feat(oop): METHOD ... INLINE <expr> and MESSAGE handlers

Harbour's inline-method sugar was parsed but the body was skipped,
leaving any `METHOD X() INLINE expr` declaration registered in the
class vtable with no matching HB_<CLASS>_X function — link error
at build time.

Parser: MethodDecl gains an InlineBody Expr field. parseClassMethodDecl
captures the expression after INLINE instead of skipping to EOL.
New parseMessageDecl handles `MESSAGE <name> [(params)] INLINE expr`
and returns the same MethodDecl shape.

Codegen: emitClassDecl walks members a second time after the class
registration init block and emits emitInlineMethodBody for each
IsInline method — a Frame(nParams, 0) + emitExpr(InlineBody) +
RetValue function. curMethodClass is bound so ::super: inside an
inline body still resolves.

Tested (/tmp/test_inline.prg): all four patterns — bare INLINE,
MESSAGE INLINE, INLINE with params, INLINE reading ::field —
produce expected values.

FiveSql2 43/43, Harbour compat 56/56, Go test ALL PASS.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

compiler/ast/ast.go

@@ -177,6 +177,7 @@ type MethodDecl struct {
 	ClassName  string         // METHOD name CLASS classname (standalone)
 	Params     []*ParamDecl
 	IsInline   bool           // INLINE method
+	InlineBody Expr           // inline expression body — `RETURN <expr>` equivalent
 	IsSetGet   bool           // METHOD name(x) SETGET — getter if no arg, setter if arg
 	IsAccess   bool           // ACCESS name METHOD getterName
 	IsAssign   bool           // ASSIGN name METHOD setterName

compiler/gengo/gen_class.go

@@ -74,6 +74,18 @@ func (g *Generator) emitClassDecl(cls *ast.ClassDecl) {
 	g.writeln("}")
 	g.writeln("")
 
+	// Emit function bodies for INLINE methods — the class-body form
+	// `METHOD X() INLINE expr` / `MESSAGE X INLINE expr` carries its
+	// own body, unlike plain METHOD declarations which expect a
+	// standalone `METHOD X() CLASS Foo` implementation elsewhere.
+	for _, m := range cls.Members {
+		md, ok := m.(*ast.MethodDecl)
+		if !ok || !md.IsInline || md.InlineBody == nil {
+			continue
+		}
+		g.emitInlineMethodBody(className, md)
+	}
+
 	// Also need a constructor function: Person() returns new object
 	// This is called as Person():New(...)
 	g.writeln(fmt.Sprintf("func HB_%s_CTOR(t *hbrt.Thread) {", className))
@@ -89,6 +101,40 @@ func (g *Generator) emitClassDecl(cls *ast.ClassDecl) {
 	// Constructor symbol already added in Generate() symbol collection phase
 }
 
+// emitInlineMethodBody generates the HB_<CLASS>_<METHOD> function for
+// an INLINE-declared method: the body is the single expression parsed
+// after the INLINE keyword, evaluated and returned. Params bind to
+// locals 1..N so the inline expression can reference them.
+func (g *Generator) emitInlineMethodBody(className string, md *ast.MethodDecl) {
+	methodName := strings.ToUpper(md.Name)
+	goFuncName := fmt.Sprintf("HB_%s_%s", className, methodName)
+	nParams := len(md.Params)
+
+	g.writeln(fmt.Sprintf("func %s(t *hbrt.Thread) {", goFuncName))
+	g.indent++
+	g.writeln(fmt.Sprintf("t.Frame(%d, 0)", nParams))
+	g.writeln("defer t.EndProc()")
+
+	// Param name → local index map so the inline expr can reference them.
+	localMap := make(localMap)
+	for i, p := range md.Params {
+		localMap[strings.ToUpper(p.Name)] = i + 1
+	}
+	prevLocals := g.curLocals
+	prevCls := g.curMethodClass
+	g.curLocals = localMap
+	g.curMethodClass = className
+
+	g.emitExpr(md.InlineBody)
+	g.writeln("t.RetValue()")
+
+	g.curLocals = prevLocals
+	g.curMethodClass = prevCls
+	g.indent--
+	g.writeln("}")
+	g.writeln("")
+}
+
 // emitMethodDeclStandalone generates a standalone METHOD ... CLASS ... implementation.
 func (g *Generator) emitMethodDeclStandalone(md *ast.MethodDecl) {
 	if md.ClassName == "" {

