checker: add error for `fn f() Struct { return &Struct{} }` (#6019)

examples/eventbus/modules/some_module/some_module.v

@@ -30,5 +30,5 @@ pub fn do_work(){
 }
 
 pub fn get_subscriber() eventbus.Subscriber {
-	return eb.subscriber
+	return *eb.subscriber
 }

vlib/math/unsafe.v

@@ -6,7 +6,7 @@ module math
 // with the sign bit of f and the result in the same bit position.
 // f32_bits(f32_from_bits(x)) == x.
 pub fn f32_bits(f f32) u32 {
-	p := &u32(&f)
+	p := *(&u32(&f))
 	return p
 }
 
@@ -15,7 +15,7 @@ pub fn f32_bits(f f32) u32 {
 // and the result in the same bit position.
 // f32_from_bits(f32_bits(x)) == x.
 pub fn f32_from_bits(b u32) f32 {
-	p := &f32(&b)
+	p := *(&f32(&b))
 	return p
 }
 
@@ -23,7 +23,7 @@ pub fn f32_from_bits(b u32) f32 {
 // with the sign bit of f and the result in the same bit position,
 // and f64_bits(f64_from_bits(x)) == x.
 pub fn f64_bits(f f64) u64 {
-	p := &u64(&f)
+	p := *(&u64(&f))
 	return p
 }
 
@@ -32,7 +32,7 @@ pub fn f64_bits(f f64) u64 {
 // and the result in the same bit position.
 // f64_from_bits(f64_bits(x)) == x.
 pub fn f64_from_bits(b u64) f64 {
-	p := &f64(&b)
+	p := *(&f64(&b))
 	return p
 }
 

vlib/rand/mt19937/mt19937.v

@@ -72,7 +72,7 @@ fn calculate_state(seed_data []u32, mut state []u64) []u64 {
 	for j := 1; j < nn; j++ {
 		state[j] = u64(6364136223846793005) * (state[j - 1] ^ (state[j - 1] >> 62)) + u64(j)
 	}
-	return state
+	return *state
 }
 
 // seed() - Set the seed, needs only two u32s in little endian format as [lower, higher]

vlib/sokol/gfx/gfx_structs.v

@@ -165,7 +165,7 @@ pub mut:
 pub fn (mut desc C.sg_shader_stage_desc) set_image(index int, name string) C.sg_shader_stage_desc {
     desc.images[index].name = name.str
     desc.images[index].@type = ._2d
-    return desc
+    return *desc
 }
 
 

vlib/sync/pool.v

@@ -164,7 +164,7 @@ fn process_in_thread(mut pool PoolProcessor, task_id int) {
 pub fn (pool &PoolProcessor) get_string_item(idx int) string {
    // return *(&string(pool.items[idx]))
    // TODO: the below is a hack, remove it when v2 casting works again
-   return &string( pool.items[idx] )
+   return *(&string( pool.items[idx] ))
 }
 
 // get_int_item - called by the worker callback.

vlib/v/ast/ast.v

@@ -400,7 +400,7 @@ pub mut:
 pub fn (i &Ident) var_info() IdentVar {
 	match i.info as info {
 		IdentVar {
-			return info
+			return *info
 		}
 		else {
 			// return IdentVar{}

vlib/v/checker/checker.v

@@ -1515,6 +1515,11 @@ pub fn (mut c Checker) return_stmt(mut return_stmt ast.Return) {
 			c.error('cannot use `$got_typ_sym.name` as type `$exp_typ_sym.name` in return argument',
 				pos)
 		}
+		if got_typ.is_ptr() && !exp_type.is_ptr() {
+			pos := return_stmt.exprs[i].position()
+			c.error('fn `$c.cur_fn.name` expects you to return a non reference type `${c.table.type_to_str(exp_type)}`, but you are returning `${c.table.type_to_str(got_typ)}` instead',
+				pos)
+		}
 	}
 }
 
