From 6fa8e4269e19a7330339cc98cb000530e42829f3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20D=C3=A4schle?= <daniel.daeschle@gmail.com>
Date: Fri, 30 Jul 2021 02:18:20 +0200
Subject: [PATCH] checker: force interface init (#10910)

---
 vlib/context/cancel.v                         |  1 +
 vlib/v/checker/checker.v                      | 10 +++++++++
 vlib/v/checker/tests/interface_init_err.out   |  6 +++++
 vlib/v/checker/tests/interface_init_err.vv    | 16 ++++++++++++++
 .../checker/tests/recursive_interface_err.out |  5 +++++
 .../checker/tests/recursive_interface_err.vv  |  3 +++
 vlib/v/gen/c/cgen.v                           |  4 ++++
 vlib/v/gen/native/amd64.v                     |  2 +-
 vlib/v/gen/native/arm64.v                     |  2 +-
 vlib/v/gen/native/gen.v                       | 21 ++++++++++--------
 vlib/v/gen/native/macho_test.v                |  1 +
 .../assign_to_interface_field_test.v          |  3 +--
 vlib/v/tests/interface_nested_field_test.v    | 22 ++++++++++++++-----
 vlib/v/tests/struct_ierror_test.v             | 10 +++++++++
 14 files changed, 87 insertions(+), 19 deletions(-)
 create mode 100644 vlib/v/checker/tests/interface_init_err.out
 create mode 100644 vlib/v/checker/tests/interface_init_err.vv
 create mode 100644 vlib/v/checker/tests/recursive_interface_err.out
 create mode 100644 vlib/v/checker/tests/recursive_interface_err.vv
 create mode 100644 vlib/v/tests/struct_ierror_test.v

diff --git a/vlib/context/cancel.v b/vlib/context/cancel.v
index 023b1a8e29..2972b17cc5 100644
--- a/vlib/context/cancel.v
+++ b/vlib/context/cancel.v
@@ -57,6 +57,7 @@ fn new_cancel_context(parent Context) &CancelContext {
 		context: parent
 		mutex: sync.new_mutex()
 		done: chan int{cap: 2}
+		err: none
 	}
 }
 
