Report lints about invalid Dart Templates in SQL

moor/test/database_test.dart

@@ -17,8 +17,9 @@ class _FakeDb extends GeneratedDatabase {
       },
       beforeOpen: (details) async {
         // this fake select query is verified via mocks
-        await customSelect(
+        await customSelectQuery(
-            'opened: ${details.versionBefore} to ${details.versionNow}');
+                'opened: ${details.versionBefore} to ${details.versionNow}')
+            .get();
       },
     );
   }

moor_generator/lib/src/analyzer/sql_queries/lints/linter.dart

@@ -2,6 +2,8 @@ import 'package:sqlparser/sqlparser.dart';
 
 import '../query_handler.dart';
 
+/// Provides additional hints that aren't implemented in the sqlparser because
+/// they're specific to moor.
 class Linter {
   final QueryHandler handler;
   final List<AnalysisError> lints = [];
@@ -18,6 +20,39 @@ class _LintingVisitor extends RecursiveVisitor<void> {
 
   _LintingVisitor(this.linter);
 
+  @override
+  void visitResultColumn(ResultColumn e) {
+    super.visitResultColumn(e);
+
+    if (e is ExpressionResultColumn) {
+      // The generated code will be invalid if knowing the expression is needed
+      // to know the column name (e.g. it's a Dart template without an AS), or
+      // if the type is unknown.
+      final expression = e.expression;
+      final resolveResult = linter.handler.context.typeOf(expression);
+
+      if (resolveResult.type == null) {
+        linter.lints.add(AnalysisError(
+          type: AnalysisErrorType.other,
+          message: 'Expression has an unknown type, the generated code can be'
+              ' inaccurate.',
+          relevantNode: expression,
+        ));
+      }
+
+      final dependsOnPlaceholder = e.as == null &&
+          expression.allDescendants.whereType<DartPlaceholder>().isNotEmpty;
+      if (dependsOnPlaceholder) {
+        linter.lints.add(AnalysisError(
+          type: AnalysisErrorType.other,
+          message: 'The name of this column depends on a Dart template, which '
+              'breaks generated code. Try adding an `AS` alias to fix this.',
+          relevantNode: e,
+        ));
+      }
+    }
+  }
+
   @override
   void visitInsertStatement(InsertStatement e) {
     final targeted = e.resolvedTargetColumns;

moor_generator/lib/src/analyzer/sql_queries/query_handler.dart

@@ -82,11 +82,11 @@ class QueryHandler {
       final type = context.typeOf(column).type;
       final moorType = mapper.resolvedToMoor(type);
       UsedTypeConverter converter;
-      if (type.hint is TypeConverterHint) {
+      if (type?.hint is TypeConverterHint) {
         converter = (type.hint as TypeConverterHint).converter;
       }
 
-      columns.add(ResultColumn(column.name, moorType, type.nullable,
+      columns.add(ResultColumn(column.name, moorType, type?.nullable ?? true,
           converter: converter));
 
       final table = _tableOfColumn(column);

moor_generator/lib/src/writer/queries/query_writer.dart

@@ -113,7 +113,8 @@ class QueryWriter {
   String _readingCode(ResultColumn column) {
     final readMethod = readFromMethods[column.type];
 
-    var code = "row.$readMethod('${column.name}')";
+    final dartLiteral = asDartLiteral(column.name);
+    var code = 'row.$readMethod($dartLiteral)';
 
     if (column.converter != null) {
       final converter = column.converter;

moor_generator/test/analyzer/sql_queries/linter_test.dart

@@ -0,0 +1,25 @@
+import 'package:moor_generator/src/analyzer/sql_queries/query_handler.dart';
+import 'package:moor_generator/src/analyzer/sql_queries/type_mapping.dart';
+import 'package:sqlparser/sqlparser.dart';
+import 'package:test/test.dart';
+
+void main() {
+  final engine = SqlEngine(useMoorExtensions: true);
+  final mapper = TypeMapper();
+
+  test('warns when a result column is unresolved', () {
+    final result = engine.analyze('SELECT ?;');
+    final moorQuery = QueryHandler('query', result, mapper).handle();
+
+    expect(moorQuery.lints,
+        anyElement((AnalysisError q) => q.message.contains('unknown type')));
+  });
+
+  test('warns when the result depends on a Dart template', () {
+    final result = engine.analyze(r"SELECT 'string' = $expr;");
+    final moorQuery = QueryHandler('query', result, mapper).handle();
+
+    expect(moorQuery.lints,
+        anyElement((AnalysisError q) => q.message.contains('Dart template')));
+  });
+}

sqlparser/lib/src/analysis/types/resolver.dart

@@ -62,7 +62,7 @@ class TypeResolver {
         // todo probably needs to be nullable when coming from a join?
         return ResolveResult(column.type);
       } else if (column is ExpressionColumn) {
-        return resolveExpression(column.expression);
+        return resolveOrInfer(column.expression);
       }
 
       throw StateError('Unknown column $column');