checker/cgen: interface smart casts

Author: medvednikov

vlib/v/checker/checker.v

@@ -2983,7 +2983,7 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) table.Type {
 				c.error('non-bool type `$typ_sym.source_name` used as if condition', branch.pos)
 			}
 		}
-		// smartcast sumtypes when using `is`
+		// smartcast sumtypes and interfaces when using `is`
 		if branch.cond is ast.InfixExpr {
 			infix := branch.cond as ast.InfixExpr
 			if infix.op == .key_is &&
@@ -2994,7 +2994,7 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) table.Type {
 				// Register shadow variable or `as` variable with actual type
 				if is_variable {
 					left_sym := c.table.get_type_symbol(infix.left_type)
-					if left_sym.kind == .sum_type && branch.left_as_name.len > 0 {
+					if left_sym.kind in [.sum_type, .interface_] && branch.left_as_name.len > 0 {
 						mut is_mut := false
 						mut scope := c.file.scope.innermost(branch.body_pos.pos)
 						if infix.left is ast.Ident as infix_left {

vlib/v/gen/cgen.v

@@ -1134,20 +1134,20 @@ fn (mut g Gen) expr_with_cast(expr ast.Expr, got_type, expected_type table.Type)
 			got_sym := g.table.get_type_symbol(got_type)
 			if expected_is_ptr && got_is_ptr {
 				exp_der_styp := g.typ(expected_deref_type)
-				g.write('/* sum type cast */ ($exp_styp) memdup(&($exp_der_styp){.obj = ')
+				g.write('/* sum type cast */ ($exp_styp) memdup(&($exp_der_styp){._object = ')
 				g.expr(expr)
 				g.write(', .typ = $got_idx /* $got_sym.name */}, sizeof($exp_der_styp))')
 			} else if expected_is_ptr {
 				exp_der_styp := g.typ(expected_deref_type)
-				g.write('/* sum type cast */ ($exp_styp) memdup(&($exp_der_styp){.obj = memdup(&($got_styp[]) {')
+				g.write('/* sum type cast */ ($exp_styp) memdup(&($exp_der_styp){._object = memdup(&($got_styp[]) {')
 				g.expr(expr)
 				g.write('}, sizeof($got_styp)), .typ = $got_idx /* $got_sym.name */}, sizeof($exp_der_styp))')
 			} else if got_is_ptr {
-				g.write('/* sum type cast */ ($exp_styp) {.obj = ')
+				g.write('/* sum type cast */ ($exp_styp) {._object = ')
 				g.expr(expr)
 				g.write(', .typ = $got_idx /* $got_sym.name */}')
 			} else {
-				g.write('/* sum type cast */ ($exp_styp) {.obj = memdup(&($got_styp[]) {')
+				g.write('/* sum type cast */ ($exp_styp) {._object = memdup(&($got_styp[]) {')
 				g.expr(expr)
 				g.write('}, sizeof($got_styp)), .typ = $got_idx /* $got_sym.name */}')
 			}
@@ -2604,7 +2604,7 @@ fn (mut g Gen) match_expr(node ast.MatchExpr) {
 					g.expr(node.cond)
 					dot_or_ptr := if node.cond_type.is_ptr() { '->' } else { '.' }
 					g.write(dot_or_ptr)
-					g.writeln('obj; // ST it')
+					g.writeln('_object; // ST it')
 					if node.var_name.len > 0 {
 						// for now we just copy it
 						g.writeln('\t$it_type* $node.var_name = it;')
@@ -2788,7 +2788,7 @@ fn (mut g Gen) if_expr(node ast.IfExpr) {
 			} else {
 				g.write('.')
 			}
-			g.writeln('obj;')
+			g.writeln('_object;')
 			g.writeln('\t$it_type* $branch.left_as_name = _sc_tmp_$branch.pos.pos;')
 		}
 		g.stmts(branch.stmts)
@@ -3773,7 +3773,7 @@ fn (mut g Gen) write_types(types []table.TypeSymbol) {
 					g.type_definitions.writeln('//          | ${sv:4d} = ${g.typ(sv):-20s}')
 				}
 				g.type_definitions.writeln('typedef struct {')
-				g.type_definitions.writeln('    void* obj;')
+				g.type_definitions.writeln('    void* _object;')
 				g.type_definitions.writeln('    int typ;')
 				g.type_definitions.writeln('} $name;')
 				g.type_definitions.writeln('')
@@ -4704,7 +4704,7 @@ fn (mut g Gen) as_cast(node ast.AsCast) {
 		g.write('/* as */ ($styp*)__as_cast(')
 		g.expr(node.expr)
 		g.write(dot)
-		g.write('obj, ')
+		g.write('_object, ')
 		g.expr(node.expr)
 		g.write(dot)
 		g.write('typ, /*expected:*/$node.typ)')

vlib/v/tests/interface_test.v

@@ -23,7 +23,7 @@ fn (c &Cat) speak(s string) {
 }
 
 fn (c Cat) name_detailed(pet_name string) string {
-	return '$pet_name the ${typeof(c)}, breed:${c.breed}'
+	return '$pet_name the ${typeof(c)}, breed:$c.breed'
 }
 
 fn (mut c Cat) set_breed(new string) {
@@ -46,7 +46,7 @@ fn (d Dog) name() string {
 }
 
 fn (d Dog) name_detailed(pet_name string) string {
-	return '$pet_name the ${typeof(d)}, breed:${d.breed}'
+	return '$pet_name the ${typeof(d)}, breed:$d.breed'
 }
 
 fn (mut d Dog) set_breed(new string) {
@@ -67,23 +67,25 @@ fn perform_speak(a Animal) {
 	assert name == 'Dog' || name == 'Cat'
 	if a is Dog {
 		assert name == 'Dog'
+		assert a.breed == 'Labrador Retriever' // test smart casting
+		println(a.breed)
 	}
 	println(a.name())
 	println('Got animal of type: ${typeof(a)}') // TODO: get implementation type (if possible)
-	// assert a is Dog || a is Cat // TODO: enable when available
+	assert a is Dog || a is Cat
 }
 
 fn perform_speak_on_ptr(a &Animal) {
 	a.speak('Hi !')
 	assert true
 	name := a.name()
 	assert name == 'Dog' || name == 'Cat'
-	// if a is Dog {
-	// assert name == 'Dog'
-	// }
+	if a is Dog {
+		assert name == 'Dog'
+	}
 	println(a.name())
 	println('Got animal of type: ${typeof(a)}') // TODO: get implementation type (if possible)
-	// assert a is Dog || a is Cat // TODO: enable when available
+	assert a is Dog || a is Cat
 }
 
 fn test_perform_speak() {