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 7aaf4fd3ec..343b13a7b8 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -540,6 +540,10 @@ pub fn (mut c Checker) interface_decl(mut decl ast.InterfaceDecl) {
 				c.check_valid_snake_case(field.name, 'field name', field.pos)
 			}
 			c.ensure_type_exists(field.typ, field.pos) or { return }
+			if field.typ == decl.typ {
+				c.error('recursive interface fields are not allowed because they cannot be initialised',
+					field.type_pos)
+			}
 			for j in 0 .. i {
 				if field.name == decl.fields[j].name {
 					c.error('field name `$field.name` duplicate', field.pos)
@@ -1154,6 +1158,12 @@ pub fn (mut c Checker) struct_init(mut node ast.StructInit) ast.Type {
 					c.error('reference field `${type_sym.name}.$field.name` must be initialized',
 						node.pos)
 				}
+				// Do not allow empty uninitialized interfaces
+				sym := c.table.get_type_symbol(field.typ)
+				if sym.kind == .interface_ {
+					c.error('interface field `${type_sym.name}.$field.name` must be initialized',
+						node.pos)
+				}
 				// Do not allow empty uninitialized sum types
 				/*
 				sym := c.table.get_type_symbol(field.typ)
diff --git a/vlib/v/checker/tests/interface_init_err.out b/vlib/v/checker/tests/interface_init_err.out
new file mode 100644
index 0000000000..238395c279
--- /dev/null
+++ b/vlib/v/checker/tests/interface_init_err.out
@@ -0,0 +1,6 @@
+vlib/v/checker/tests/interface_init_err.vv:15:7: error: interface field `Server.handler` must be initialized
+   13 | 
+   14 | fn main() {
+   15 |     _ := Server{}
+      |          ~~~~~~~~
+   16 | }
diff --git a/vlib/v/checker/tests/interface_init_err.vv b/vlib/v/checker/tests/interface_init_err.vv
new file mode 100644
index 0000000000..e2def73128
--- /dev/null
+++ b/vlib/v/checker/tests/interface_init_err.vv
@@ -0,0 +1,16 @@
+interface Handler {
+	foo string
+	handle(int) int
+}
+
+struct Server {
+	handler Handler
+}
+
+fn (s Server) handle(x int) int {
+	return x
+}
+
+fn main() {
+	_ := Server{}
+}
diff --git a/vlib/v/checker/tests/recursive_interface_err.out b/vlib/v/checker/tests/recursive_interface_err.out
new file mode 100644
index 0000000000..f3ec2a751a
--- /dev/null
+++ b/vlib/v/checker/tests/recursive_interface_err.out
@@ -0,0 +1,5 @@
+vlib/v/checker/tests/recursive_interface_err.vv:2:6: error: recursive interface fields are not allowed because they cannot be initialised
+    1 | interface Foo {
+    2 |     foo Foo
+      |         ~~~
+    3 | }
diff --git a/vlib/v/checker/tests/recursive_interface_err.vv b/vlib/v/checker/tests/recursive_interface_err.vv
new file mode 100644
index 0000000000..74a3dd9a50
--- /dev/null
+++ b/vlib/v/checker/tests/recursive_interface_err.vv
@@ -0,0 +1,3 @@
+interface Foo {
+	foo Foo
+}
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 8a8131eaa4..29cbd44296 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -1923,6 +1923,10 @@ fn (mut g Gen) expr_with_cast(expr ast.Expr, got_type_raw ast.Type, expected_typ
 		g.write('.msg))')
 		return
 	}
+	if got_sym.kind == .none_ && exp_sym.name == 'IError' {
+		g.expr(expr)
+		return
+	}
 	if exp_sym.info is ast.Interface && got_type_raw.idx() != expected_type.idx()
 		&& !expected_type.has_flag(.optional) {
 		if expr is ast.StructInit && !got_type.is_ptr() {
diff --git a/vlib/v/gen/native/amd64.v b/vlib/v/gen/native/amd64.v
index a568e5d79d..a690d0511c 100644
--- a/vlib/v/gen/native/amd64.v
+++ b/vlib/v/gen/native/amd64.v
@@ -5,7 +5,7 @@ import v.ast
 
 pub struct Amd64 {
 mut:
-	g &Gen
+	g Gen
 	// arm64 specific stuff for code generation
 }
 
diff --git a/vlib/v/gen/native/arm64.v b/vlib/v/gen/native/arm64.v
index c0fceece35..f4eb5aac12 100644
--- a/vlib/v/gen/native/arm64.v
+++ b/vlib/v/gen/native/arm64.v
@@ -24,7 +24,7 @@ enum Arm64Register {
 
 pub struct Arm64 {
 mut:
-	g &Gen
+	g Gen
 	// arm64 specific stuff for code generation
 }
 
diff --git a/vlib/v/gen/native/gen.v b/vlib/v/gen/native/gen.v
index 9695e4966b..8df68a923d 100644
--- a/vlib/v/gen/native/gen.v
+++ b/vlib/v/gen/native/gen.v
@@ -15,7 +15,8 @@ import term
 pub const builtins = ['println', 'exit']
 
 interface CodeGen {
-	g &Gen
+mut:
+	g Gen
 	gen_exit(mut g Gen, expr ast.Expr)
 	// XXX WHY gen_exit fn (expr ast.Expr)
 }
@@ -54,13 +55,13 @@ enum Size {
 	_64
 }
 
