parser: move mut in if/match to expr (#6973)

vlib/v/ast/ast.v

@@ -106,6 +106,8 @@ pub:
 	pos        token.Position
 	expr       Expr // expr.field_name
 	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
 pub mut:
 	expr_type  table.Type // type of `Foo` in `Foo.bar`
 	typ        table.Type // type of the entire thing (`Foo.bar`)
@@ -447,6 +449,7 @@ pub:
 	language table.Language
 	tok_kind token.Kind
 	pos      token.Position
+	mut_pos  token.Position
 pub mut:
 	obj      ScopeObject
 	mod      string
@@ -533,7 +536,6 @@ pub:
 	pos       token.Position
 	body_pos  token.Position
 	comments  []Comment
-	is_mut_name bool // `if mut name is`
 pub mut:
 	stmts     []Stmt
 	smartcast bool // true when cond is `x is SumType`, set in checker.if_expr // no longer needed with union sum types TODO: remove
@@ -562,7 +564,6 @@ pub:
 	cond          Expr
 	branches      []MatchBranch
 	pos           token.Position
-	is_mut        bool // `match mut ast_node {`
 pub mut:
 	is_expr       bool // returns a value
 	return_type   table.Type

vlib/v/ast/scope.v

@@ -202,21 +202,3 @@ pub fn (sc &Scope) show(depth int, max_depth int) string {
 pub fn (sc &Scope) str() string {
 	return sc.show(0, 0)
 }
-
-// is_selector_root_mutable checks if the root ident is mutable
-// Example:
-// ```
-// mut x := MyStruct{}
-// x.foo.bar.z
-// ```
-// Since x is mutable, it returns true.
-pub fn (s &Scope) is_selector_root_mutable(t &table.Table, selector_expr SelectorExpr) bool {
-	if mut selector_expr.expr is SelectorExpr {
-		return s.is_selector_root_mutable(t, selector_expr.expr)
-	} else if mut selector_expr.expr is Ident {
-		if v := s.find_var(selector_expr.expr.name) {
-			return v.is_mut
-		}
-	}
-	return false
-}

vlib/v/checker/checker.v

@@ -623,6 +623,16 @@ pub fn (mut c Checker) infix_expr(mut infix_expr ast.InfixExpr) table.Type {
 		c.warn('pointer arithmetic is only allowed in `unsafe` blocks', left_pos)
 	}
 	mut return_type := left_type
+	if infix_expr.op != .key_is {
+		match mut infix_expr.left {
+			ast.Ident, ast.SelectorExpr {
+				if infix_expr.left.is_mut {
+					c.error('remove unnecessary `mut`', infix_expr.left.mut_pos)
+				}
+			}
+			else {}
+		}
+	}
 	// Single side check
 	// Place these branches according to ops' usage frequency to accelerate.
 	// TODO: First branch includes ops where single side check is not needed, or needed but hasn't been implemented.
@@ -3451,11 +3461,6 @@ pub fn (mut c Checker) match_expr(mut node ast.MatchExpr) table.Type {
 	// node.expected_type = c.expected_type
 	// }
 	node.return_type = ret_type
-	if node.is_mut {
-		// Mark `x` in `match mut x {` as changed, and ensure it's mutable
-		// TODO2 enable when code is fixed
-		// c.fail_if_immutable(node.cond)
-	}
 	return ret_type
 }
 
@@ -3585,9 +3590,8 @@ fn (mut c Checker) match_exprs(mut node ast.MatchExpr, type_sym table.TypeSymbol
 						if field := scope.find_struct_field(node.cond.expr_type, node.cond.field_name) {
 							sum_type_casts << field.sum_type_casts
 						}
-						is_root_mut := scope.is_selector_root_mutable(c.table, node.cond)
 						// smartcast either if the value is immutable or if the mut argument is explicitly given
-						if (!is_root_mut && !is_mut) || node.is_mut {
+						if !is_mut || node.cond.is_mut {
 							sum_type_casts << expr_type
 							scope.register_struct_field(ast.ScopeStructField{
 								struct_type: node.cond.expr_type
@@ -3608,14 +3612,14 @@ fn (mut c Checker) match_exprs(mut node ast.MatchExpr, type_sym table.TypeSymbol
 							is_already_casted = v.pos.pos == node.cond.pos.pos
 						}
 						// smartcast either if the value is immutable or if the mut argument is explicitly given
-						if (!is_mut || node.is_mut) && !is_already_casted {
+						if (!is_mut || node.cond.is_mut) && !is_already_casted {
 							sum_type_casts << expr_type
 							scope.register(node.cond.name, ast.Var{
 								name: node.cond.name
 								typ: node.cond_type
 								pos: node.cond.pos
 								is_used: true
-								is_mut: node.is_mut
+								is_mut: node.cond.is_mut
 								sum_type_casts: sum_type_casts
 							})
 						}
@@ -3846,7 +3850,7 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) table.Type {
 								}
 								if left_sym.kind == .sum_type {
 									// smartcast either if the value is immutable or if the mut argument is explicitly given
-									if !is_mut || branch.is_mut_name {
+									if !is_mut || infix.left.is_mut {
 										sum_type_casts << right_expr.typ
 										scope.register(infix.left.name, ast.Var{
 											name: infix.left.name
@@ -3879,12 +3883,8 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) table.Type {
 									infix.left.field_name) {
 									sum_type_casts << field.sum_type_casts
 								}
-								is_root_mut := scope.is_selector_root_mutable(c.table,
-									infix.left)
 								// smartcast either if the value is immutable or if the mut argument is explicitly given
-								if ((!is_root_mut && !is_mut) ||
+								if (!is_mut || infix.left.is_mut) && left_sym.kind == .sum_type {
-									branch.is_mut_name) &&
-									left_sym.kind == .sum_type {
 									sum_type_casts << right_expr.typ
 									scope.register_struct_field(ast.ScopeStructField{
 										struct_type: infix.left.expr_type

