Merge pull request #1101 from nspcc-dev/feature/convert

Support type conversions

pkg/compiler/codegen.go

@@ -708,6 +708,7 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 			name      string
 			numArgs   = len(n.Args)
 			isBuiltin bool
+			isFunc    bool
 		)
 
 		switch fun := n.Fun.(type) {
@@ -717,6 +718,10 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 			if !ok && !isBuiltin {
 				name = fun.Name
 			}
+			// distinguish lambda invocations from type conversions
+			if fun.Obj != nil && fun.Obj.Kind == ast.Var {
+				isFunc = true
+			}
 		case *ast.SelectorExpr:
 			// If this is a method call we need to walk the AST to load the struct locally.
 			// Otherwise this is a function call from a imported package and we can call it
@@ -763,9 +768,15 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 			// We can be sure builtins are of type *ast.Ident.
 			c.convertBuiltin(n)
 		case name != "":
-			// Function was not found thus is can be only an invocation of func-typed variable.
-			c.emitLoadVar(name)
-			emit.Opcode(c.prog.BinWriter, opcode.CALLA)
+			// Function was not found thus is can be only an invocation of func-typed variable or type conversion.
+			// We care only about string conversions because all others are effectively no-op in NeoVM.
+			// E.g. one cannot write `bool(int(a))`, only `int32(int(a))`.
+			if isString(c.typeOf(n.Fun)) {
+				c.emitConvert(stackitem.ByteArrayT)
+			} else if isFunc {
+				c.emitLoadVar(name)
+				emit.Opcode(c.prog.BinWriter, opcode.CALLA)
+			}
 		case isSyscall(f):
 			c.convertSyscall(n, f.selector.Name, f.name)
 		default:
@@ -987,6 +998,8 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 	// not the assertion type.
 	case *ast.TypeAssertExpr:
 		ast.Walk(c, n.X)
+		typ := toNeoType(c.typeOf(n.Type))
+		emit.Instruction(c.prog.BinWriter, opcode.CONVERT, []byte{byte(typ)})
 		return nil
 	}
 	return c