-fn (g &Gen) get_backend() ?CodeGen {
-	match g.pref.arch {
+fn get_backend(arch pref.Arch) ?CodeGen {
+	match arch {
 		.arm64 {
-			return Arm64{g}
+			return Arm64{}
 		}
 		.amd64 {
-			return Amd64{g}
+			return Amd64{}
 		}
 		else {}
 	}
@@ -73,11 +74,13 @@ pub fn gen(files []&ast.File, table &ast.Table, out_name string, pref &pref.Pref
 		sect_header_name_pos: 0
 		out_name: out_name
 		pref: pref
+		// TODO: workaround, needs to support recursive init
+		cgen: get_backend(pref.arch) or {
+			eprintln('No available backend for this configuration. Use `-a arm64` or `-a amd64`.')
+			exit(1)
+		}
 	}
-	g.cgen = g.get_backend() or {
-		eprintln('No available backend for this configuration. Use `-a arm64` or `-a amd64`.')
-		exit(1)
-	}
+	g.cgen.g = g
 	g.generate_header()
 	for file in files {
 		if file.warnings.len > 0 {
diff --git a/vlib/v/gen/native/macho_test.v b/vlib/v/gen/native/macho_test.v
index 8035e4c597..9da074d71d 100644
--- a/vlib/v/gen/native/macho_test.v
+++ b/vlib/v/gen/native/macho_test.v
@@ -9,6 +9,7 @@ fn test_macho() {
 		pref: &pref.Preferences{}
 		out_name: 'test.bin'
 		table: ast.new_table()
+		cgen: native.Amd64{}
 	}
 	g.generate_macho_header()
 	g.generate_macho_footer()
diff --git a/vlib/v/tests/interface_edge_cases/assign_to_interface_field_test.v b/vlib/v/tests/interface_edge_cases/assign_to_interface_field_test.v
index cb69e550c8..9f279bafaa 100644
--- a/vlib/v/tests/interface_edge_cases/assign_to_interface_field_test.v
+++ b/vlib/v/tests/interface_edge_cases/assign_to_interface_field_test.v
@@ -20,8 +20,7 @@ mut:
 }
 
 fn test_a_struct_implementing_an_interface_can_be_assigned_without_explicit_casts() {
-	mut anyplanet := AnyPlanet{}
-	anyplanet.planet = Moon{}
+	mut anyplanet := AnyPlanet{Moon{}}
 	assert anyplanet.planet.name() == 'moon'
 	anyplanet.planet = Mars{}
 	assert anyplanet.planet.name() == 'mars'
diff --git a/vlib/v/tests/interface_nested_field_test.v b/vlib/v/tests/interface_nested_field_test.v
index 606df66f52..7577bcb89d 100644
--- a/vlib/v/tests/interface_nested_field_test.v
+++ b/vlib/v/tests/interface_nested_field_test.v
@@ -2,20 +2,30 @@ struct Base {
 }
 
 interface Foo {
-	parent Foo
+	parent Foo2
+	thing(mut b Base, value i64) string
+}
+
+interface Foo2 {
 	thing(mut b Base, value i64) string
 }
 
 struct Bar {
-	parent Foo
+	parent Foo2
 }
 
+struct Bar2 {}
+
 fn (f Bar) thing(mut b Base, value i64) string {
 	return 'bar'
 }
 
+fn (f Bar2) thing(mut b Base, value i64) string {
+	return 'bar2'
+}
+
 struct SubBar {
-	parent Foo = Bar{}
+	parent Foo2 = Bar2{}
 }
 
 fn (f SubBar) thing(mut b Base, value i64) string {
@@ -23,8 +33,8 @@ fn (f SubBar) thing(mut b Base, value i64) string {
 }
 
 fn test_interface_nested_field() {
-	mut foo_group := []Foo{}
-	foo_group << Bar{}
+	mut foo_group := []Foo2{}
+	foo_group << Bar2{}
 	foo_group << SubBar{}
 
 	mut b := Base{}
@@ -34,7 +44,7 @@ fn test_interface_nested_field() {
 		ret << foo.thing(mut b, 22)
 	}
 	assert ret.len == 2
-	assert ret[0] == 'bar'
+	assert ret[0] == 'bar2'
 	assert ret[1] == 'subbar'
 }
 
diff --git a/vlib/v/tests/struct_ierror_test.v b/vlib/v/tests/struct_ierror_test.v
new file mode 100644
index 0000000000..af1303380d
--- /dev/null
+++ b/vlib/v/tests/struct_ierror_test.v
@@ -0,0 +1,10 @@
+struct Test {
+	err IError
+}
+
+fn test_init_with_none() {
+	t := Test{
+		err: none
+	}
+	// compiles successfully
+}