node: initial try/catch support, track the error handler (WIP)

fixtures/0008-try-catch-finally.php

@@ -0,0 +1,16 @@
+<?php
+
+function Foo(): int {
+	throw new \Exception('error');
+	return 0;
+}
+
+try {
+	echo Foo();
+} catch (\BarException | \BazException $e) {
+	echo "bar or baz exception " . $e->getMessage() . "\n";
+} catch (\Exception $e) {
+	echo "other exception " . $e->getMessage() . "\n";
+} finally {
+	echo "finally";	
+}

node.go

@@ -38,6 +38,7 @@ func (pe parseErr) Unwrap() error {
 type conversionState struct {
 	currentClassName       string
 	currentClassParentName string
+	currentErrHandler      string
 }
 
 //
@@ -100,6 +101,15 @@ func (this *conversionState) convertNoFreeFloating(n_ node.Node) (string, error)
 		statements := []string{}
 
 		for _, s := range n.Stmts {
+
+			switch s.(type) {
+			case *stmt.Class, *stmt.Function, *stmt.Interface:
+				this.currentErrHandler = "return nil, err\n"
+
+			default:
+				this.currentErrHandler = "panic(err)\n" // top-level init/main behaviour
+			}
+
 			sm, err := this.convert(s)
 			if err != nil {
 				return "", parseErr{s, err}
@@ -511,7 +521,7 @@ func (this *conversionState) convertNoFreeFloating(n_ node.Node) (string, error)
 				// super() is a reserved name in PHP anyway
 				ret := "super, err := " + constructorName(this.currentClassParentName) + funcArgs + "\n"
 				ret += "if err != nil {\n"
-				ret += "return err\n"
+				ret += this.currentErrHandler //"return err\n"
 				ret += "}\n"
 				ret += "this." + this.currentClassParentName + " = *super // copy by value\n"
 				return ret, nil
@@ -611,6 +621,76 @@ func (this *conversionState) convertNoFreeFloating(n_ node.Node) (string, error)
 
 		return ret, nil
 
+	case *stmt.Try:
+
+		// Generate an if err != nil {} block that we can bring up whenever
+		// an error is raised in a body function call
+		// TODO This will produce shadowed error handlers - need to make sure we
+		// use err2, err3 etc based on our current level of nesting
+
+		// TODO put finally() code somewhere (before/after err checking??)
+
+		handler := ""
+		if len(n.Catches) == 0 {
+			handler = "// suppress error"
+		} else {
+
+			catchVars := ""
+			catchIfs := []string{}
+
+			for _, catch_ := range n.Catches {
+				catch, ok := catch_.(*stmt.Catch)
+				if !ok {
+					return "", parseErr{n, fmt.Errorf("expected stmt.Catch")}
+				}
+
+				catchVar := catch.Variable.(*expr.Variable).VarName.(*node.Identifier).Value
+
+				catchBody, err := this.convert(stmt.NewStmtList(catch.Stmts))
+				if err != nil {
+					return "", parseErr{catch_, err}
+				}
+
+				for _, typename_ := range catch.Types {
+					typename, err := this.resolveName(typename_)
+					if !ok {
+						return "", parseErr{catch_, err}
+					}
+
+					tempCatchVar := catchVar
+					if len(catch.Types) > 1 {
+						tempCatchVar += "_" + typename
+					}
+
+					catchVars += "var " + tempCatchVar + "*" + typename + "\n"
+
+					catchStmt := "if errors.As(err, &" + tempCatchVar + ") {\n"
+					if len(catch.Types) > 1 {
+						catchStmt += catchVar + " := " + tempCatchVar + " // rename\n"
+					}
+					catchStmt += catchBody // contains its own {}
+					catchStmt += "} "      // but without trailing NL
+
+					catchIfs = append(catchIfs, catchStmt)
+				}
+			}
+
+			handler = catchVars + strings.Join(catchIfs, "else") + "\n"
+		}
+
+		// Store the handler to be used going forwards
+		previousErrHandler := this.currentErrHandler
+		this.currentErrHandler = handler
+
+		body, err := this.convert(stmt.NewStmtList(n.Stmts))
+		if err != nil {
+			return "", parseErr{n, err}
+		}
+
+		// Reinstate parent error handler
+		this.currentErrHandler = previousErrHandler
+		return body, nil // Try/catch behaviour is transparently encoded in err handlers
+
 	case *stmt.Nop:
 		return "", nil
 
@@ -670,6 +750,8 @@ func (this *conversionState) convertNoFreeFloating(n_ node.Node) (string, error)
 			return "", parseErr{n, err}
 		}
 
+		// FIXME need to support `this.currentErrHandler`
+
 		return funcName + callParams, nil // expr only, no semicolon/newline
 
 	case *expr.StaticCall:
@@ -697,6 +779,8 @@ func (this *conversionState) convertNoFreeFloating(n_ node.Node) (string, error)
 			return "", parseErr{n, err}
 		}
 
+		// FIXME need to support `this.currentErrHandler`
+
 		return callTarget + callParams, nil // expr only, no semicolon/newline
 
 	case *expr.New:
@@ -750,6 +834,8 @@ func (this *conversionState) convertNoFreeFloating(n_ node.Node) (string, error)
 			return "", parseErr{n, err}
 		}
 
+		// FIXME need to support `this.currentErrHandler`
+
 		return parent + "." + child + args, nil
 
 	case *expr.PropertyFetch:
@@ -1021,11 +1107,25 @@ func (this *conversionState) resolveName(n node.Node) (string, error) {
 	// TODO support namespace lookups
 
 	paramType := unknownVarType
-	if vt, ok := n.(*name.Name); ok {
+	if n == nil || n == node.Node(nil) {
-		if len(vt.Parts) != 1 {
+		return paramType, nil
-			return "", parseErr{n, fmt.Errorf("name has %d parts, expected 1", len(vt.Parts))}
+	}
+
+	switch n := n.(type) {
+	case *name.FullyQualified:
+		if len(n.Parts) != 1 {
+			return "", parseErr{n, fmt.Errorf("name has %d parts, expected 1", len(n.Parts))}
 		}
-		paramType = vt.Parts[0].(*name.NamePart).Value
+		paramType = n.Parts[0].(*name.NamePart).Value
+
+	case *name.Name:
+		if len(n.Parts) != 1 {
+			return "", parseErr{n, fmt.Errorf("name has %d parts, expected 1", len(n.Parts))}
+		}
+		paramType = n.Parts[0].(*name.NamePart).Value
+
+	default:
+		return "", fmt.Errorf("unexpected name type %#v", n)
 	}
 
 	// Handle class lookups