Start with type resolution

sqlparser/lib/src/analysis/analysis.dart

@@ -15,7 +15,7 @@ part 'steps/set_parent_visitor.dart';
 part 'steps/type_resolver.dart';
 
 part 'types/data.dart';
-part 'types/resolution.dart';
+part 'types/resolver.dart';
 
 part 'types/typeable.dart';
 

sqlparser/lib/src/analysis/context.dart

@@ -4,6 +4,7 @@ class AnalysisContext {
   final List<AnalysisError> errors = [];
   final AstNode root;
   final String sql;
+  final TypeResolver types = TypeResolver();
 
   AnalysisContext(this.root, this.sql);
 

sqlparser/lib/src/analysis/functions/core.dart

@@ -1,9 +1,16 @@
 part of '../analysis.dart';
 
 // https://www.sqlite.org/lang_corefunc.html
-final abs = StaticTypeFunction(
-    name: 'ABS', inputs: [NumericType()], output: NumericType());
+final abs = _AbsFunction();
 
-final coreFunctions = [
+class _AbsFunction extends SqlFunction {
+  _AbsFunction() : super('ABS');
+
+  @override
+  void register(AnalysisContext context, Typeable functionCall,
+      List<Typeable> parameters) {}
+}
+
+final coreFunctions = <SqlFunction>[
   abs,
 ];

sqlparser/lib/src/analysis/functions/function.dart

@@ -1,16 +1,19 @@
 part of '../analysis.dart';
 
-class SqlFunction with Referencable, VisibleToChildren {
+abstract class SqlFunction with Referencable, VisibleToChildren {
   final String name;
 
   SqlFunction(this.name);
+
+  void register(AnalysisContext context, Typeable functionCall,
+      List<Typeable> parameters);
 }
 
-class StaticTypeFunction extends SqlFunction {
+/*class StaticTypeFunction extends SqlFunction {
   final List<SqlType> inputs;
   final SqlType output;
 
   StaticTypeFunction(
       {@required String name, @required this.inputs, @required this.output})
       : super(name);
-}
+}*/

sqlparser/lib/src/analysis/schema/column.dart

@@ -1,6 +1,6 @@
 part of '../analysis.dart';
 
-abstract class Column with Referencable, Typeable {
+abstract class Column with Referencable implements Typeable {
   String get name;
 }
 

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

@@ -1,3 +1,116 @@
 part of '../analysis.dart';
 
-class TypeResolver extends RecursiveVisitor<void> {}
+const _comparisons = [
+  TokenType.less,
+  TokenType.lessEqual,
+  TokenType.more,
+  TokenType.moreEqual,
+  TokenType.equal,
+  TokenType.doubleEqual,
+  TokenType.exclamationEqual,
+  TokenType.lessMore,
+];
+
+class TypeResolvingVisitor extends RecursiveVisitor<void> {
+  final AnalysisContext context;
+  TypeResolver get types => context.types;
+
+  TypeResolvingVisitor(this.context);
+
+  @override
+  void visitSelectStatement(SelectStatement e) {
+    if (e.where != null) {
+      context.types.suggestBool(e.where);
+    }
+
+    visitChildren(e);
+  }
+
+  @override
+  void visitResultColumn(ResultColumn e) {
+    visitChildren(e);
+  }
+
+  @override
+  void visitFunction(FunctionExpression e) {
+    // todo handle function calls
+    visitChildren(e);
+  }
+
+  @override
+  void visitLimit(Limit e) {
+    if (e.count != null) {
+      types.suggestType(e.count, const SqlType.int());
+    }
+    if (e.offset != null) {
+      types.suggestType(e.offset, const SqlType.int());
+    }
+
+    visitChildren(e);
+  }
+
+  @override
+  void visitBinaryExpression(BinaryExpression e) {
+    final operator = e.operator.type;
+    if (operator == TokenType.doublePipe) {
+      // string concatenation: Will return a string, makes most sense with a
+      // string.
+      types
+        ..forceType(e, const SqlType.text())
+        ..suggestType(e.left, const SqlType.text())
+        ..suggestType(e.right, const SqlType.text());
+    } else if (operator == TokenType.and || operator == TokenType.or) {
+      types
+        ..suggestBool(e.left)
+        ..suggestBool(e.right)
+        ..forceType(e, const SqlType.int())
+        ..addTypeHint(e, const IsBoolean());
+    } else if (_comparisons.contains(operator)) {
+      types
+        ..suggestBool(e)
+        ..suggestSame(e.left, e.right);
+    } else {
+      // arithmetic operator
+      types
+        ..forceType(e, const AnyNumericType())
+        ..suggestType(e.right, const AnyNumericType())
+        ..suggestType(e.left, const AnyNumericType());
+    }
+
+    visitChildren(e);
+  }
+
+  @override
+  void visitUnaryExpression(UnaryExpression e) {
+    final operator = e.operator.type;
+    if (operator == TokenType.plus) {
+      // unary type does nothing, just returns the value
+      types.suggestSame(e, e.inner);
+    } else if (operator == TokenType.minus) {
+      types
+        ..forceType(e, const AnyNumericType())
+        ..suggestType(e.inner, const AnyNumericType());
+    }
+
+    visitChildren(e);
+  }
+
+  @override
+  void visitLiteral(Literal e) {
+    if (e is NullLiteral) {
+      types.forceType(e, const SqlType.nullType());
+    } else if (e is NumericLiteral) {
+      if (e.number.toInt() == e.number) {
+        types.forceType(e, const SqlType.int());
+      } else {
+        types.forceType(e, const SqlType.real());
+      }
+
+      if (e is BooleanLiteral) {
+        types.addTypeHint(e, const IsBoolean());
+      }
+    }
+
+    visitChildren(e);
+  }
+}