compiler/parser/parser.go

@@ -610,8 +610,14 @@ func (p *Parser) parseClassDecl() *ast.ClassDecl {
 				} else {
 					p.skipToEndOfLine()
 				}
+			} else if upper == "MESSAGE" {
+				// MESSAGE <name> [(params)] INLINE <expr>
+				// Harbour sugar for an inline method. Emit as MethodDecl so
+				// emitClassDecl routes it through AddMethod and the inline
+				// body emitter generates the HB_<CLASS>_<NAME> function.
+				members = append(members, p.parseMessageDecl())
 			} else if upper == "ON" || upper == "OPERATOR" || upper == "DESTRUCTOR" ||
-				upper == "DELEGATE" || upper == "ERROR" || upper == "MESSAGE" ||
+				upper == "DELEGATE" || upper == "ERROR" ||
 				upper == "VIRTUAL" || upper == "DEFERRED" {
 				// ON ERROR, OPERATOR "+" ARG, DESTRUCTOR, DELEGATE — skip to EOL
 				p.skipToEndOfLine()
@@ -740,8 +746,17 @@ func (p *Parser) parseClassMethodDecl() *ast.MethodDecl {
 		p.skipToEndOfLine()
 	}
 
-	// Skip INLINE + rest of line (METHOD ... INLINE expr)
+	// INLINE expression — parse as the method body instead of skipping.
-	p.skipClassInline()
+	// Harbour semantics: `METHOD X() INLINE expr` is sugar for a method
+	// whose body is `RETURN expr`.
+	isInline := false
+	var inlineBody ast.Expr
+	if p.current.Kind == token.INLINE_KW ||
+		(p.current.Kind == token.IDENT && p.currentUpper() == "INLINE") {
+		p.advance() // consume INLINE
+		isInline = true
+		inlineBody = p.parseExpr()
+	}
 
 	p.expectEndOfStmt()
 
@@ -750,11 +765,55 @@ func (p *Parser) parseClassMethodDecl() *ast.MethodDecl {
 		Name:       name,
 		Params:     params,
 		IsSetGet:   isSetGet,
+		IsInline:   isInline,
+		InlineBody: inlineBody,
 		EndPos:     methodPos,
 	}
 }
 
-// skipClassInline skips INLINE keyword and the rest of the line (used in CLASS body)
+// parseMessageDecl parses `MESSAGE <name> [(params)] INLINE <expr>` in
+// a CLASS body and returns a MethodDecl. Harbour semantics: a MESSAGE
+// handler is invoked like a method and behaves identically — the form
+// exists mostly for readability of "this ident is really a message
+// handler, not a regular method". Without INLINE the handler is
+// declaration-only (the real body arrives as a separate
+// `METHOD <name>() CLASS X` implementation).
+func (p *Parser) parseMessageDecl() *ast.MethodDecl {
+	msgPos := p.current.Pos
+	p.advance() // MESSAGE
+
+	name := p.expectMethodName().Literal
+
+	var params []*ast.ParamDecl
+	if p.match(token.LPAREN) {
+		params = p.parseParamList()
+		p.expect(token.RPAREN)
+	}
+
+	isInline := false
+	var inlineBody ast.Expr
+	if p.current.Kind == token.INLINE_KW ||
+		(p.current.Kind == token.IDENT && p.currentUpper() == "INLINE") {
+		p.advance()
+		isInline = true
+		inlineBody = p.parseExpr()
+	}
+
+	p.expectEndOfStmt()
+
+	return &ast.MethodDecl{
+		MethodPos:  msgPos,
+		Name:       name,
+		Params:     params,
+		IsInline:   isInline,
+		InlineBody: inlineBody,
+		EndPos:     msgPos,
+	}
+}
+
+// skipClassInline skips INLINE keyword and the rest of the line.
+// Used by ACCESS/ASSIGN decls where inline body handling hasn't been
+// wired up yet (falls back to pre-INLINE-capture behaviour).
 func (p *Parser) skipClassInline() {
 	if p.current.Kind == token.INLINE_KW ||
 		(p.current.Kind == token.IDENT && p.currentUpper() == "INLINE") {