checker: default field fixes

vlib/v/checker/checker.v

@@ -365,13 +365,16 @@ pub fn (mut c Checker) struct_decl(decl ast.StructDecl) {
 					field.default_expr.position())
 			}
 			// Check for unnecessary inits like ` = 0` and ` = ''`
+			if field.typ.is_ptr() {
+				continue
+			}
 			if field.default_expr is ast.IntegerLiteral as x {
 				if x.val == '0' {
 					c.error('unnecessary default value of `0`: struct fields are zeroed by default',
 						field.pos)
 				}
 			} else if field.default_expr is ast.StringLiteral as x {
-				if x.val == "''" {
+				if x.val == '' {
 					c.error("unnecessary default value of '': struct fields are zeroed by default",
 						field.pos)
 				}

vlib/v/checker/tests/struct_unneeded_default.out

@@ -4,3 +4,10 @@ vlib/v/checker/tests/struct_unneeded_default.vv:2:2: error: unnecessary default
       |     ~~~~~~
     3 |     s string = ''
     4 | }
+vlib/v/checker/tests/struct_unneeded_default.vv:3:2: error: unnecessary default value of '': struct fields are zeroed by default
+    1 | struct Test {
+    2 |     n int = 0
+    3 |     s string = ''
+      |     ~~~~~~~~~
+    4 | }
+    5 |

vlib/v/tests/string_interpolation_of_array_of_structs_test.v

@@ -2,8 +2,8 @@ module main
 
 struct Anything {
 mut:
-	name  string = ''
-	keepo int = 0
+	name  string
+	keepo int
 }
 
 fn (a Anything) str() string {
@@ -34,8 +34,8 @@ fn test_array_of_ptrs_to_structs_can_be_printed() {
 // (note the str method defined on (a &T), instead on (a T))
 struct PstrAnything {
 mut:
-	name  string = ''
-	keepo int = 0
+	name  string
+	keepo int
 }
 
 fn (a &PstrAnything) str() string {
@@ -64,7 +64,7 @@ fn test_array_of_ptrs_to_structs_can_be_printed_when_structs_have_str_with_ptr()
 
 //
 fn test_stack_array_of_structs_can_be_printed_when_structs_have_ordinary_str() {
-	mut t := [3]Anything
+	mut t := [3]Anything{}
 	t[0] = Anything{
 		name: '012'
 	}
@@ -86,7 +86,7 @@ fn test_stack_array_of_structs_can_be_printed_when_structs_have_ordinary_str() {
 
 fn test_stack_array_of_structs_can_be_printed_when_structs_have_str_with_ptr() {
 	// this generates a C error
-	mut pt := [3]PstrAnything
+	mut pt := [3]PstrAnything{}
 	pt[0] = PstrAnything{
 		name: 'P012'
 	}