Macro expander integrated in binder
This commit is contained in:
Michael Schimmel
@@ -1,269 +0,0 @@
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unit Myc.Ast.MacroExpander;
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interface
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uses
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System.SysUtils,
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System.Classes,
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System.Generics.Collections,
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Myc.Data.Value,
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Myc.Ast.Nodes,
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Myc.Ast.Scope,
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Myc.Ast.Visitor;
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type
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// Defines the strategy for compiling and evaluating an AST node at compile time.
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TCompileTimeExecutor = reference to function(const ANode: IAstNode): TDataValue;
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IMacroExpander = interface(IAstVisitor)
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function Execute(const RootNode: IAstNode): IAstNode;
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end;
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// The macro expander is now a pure AST transformation engine.
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TMacroExpander = class(TAstTransformer, IMacroExpander)
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private
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FMacros: TDictionary<string, IMacroDefinitionNode>;
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FExecutor: TCompileTimeExecutor;
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function ExpandNode(const ANode: IAstNode): IAstNode;
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protected
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function VisitMacroDefinition(const Node: IMacroDefinitionNode): TDataValue; override;
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function VisitFunctionCall(const Node: IFunctionCallNode): TDataValue; override;
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public
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constructor Create(const AExecutor: TCompileTimeExecutor);
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destructor Destroy; override;
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function Execute(const RootNode: IAstNode): IAstNode;
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end;
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implementation
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uses
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Myc.Ast;
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type
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TExpansionHelper = class(TAstTransformer)
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private
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FExpansionScope: IExecutionScope;
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FExpander: TMacroExpander;
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FExecutor: TCompileTimeExecutor;
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protected
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function VisitUnquote(const Node: IUnquoteNode): TDataValue; override;
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function VisitUnquoteSplicing(const Node: IUnquoteSplicingNode): TDataValue; override;
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function VisitFunctionCall(const Node: IFunctionCallNode): TDataValue; override;
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public
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constructor Create(AExpansionScope: IExecutionScope; AExpander: TMacroExpander; AExecutor: TCompileTimeExecutor);
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class function Expand(
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Node: IAstNode;
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ExpansionScope: IExecutionScope;
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Expander: TMacroExpander;
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Executor: TCompileTimeExecutor
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): IAstNode; static;
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end;
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TSubstitutor = class(TAstTransformer)
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private
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FParamScope: IExecutionScope;
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protected
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function VisitIdentifier(const Node: IIdentifierNode): TDataValue; override;
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public
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constructor Create(AParamScope: IExecutionScope);
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end;
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{ TMacroExpander }
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constructor TMacroExpander.Create(const AExecutor: TCompileTimeExecutor);
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begin
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inherited Create;
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Assert(Assigned(AExecutor), 'A TCompileTimeExecutor must be provided.');
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FMacros := TDictionary<string, IMacroDefinitionNode>.Create;
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FExecutor := AExecutor;
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end;
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destructor TMacroExpander.Destroy;
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begin
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FMacros.Free;
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inherited;
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end;
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function TMacroExpander.ExpandNode(const ANode: IAstNode): IAstNode;
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var
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lastNode: IAstNode;
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begin
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Result := ANode;
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if not Assigned(Result) then
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exit;
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repeat
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lastNode := Result;
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Result := Self.Accept(lastNode).AsIntf<IAstNode>;
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until Result = lastNode;
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end;
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function TMacroExpander.Execute(const RootNode: IAstNode): IAstNode;
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begin
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FMacros.Clear;
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Result := ExpandNode(RootNode);
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end;
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function TMacroExpander.VisitFunctionCall(const Node: IFunctionCallNode): TDataValue;
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var
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macroDef: IMacroDefinitionNode;
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expandedNode: IAstNode;
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i: Integer;
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begin
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if not (Node.Callee is TIdentifierNode) then
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begin
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Result := inherited VisitFunctionCall(Node);
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exit;
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end;
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var calleeIdentifier := Node.Callee as TIdentifierNode;
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if FMacros.TryGetValue(calleeIdentifier.Name, macroDef) then
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begin
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var expansionScope := TAst.CreateScope(nil); // Temporary scope for parameters, no parent needed.
