node: support magic __FILE__, __LINE__ etc constants

fixtures/0011-magic-consts.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace myNamespace;
+
+echo __file__;
+
+echo __Line__;
+
+echo __DIR__;
+
+echo __NAMESPACE__;
+
+function Foo() {
+	echo __FUNCTION__;
+}
+
+class Bar {
+	function Baz() {
+		echo __CLASS__ . "::" . __METHOD__	;
+		echo Baz::class;
+	}
+}
+
+// TODO __TRAIT__

node.go

@@ -39,6 +39,10 @@ type conversionState struct {
 	currentClassName       string
 	currentClassParentName string
 	currentErrHandler      string
+	currentFunctionName    string
+	currentMethodName      string
+	currentNamespace       string
+	currentTraitName       string // TODO
 	importPackages         map[string]struct{}
 }
 
@@ -125,6 +129,7 @@ func (this *conversionState) convertNoFreeFloating(n_ node.Node) (string, error)
 					return "", err
 				}
 				packageName = namespace
+				this.currentNamespace = packageName
 
 			default:
 				this.currentErrHandler = "panic(err)\n" // top-level init/main behaviour
@@ -273,6 +278,9 @@ func (this *conversionState) convertNoFreeFloating(n_ node.Node) (string, error)
 					return "", parseErr{s, err}
 				}
 
+				prevMethodName := this.currentMethodName
+				this.currentMethodName = funcName
+
 				// TODO implement abstract methods as method functions
 
 				// Doc comment
@@ -322,6 +330,9 @@ func (this *conversionState) convertNoFreeFloating(n_ node.Node) (string, error)
 
 				}
 
+				// Reinstate stack
+				this.currentMethodName = prevMethodName
+
 			default:
 				return "", parseErr{s, fmt.Errorf("Class '%s' contained unexpected AST node; expected PropertyList / ClassMethod", className)}
 			}
@@ -407,11 +418,18 @@ func (this *conversionState) convertNoFreeFloating(n_ node.Node) (string, error)
 		funcName = toPublic(funcName)
 
 		// Convert body
+		prevFuncName := this.currentFunctionName
+		this.currentFunctionName = funcName
+
 		funcStmt, err := this.convertFunctionCommon(n.Params, n.ReturnType, n.ReturnsRef, n.Stmts)
 		if err != nil {
+			// FIXME an early-return will trash the `this` state around currentFunctionName, etc
+			// That's OK for now since we don't practically have any error handling than an unmitigated panic
 			return "", parseErr{n, err}
 		}
 
+		this.currentFunctionName = prevFuncName
+
 		ret := "func " + funcName + funcStmt + "\n"
 		return ret, nil
 
@@ -1188,6 +1206,50 @@ func (this *conversionState) convertNoFreeFloating(n_ node.Node) (string, error)
 
 		return strconv.Quote(rawValue), nil // Go source code quoting format
 
+	case *scalar.MagicConstant:
+		// magic constants are case-insensitive
+		switch strings.ToLower(n.Value) {
+		case `__file__`, `__dir__`:
+			// These are normally used in PHP for finding the absolute webroot directory (e.g. dirname(__FILE__) in index.php)
+			// The letter of the law would be to replace them with the *.go file/dir
+			// We could even emit a runtime call to get the Go file/line: @ref https://github.com/golang/go/issues/12876#issuecomment-146878684
+			// But in practice, the current working directory might be preferable
+			return `""`, nil
+
+		case `__line__`:
+			return fmt.Sprintf("%d", n.Position.StartLine), nil
+
+		case `__namespace__`:
+			return this.currentNamespace, nil
+
+		case `__function__`:
+			if this.currentFunctionName == "" {
+				return "", parseErr{n, fmt.Errorf("use of __FUNCTION__ outside of a function")}
+			}
+			return this.currentFunctionName, nil
+
+		case `__class__`:
+			if this.currentClassName == "" {
+				return "", parseErr{n, fmt.Errorf("use of __CLASS__ outside of a class")}
+			}
+			return this.currentClassName, nil
+
+		case `__method__`:
+			if this.currentMethodName == "" {
+				return "", parseErr{n, fmt.Errorf("use of __METHOD__ outside of a class method")}
+			}
+			return this.currentMethodName, nil
+
+		case `__trait__`:
+			if this.currentTraitName == "" {
+				return "", parseErr{n, fmt.Errorf("use of __TRAIT__ outside of a trait")}
+			}
+			return this.currentTraitName, nil
+
+		default:
+			return "", parseErr{n, fmt.Errorf("unrecognized magic constant '%s'", n.Value)}
+		}
+
 	//
 	//
 	//