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

@@ -1,25 +1,72 @@
 part of '../analysis.dart';
 
 /// A type that sql expressions can have at runtime.
-abstract class SqlType {}
+abstract class SqlType {
+  const SqlType();
+  const factory SqlType.nullType() = NullType._;
+  const factory SqlType.int() = IntegerType._;
+  const factory SqlType.real() = RealType._;
+  const factory SqlType.text() = TextType._;
+  const factory SqlType.blob() = BlobType._;
 
-class NullType extends SqlType {}
+  bool isSubTypeOf(SqlType other);
+}
 
-class NumericType extends SqlType {}
+class NullType extends SqlType {
+  const NullType._();
 
-class IntegerType extends NumericType {}
+  @override
+  bool isSubTypeOf(SqlType other) => true;
+}
 
-class RealType extends NumericType {}
+class IntegerType extends SqlType {
+  const IntegerType._();
 
-class TextType extends SqlType {}
+  @override
+  bool isSubTypeOf(SqlType other) => other is IntegerType;
+}
 
-class BlobType extends SqlType {}
+class RealType extends SqlType {
+  const RealType._();
+
+  @override
+  bool isSubTypeOf(SqlType other) => other is RealType;
+}
+
+class TextType extends SqlType {
+  const TextType._();
+
+  @override
+  bool isSubTypeOf(SqlType other) => other is TextType;
+}
+
+class BlobType extends SqlType {
+  const BlobType._();
+
+  @override
+  bool isSubTypeOf(SqlType other) => other is BlobType;
+}
+
+class AnyNumericType extends SqlType {
+  const AnyNumericType();
+
+  @override
+  bool isSubTypeOf(SqlType other) {
+    return other is RealType || other is IntegerType;
+  }
+}
 
 /// Provides more precise hints than the [SqlType]. For instance, booleans are
 /// stored as ints in sqlite, but it might be desirable to know whether an
 /// expression will actually be a boolean.
-abstract class TypeHint {}
+abstract class TypeHint {
+  const TypeHint();
+}
 
-class IsBoolean extends TypeHint {}
+class IsBoolean extends TypeHint {
+  const IsBoolean();
+}
 
-class IsDateTime extends TypeHint {}
+class IsDateTime extends TypeHint {
+  const IsDateTime();
+}

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

@@ -1,3 +0,0 @@
-part of '../analysis.dart';
-
-class TypeResolutionState {}

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

@@ -0,0 +1,49 @@
+part of '../analysis.dart';
+
+/// Attempts to resolve types of expressions, result columns and variables.
+/// As sqlite is pretty lenient at typing and pretty much accepts every value
+/// everywhere, this
+class TypeResolver {
+  final Map<Typeable, _ResolvingState> _matchedStates = {};
+
+  _ResolvingState _stateFor(Typeable typeable) {
+    return _matchedStates.putIfAbsent(
+        typeable, () => _ResolvingState(typeable, this));
+  }
+
+  void finish() {}
+
+  /// Suggest that [t] should have the type [type].
+  void suggestType(Typeable t, SqlType type) {
+    _stateFor(t).suggested.add(type);
+  }
+
+  void suggestSame(Typeable a, Typeable b) {}
+
+  void suggestBool(Typeable t) {
+    final state = _stateFor(t);
+    state.suggested.add(const SqlType.int());
+    state.hints.add(const IsBoolean());
+  }
+
+  /// Marks that [t] will definitely have the type [type].
+  void forceType(Typeable t, SqlType type) {
+    _stateFor(t).forced = type;
+  }
+
+  /// Add an additional hint
+  void addTypeHint(Typeable t, TypeHint hint) {
+    _stateFor(t).hints.add(hint);
+  }
+}
+
+class _ResolvingState {
+  final Typeable typeable;
+  final TypeResolver resolver;
+
+  final List<TypeHint> hints = [];
+  final List<SqlType> suggested = [];
+  SqlType forced;
+
+  _ResolvingState(this.typeable, this.resolver);
+}

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

@@ -1,6 +1,4 @@
 part of '../analysis.dart';
 
 /// Something that has a type.
-mixin Typeable {
-  TypeResolutionState resolutionState;
-}
+abstract class Typeable {}

sqlparser/lib/src/ast/expressions/expressions.dart

@@ -1,3 +1,3 @@
 part of '../ast.dart';
 
-abstract class Expression extends AstNode {}
+abstract class Expression extends AstNode implements Typeable {}

sqlparser/lib/src/engine/sql_engine.dart

@@ -48,7 +48,10 @@ class SqlEngine {
     final scope = _constructRootScope();
 
     ReferenceFinder(globalScope: scope).start(node);
-    node..accept(ColumnResolver(context))..accept(ReferenceResolver(context));
+    node
+      ..accept(ColumnResolver(context))
+      ..accept(ReferenceResolver(context))
+      ..accept(TypeResolvingVisitor(context));
 
     return context;
   }