1 {
+		t.Fatalf("diagnostics = %#v", diagnostics)
+	}
+	diagnostic := diagnostics[0]
+	if diagnostic.Code != "undefined-symbol" || diagnostic.Severity != DiagnosticError || diagnostic.Message != "undefined identifier missing" {
+		t.Fatalf("unexpected diagnostic: %#v", diagnostic)
+	}
+	if got := source[diagnostic.Span.Start:diagnostic.Span.End]; got != "missing" {
+		t.Fatalf("diagnostic span = %q", got)
+	}
+}
+
+func TestAnalyzeUsesAdditionalPackagePrograms(t *testing.T) {
+	current, err := Parse(`package demo fun main() { helper() }`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	sibling, err := Parse(`package demo fun helper() { println("ok") }`)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, diagnostics := AnalyzeWithContext(current, []*Program{sibling})
+	if len(diagnostics) != 0 {
+		t.Fatalf("package symbol was not resolved: %#v", diagnostics)
+	}
+}