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if Length(Node.Arguments) <> Length(macroDef.Parameters) then
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raise Exception.CreateFmt(
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'Macro %s expects %d arguments, but got %d',
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[macroDef.Name.Name, Length(macroDef.Parameters), Length(Node.Arguments)]);
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for i := 0 to High(macroDef.Parameters) do
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expansionScope.Define(macroDef.Parameters[i].Name, TDataValue.FromIntf<IAstNode>(Node.Arguments[i]));
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if not (macroDef.Body is TQuasiquoteNode) then
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raise Exception.CreateFmt('Macro body for "%s" must be a quasiquoted expression.', [macroDef.Name.Name]);
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expandedNode := TExpansionHelper.Expand(IQuasiquoteNode(macroDef.Body).Expression, expansionScope, Self, FExecutor);
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Result := Self.Accept(expandedNode);
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end
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else
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begin
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Result := inherited VisitFunctionCall(Node);
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end;
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end;
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function TMacroExpander.VisitMacroDefinition(const Node: IMacroDefinitionNode): TDataValue;
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begin
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FMacros.AddOrSetValue(Node.Name.Name, Node);
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Result := TDataValue.FromIntf<IBlockExpressionNode>(TBlockExpressionNode.Create([]));
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end;
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{ TExpansionHelper }
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constructor TExpansionHelper.Create(AExpansionScope: IExecutionScope; AExpander: TMacroExpander; AExecutor: TCompileTimeExecutor);
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begin
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inherited Create;
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FExpansionScope := AExpansionScope;
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FExpander := AExpander;
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FExecutor := AExecutor;
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end;
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class function TExpansionHelper.Expand(
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Node: IAstNode;
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ExpansionScope: IExecutionScope;
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Expander: TMacroExpander;
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Executor: TCompileTimeExecutor
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): IAstNode;
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var
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helper: TExpansionHelper;
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begin
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helper := TExpansionHelper.Create(ExpansionScope, Expander, Executor);
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try
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Result := helper.Accept(Node).AsIntf<IAstNode>;
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finally
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helper.Free;
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end;
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end;
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function TExpansionHelper.VisitFunctionCall(const Node: IFunctionCallNode): TDataValue;
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var
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newArgs: TList<IAstNode>;
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transformedArgValue: TDataValue;
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transformedArgNode: IAstNode;
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transformedCallee: IAstNode;
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begin
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newArgs := TList<IAstNode>.Create;
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try
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for var arg in Node.Arguments do
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begin
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transformedArgValue := Self.Accept(arg);
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if transformedArgValue.IsVoid then
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continue;
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transformedArgNode := transformedArgValue.AsIntf<IAstNode>;
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if (transformedArgNode is TBlockExpressionNode) then
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newArgs.AddRange((transformedArgNode as TBlockExpressionNode).Expressions)
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else
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newArgs.Add(transformedArgNode);
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end;
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transformedCallee := Self.Accept(Node.Callee).AsIntf<IAstNode>;
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Result := TDataValue.FromIntf<IAstNode>(TAst.FunctionCall(transformedCallee, newArgs.ToArray));
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finally
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newArgs.Free;
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end;
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end;
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function TExpansionHelper.VisitUnquote(const Node: IUnquoteNode): TDataValue;
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var
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substitutor: TSubstitutor;
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substitutedAst, expandedAst: IAstNode;
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value: TDataValue;
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begin
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// Step 1: Substitute macro parameters with their AST node values.
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substitutor := TSubstitutor.Create(FExpansionScope);
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try
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substitutedAst := substitutor.Execute(Node.Expression);
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finally
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substitutor.Free;
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end;
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// Step 2: Recursively expand any macros within the substituted expression.
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expandedAst := FExpander.ExpandNode(substitutedAst);
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// Step 3: Call the injected executor strategy to bind and evaluate the AST.
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value := FExecutor(expandedAst);
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// Step 4: Wrap the resulting value for insertion into the template.
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if value.Kind in [vkScalar, vkText] then
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Result := TDataValue.FromIntf<IAstNode>(TAst.Constant(value))
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else
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Result := value;
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end;
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function TExpansionHelper.VisitUnquoteSplicing(const Node: IUnquoteSplicingNode): TDataValue;
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var
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unquotedValue: TDataValue;
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unquotedNode: IAstNode;
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begin
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unquotedValue := Self.VisitUnquote(TAst.Unquote(Node.Expression));
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if unquotedValue.Kind = vkInterface then
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unquotedNode := unquotedValue.AsIntf<IAstNode>
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else
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unquotedNode := nil;
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if not (unquotedNode is TBlockExpressionNode) then
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raise Exception.Create('Expression inside unquote-splicing (`~@`) must evaluate to a list of nodes (a block).');
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Result := unquotedValue;
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end;
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{ TSubstitutor }
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constructor TSubstitutor.Create(AParamScope: IExecutionScope);
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begin
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inherited Create;
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FParamScope := AParamScope;
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end;
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function TSubstitutor.VisitIdentifier(const Node: IIdentifierNode): TDataValue;
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var
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addr: TResolvedAddress;
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nodeValue: TDataValue;
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begin
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addr := FParamScope.CreateDescriptor.FindSymbol(Node.Name);
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if (addr.Kind = akLocalOrParent) and (addr.ScopeDepth = 0) then
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begin
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nodeValue := FParamScope.Values[addr];
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Result := nodeValue;
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exit;
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end;
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Result := inherited VisitIdentifier(Node);
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end;
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end.
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