checker: fix warning & allow assigning to a union field without unsafe (#7970)

vlib/strconv/atof.v

@@ -522,7 +522,6 @@ pub fn atof64(s string) f64 {
 
 	res_parsing,pn = parser(s + ' ') // TODO: need an extra char for now
 	// println(pn)
-	unsafe {
 	match res_parsing {
 		parser_ok {
 			res.u = converter(mut pn)
@@ -542,6 +541,5 @@ pub fn atof64(s string) f64 {
 		else {
 		}
 	}
-	return res.f
-	}
+	return unsafe {res.f}
 }

vlib/strconv/atofq.v

@@ -37,7 +37,6 @@ pub fn atof_quick(s string) f64 {
 			i++
 		}
 	}
-	unsafe {
 	// infinite
 	if s[i] == `i` && i + 2 < s.len && s[i + 1] == `n` && s[i + 2] == `f` {
 		if sign > 0.0 {
@@ -46,7 +45,7 @@ pub fn atof_quick(s string) f64 {
 		else {
 			f.u = double_minus_infinity
 		}
-		return f.f
+		return unsafe {f.f}
 	}
 	// skip zeros
 	for i < s.len && s[i] == `0` {
@@ -59,7 +58,7 @@ pub fn atof_quick(s string) f64 {
 			else {
 				f.u = double_minus_zero
 			}
-			return f.f
+			return unsafe {f.f}
 		}
 	}
 	// integer part
@@ -110,11 +109,11 @@ pub fn atof_quick(s string) f64 {
 				else {
 					f.u = double_minus_infinity
 				}
-				return f.f
+				return unsafe {f.f}
 			}
 			tmp_mul := Float64u{u: pos_exp[exp]}
 			// C.printf("exp: %d  [0x%016llx] %f,",exp,pos_exp[exp],tmp_mul)
-			f.f = f.f * tmp_mul.f
+			f.f = unsafe {f.f * tmp_mul.f}
 		}
 		else {
 			if exp > neg_exp.len {
@@ -124,14 +123,15 @@ pub fn atof_quick(s string) f64 {
 				else {
 					f.u = double_minus_zero
 				}
-				return f.f
+				return unsafe {f.f}
 			}
 			tmp_mul := Float64u{u: neg_exp[exp]}
 
 			// C.printf("exp: %d  [0x%016llx] %f,",exp,pos_exp[exp],tmp_mul)
-			f.f = f.f * tmp_mul.f
+			f.f = unsafe {f.f * tmp_mul.f}
 		}
 	}
+	unsafe {
 		f.f = f.f * sign
 		return f.f
 	}

vlib/strconv/f32_f64_to_string_test.v

@@ -22,14 +22,14 @@ fn f64_from_bits1(b u64) f64 {
 	mut x := Ufloat64{}
 	x.b = b
 	//C.printf("bin: %016llx\n",x.f)
-	return x.f
+	return unsafe {x.f}
 }
 
 fn f32_from_bits1(b u32) f32 {
 	mut x := Ufloat32{}
 	x.b = b
 	//C.printf("bin: %08x\n",x.f)
-	return x.f
+	return unsafe {x.f}
 }
 
 fn test_float_to_str() {

vlib/strconv/f32_str.v

@@ -321,7 +321,7 @@ pub fn f32_to_decimal(mant u32, exp u32) Dec32 {
 // f32_to_str return a string in scientific notation with max n_digit after the dot
 pub fn f32_to_str(f f32, n_digit int) string {
 	mut u1 := Uf32{}
-	unsafe { u1.f = f }
+	u1.f = f
 	u := unsafe {u1.u}
 
 	neg   := (u>>(mantbits32+expbits32)) != 0
@@ -348,7 +348,7 @@ pub fn f32_to_str(f f32, n_digit int) string {
 // f32_to_str return a string in scientific notation with max n_digit after the dot
 pub fn f32_to_str_pad(f f32, n_digit int) string {
 	mut u1 := Uf32{}
-	unsafe { u1.f = f }
+	u1.f = f
 	u := unsafe {u1.u}
 