@@ -1905,7 +1910,7 @@ fn const_int_value(cfield ast.ConstField) ?int {
 
 fn is_const_integer(cfield ast.ConstField) ?ast.IntegerLiteral {
 	match cfield.expr {
-		ast.IntegerLiteral { return it }
+		ast.IntegerLiteral { return *it }
 		else {}
 	}
 	return none

vlib/v/checker/tests/return_ref_as_no_ref_bug.out

@@ -0,0 +1,7 @@
+vlib/v/checker/tests/return_ref_as_no_ref_bug.v:11:9: error: fn `return_not_reference` expects you to return a non reference type `BugStruct`, but you are returning `&BugStruct` instead
+    9 | 
+   10 | fn return_not_reference() BugStruct{
+   11 |     return &BugStruct {
+      |            ^
+   12 |         id: 1
+   13 |     }

vlib/v/checker/tests/return_ref_as_no_ref_bug.vv

@@ -0,0 +1,14 @@
+struct BugStruct {
+	id	int
+}
+
+fn main() {
+	x := return_not_reference()
+	println(x.id)
+}
+
+fn return_not_reference() BugStruct{
+	return &BugStruct {
+		id: 1
+	}
+}

vlib/v/doc/doc.v

@@ -431,7 +431,7 @@ fn (mut d Doc) generate() ?Doc {
 	d.time_generated = time.now()
 	d.contents.sort_by_name()
 	d.contents.sort_by_category()
-	return d
+	return *d
 }
 
 pub fn generate(input_path string, pub_only, with_comments bool) ?Doc {

vlib/v/table/atypes.v

@@ -362,7 +362,7 @@ pub fn (t &TypeSymbol) str() string {
 [inline]
 pub fn (t &TypeSymbol) enum_info() Enum {
 	match t.info {
-		Enum { return it }
+		Enum { return *it }
 		else { panic('TypeSymbol.enum_info(): no enum info for type: $t.name') }
 	}
 }
@@ -370,7 +370,7 @@ pub fn (t &TypeSymbol) enum_info() Enum {
 [inline]
 pub fn (t &TypeSymbol) mr_info() MultiReturn {
 	match t.info {
-		MultiReturn { return it }
+		MultiReturn { return *it }
 		else { panic('TypeSymbol.mr_info(): no multi return info for type: $t.name') }
 	}
 }
@@ -378,7 +378,7 @@ pub fn (t &TypeSymbol) mr_info() MultiReturn {
 [inline]
 pub fn (t &TypeSymbol) array_info() Array {
 	match t.info {
-		Array { return it }
+		Array { return *it }
 		else { panic('TypeSymbol.array_info(): no array info for type: $t.name') }
 	}
 }
@@ -386,7 +386,7 @@ pub fn (t &TypeSymbol) array_info() Array {
 [inline]
 pub fn (t &TypeSymbol) array_fixed_info() ArrayFixed {
 	match t.info {
-		ArrayFixed { return it }
+		ArrayFixed { return *it }
 		else { panic('TypeSymbol.array_fixed(): no array fixed info for type: $t.name') }
 	}
 }
@@ -394,7 +394,7 @@ pub fn (t &TypeSymbol) array_fixed_info() ArrayFixed {
 [inline]
 pub fn (t &TypeSymbol) map_info() Map {
 	match t.info {
-		Map { return it }
+		Map { return *it }
 		else { panic('TypeSymbol.map_info(): no map info for type: $t.name') }
 	}
 }
@@ -402,7 +402,7 @@ pub fn (t &TypeSymbol) map_info() Map {
 [inline]
 pub fn (t &TypeSymbol) struct_info() Struct {
 	match t.info {
-		Struct { return it }
+		Struct { return *it }
 		else { panic('TypeSymbol.struct_info(): no struct info for type: $t.name') }
 	}
 }

vlib/v/tests/generics_test.v

@@ -70,7 +70,7 @@ fn mut_arg<T>(mut x T) {
 
 fn mut_arg2<T>(mut x T) T {
 	println(x.name) // = 'foo'
-	return x
+	return *x
 }
 
 fn test_create() {