Better column name prediction for expressions

sqlparser/lib/src/analysis/analysis.dart

@@ -12,6 +12,7 @@ part 'steps/column_resolver.dart';
 part 'steps/reference_finder.dart';
 part 'steps/reference_resolver.dart';
 part 'steps/set_parent_visitor.dart';
+part 'steps/type_resolver.dart';
 
 part 'types/data.dart';
 part 'types/resolution.dart';

sqlparser/lib/src/analysis/context.dart

@@ -3,8 +3,9 @@ part of 'analysis.dart';
 class AnalysisContext {
   final List<AnalysisError> errors = [];
   final AstNode root;
+  final String sql;
 
-  AnalysisContext(this.root);
+  AnalysisContext(this.root, this.sql);
 
   void reportError(AnalysisError error) {
     errors.add(error);

sqlparser/lib/src/analysis/steps/column_resolver.dart

@@ -75,8 +75,12 @@ class ColumnResolver extends RecursiveVisitor<void> {
       return (c.expression as Reference).columnName;
     }
 
-    // todo I think in this case it's just the literal lexeme?
-    return 'TODO';
+    // in this case it's just the literal expression. So for instance,
+    // "SELECT 3+  5" has a result column called "3+ 5" (consecutive whitespace
+    // is removed).
+    final span = context.sql.substring(c.firstPosition, c.lastPosition);
+    // todo remove consecutive whitespace
+    return span;
   }
 
   void _resolveTableReference(TableReference r) {

sqlparser/lib/src/analysis/steps/type_resolver.dart

@@ -0,0 +1,3 @@
+part of '../analysis.dart';
+
+class TypeResolver extends RecursiveVisitor<void> {}

sqlparser/lib/src/ast/ast.dart

@@ -24,6 +24,20 @@ abstract class AstNode {
   /// by the analyzer after the tree has been parsed.
   AstNode parent;
 
+  Token first;
+  Token last;
+
+  /// The first index in the source that belongs to this node
+  int get firstPosition => first.span.start.offset;
+
+  /// The last position that belongs to node, exclusive
+  int get lastPosition => last.span.end.offset;
+
+  void setSpan(Token first, Token last) {
+    this.first = first;
+    this.last = last;
+  }
+
   Iterable<AstNode> get parents sync* {
     var node = parent;
     while (node != null) {

sqlparser/lib/src/engine/sql_engine.dart

@@ -44,7 +44,7 @@ class SqlEngine {
     final node = parse(sql);
     const SetParentVisitor().startAtRoot(node);
 
-    final context = AnalysisContext(node);
+    final context = AnalysisContext(node, sql);
     final scope = _constructRootScope();
 
     ReferenceFinder(globalScope: scope).start(node);

sqlparser/lib/src/reader/parser/parser.dart

@@ -99,6 +99,7 @@ class Parser {
   /// https://www.sqlite.org/lang_select.html
   SelectStatement select() {
     if (!_match(const [TokenType.select])) return null;
+    final selectToken = _previous;
 
     var distinct = false;
     if (_matchOne(TokenType.distinct)) {
@@ -127,14 +128,14 @@ class Parser {
       groupBy: groupBy,
       orderBy: orderBy,
       limit: limit,
-    );
+    )..setSpan(selectToken, _previous);
   }
 
   /// Parses a [ResultColumn] or throws if none is found.
   /// https://www.sqlite.org/syntax/result-column.html
   ResultColumn _resultColumn() {
     if (_match(const [TokenType.star])) {
-      return StarResultColumn(null);
+      return StarResultColumn(null)..setSpan(_previous, _previous);
     }
 
     final positionBefore = _current;
@@ -146,7 +147,8 @@ class Parser {
       final identifier = _previous;
 
       if (_match(const [TokenType.dot]) && _match(const [TokenType.star])) {
-        return StarResultColumn((identifier as IdentifierToken).identifier);
+        return StarResultColumn((identifier as IdentifierToken).identifier)
+          ..setSpan(identifier, _previous);
       }
 
       // not a star result column. go back and parse the expression.
@@ -155,10 +157,13 @@ class Parser {
       _current = positionBefore;
     }
 
+    final tokenBefore = _peek;
+
     final expr = expression();
     final as = _as();
 
-    return ExpressionResultColumn(expression: expr, as: as?.identifier);
+    return ExpressionResultColumn(expression: expr, as: as?.identifier)
+      ..setSpan(tokenBefore, _previous);
   }
 
   /// Returns an identifier followed after an optional "AS" token in sql.

sqlparser/test/analysis/reference_resolver_test.dart

@@ -21,13 +21,14 @@ void main() {
     );
     final engine = SqlEngine()..registerTable(demoTable);
 
-    final context = engine.analyze('SELECT id, d.content, * FROM demo AS d');
+    final context =
+        engine.analyze('SELECT id, d.content, *, 3 + 4 FROM demo AS d');
 
     final select = context.root as SelectStatement;
     final resolvedColumns = select.resolvedColumns;
 
-    expect(
-        resolvedColumns.map((c) => c.name), ['id', 'content', 'id', 'content']);
+    expect(resolvedColumns.map((c) => c.name),
+        ['id', 'content', 'id', 'content', '3 + 4']);
 
     final firstColumn = select.columns[0] as ExpressionResultColumn;
     final secondColumn = select.columns[1] as ExpressionResultColumn;