 	neg   := (u>>(mantbits32+expbits32)) != 0

vlib/strconv/f64_str.v

@@ -370,7 +370,7 @@ fn f64_to_decimal(mant u64, exp u64) Dec64 {
 // f64_to_str return a string in scientific notation with max n_digit after the dot
 pub fn f64_to_str(f f64, n_digit int) string {
 	mut u1 := Uf64{}
-	unsafe { u1.f = f }
+	u1.f = f
 	u := unsafe {u1.u}
 
 	neg   := (u>>(mantbits64+expbits64)) != 0
@@ -395,7 +395,7 @@ pub fn f64_to_str(f f64, n_digit int) string {
 // f64_to_str return a string in scientific notation with max n_digit after the dot
 pub fn f64_to_str_pad(f f64, n_digit int) string {
 	mut u1 := Uf64{}
-	unsafe { u1.f = f }
+	u1.f = f
 	u := unsafe {u1.u}
 
 	neg   := (u>>(mantbits64+expbits64)) != 0

vlib/v/ast/ast.v

@@ -108,6 +108,7 @@ pub:
 	field_name      string
 	is_mut          bool // is used for the case `if mut ident.selector is MyType {`, it indicates if the root ident is mutable
 	mut_pos         token.Position
+	next_token      token.Kind
 pub mut:
 	expr_type       table.Type // type of `Foo` in `Foo.bar`
 	typ             table.Type // type of the entire thing (`Foo.bar`)

vlib/v/checker/checker.v

@@ -1062,9 +1062,6 @@ fn (mut c Checker) fail_if_immutable(expr ast.Expr) (string, token.Position) {
 						// No automatic lock for struct access
 						explicit_lock_needed = true
 					}
-					if struct_info.is_union && !c.inside_unsafe {
-						c.warn('accessing union fields requires `unsafe`', expr.pos)
-					}
 				}
 				.array, .string {
 					// This should only happen in `builtin`
@@ -2028,6 +2025,7 @@ pub fn (mut c Checker) selector_expr(mut selector_expr ast.SelectorExpr) table.T
 			has_field = true
 			field = f
 		} else {
+			// look for embedded field
 			if sym.info is table.Struct {
 				mut found_fields := []table.Field{}
 				mut embed_of_found_fields := []table.Type{}
@@ -2050,6 +2048,14 @@ pub fn (mut c Checker) selector_expr(mut selector_expr ast.SelectorExpr) table.T
 				unknown_field_msg = err
 			}
 		}
+		if !c.inside_unsafe {
+			if sym.info is table.Struct {
+				if sym.info.is_union && selector_expr.next_token !in token.assign_tokens {
+					c.warn('reading a union field (or its address) requires `unsafe`',
+						selector_expr.pos)
+				}
+			}
+		}
 	}
 	if has_field {
 		if sym.mod != c.mod && !field.is_pub && sym.language != .c {

vlib/v/checker/tests/union_unsafe_fields.out

@@ -0,0 +1,13 @@
+vlib/v/checker/tests/union_unsafe_fields.vv:10:9: error: reading a union field (or its address) requires `unsafe`
+    8 |     mut u := Uf32{u: 3}
+    9 |     u.f = 3.3 // ok
+   10 |     _ := u.u
+      |            ^
+   11 |     return &u.f
+   12 | }
+vlib/v/checker/tests/union_unsafe_fields.vv:11:12: error: reading a union field (or its address) requires `unsafe`
+    9 |     u.f = 3.3 // ok
+   10 |     _ := u.u
+   11 |     return &u.f
+      |               ^
+   12 | }

vlib/v/checker/tests/union_unsafe_fields.vv

@@ -0,0 +1,12 @@
+union Uf32 {
+mut:
+	f f32
+	u u32
+}
+
+fn f() f32 {
+	mut u := Uf32{u: 3}
+	u.f = 3.3 // ok
+	_ := u.u
+	return &u.f
+}

vlib/v/parser/parser.v

@@ -1528,13 +1528,12 @@ fn (mut p Parser) dot_expr(left ast.Expr) ast.Expr {
 		is_mut: is_mut
 		mut_pos: mut_pos
 		scope: p.scope
+		next_token: p.tok.kind
 	}
-	mut node := ast.Expr{}
-	node = sel_expr
 	if is_filter {
 		p.close_scope()
 	}
-	return node
+	return sel_expr
 }
 
 // `.green`