vlib/v/fmt/fmt.v

@@ -251,9 +251,6 @@ pub fn (mut f Fmt) stmt(node ast.Stmt) {
 			for i, left in node.left {
 				if left is ast.Ident {
 					var_info := left.var_info()
-					if var_info.is_mut {
-						f.write(var_info.share.str() + ' ')
-					}
 					if var_info.is_static {
 						f.write('static ')
 					}
@@ -835,10 +832,12 @@ pub fn (mut f Fmt) expr(node ast.Expr) {
 			f.if_expr(node)
 		}
 		ast.Ident {
-			f.write_language_prefix(node.language)
+			if mut node.info is ast.IdentVar {
-			if true {
+				if node.info.is_mut {
-			} else {
+					f.write(node.info.share.str() + ' ')
 				}
+			}
+			f.write_language_prefix(node.language)
 			if node.name == 'it' && f.it_name != '' && !f.inside_lambda { // allow `it` in lambdas
 				f.write(f.it_name)
 			} else if node.kind == .blank_ident {
@@ -1411,9 +1410,6 @@ pub fn (mut f Fmt) if_expr(it ast.IfExpr) {
 		}
 		if i < it.branches.len - 1 || !it.has_else {
 			f.write('${dollar}if ')
-			if branch.is_mut_name {
-				f.write('mut ')
-			}
 			f.expr(branch.cond)
 			f.write(' ')
 		}
@@ -1532,9 +1528,6 @@ pub fn (mut f Fmt) call_expr(node ast.CallExpr) {
 
 pub fn (mut f Fmt) match_expr(it ast.MatchExpr) {
 	f.write('match ')
-	if it.is_mut {
-		f.write('mut ')
-	}
 	f.expr(it.cond)
 	if it.cond is ast.Ident {
 		f.it_name = it.cond.name

vlib/v/parser/if_match.v

@@ -84,15 +84,6 @@ fn (mut p Parser) if_expr(is_comptime bool) ast.IfExpr {
 			p.error('cannot use `match` with `if` statements')
 		}
 		comments << p.eat_comments()
-		// `if mut name is T`
-		mut is_mut_name := false
-		mut mut_pos := token.Position{}
-		if p.tok.kind == .key_mut {
-			is_mut_name = true
-			mut_pos = p.tok.position()
-			p.next()
-			comments << p.eat_comments()
-		}
 		mut cond := ast.Expr{}
 		mut is_guard := false
 		// `if x := opt() {`
@@ -120,15 +111,6 @@ fn (mut p Parser) if_expr(is_comptime bool) ast.IfExpr {
 			cond = p.expr(0)
 		}
 		comments << p.eat_comments()
-		if mut cond is ast.InfixExpr {
-			// if sum is T
-			is_is_cast := cond.op == .key_is
-			if !is_is_cast && is_mut_name {
-				p.error_with_pos('remove unnecessary `mut`', mut_pos)
-			}
-		} else if is_mut_name {
-			p.error_with_pos('remove unnecessary `mut`', mut_pos)
-		}
 		end_pos := p.prev_tok.position()
 		body_pos := p.tok.position()
 		p.inside_if = false
@@ -142,7 +124,6 @@ fn (mut p Parser) if_expr(is_comptime bool) ast.IfExpr {
 			pos: start_pos.extend(end_pos)
 			body_pos: body_pos.extend(p.prev_tok.position())
 			comments: comments
-			is_mut_name: is_mut_name
 		}
 		comments = p.eat_comments()
 		if is_comptime {
@@ -170,11 +151,7 @@ fn (mut p Parser) match_expr() ast.MatchExpr {
 	match_first_pos := p.tok.position()
 	p.inside_match = true
 	p.check(.key_match)
-	is_mut := p.tok.kind == .key_mut
 	mut is_sum_type := false
-	if is_mut {
-		p.next()
-	}
 	cond := p.expr(0)
 	p.inside_match = false
 	no_lcbr := p.tok.kind != .lcbr
@@ -281,7 +258,6 @@ fn (mut p Parser) match_expr() ast.MatchExpr {
 		cond: cond
 		is_sum_type: is_sum_type
 		pos: pos
-		is_mut: is_mut
 	}
 }
 

vlib/v/parser/parser.v

@@ -914,6 +914,7 @@ pub fn (mut p Parser) parse_ident(language table.Language) ast.Ident {
 	// p.warn('name ')
 	is_shared := p.tok.kind == .key_shared
 	is_atomic := p.tok.kind == .key_atomic
+	mut_pos := p.tok.position()
 	is_mut := p.tok.kind == .key_mut || is_shared || is_atomic
 	if is_mut {
 		p.next()
@@ -951,6 +952,7 @@ pub fn (mut p Parser) parse_ident(language table.Language) ast.Ident {
 			mod: p.mod
 			pos: pos
 			is_mut: is_mut
+			mut_pos: mut_pos
 			info: ast.IdentVar{
 				is_mut: is_mut
 				is_static: is_static
@@ -1349,10 +1351,22 @@ fn (mut p Parser) dot_expr(left ast.Expr) ast.Expr {
 		}
 		return mcall_expr
 	}
+	mut is_mut := false
+	mut mut_pos := token.Position{}
+	if p.inside_match || p.inside_if_expr {
+		match left {
+			ast.Ident, ast.SelectorExpr {
+				is_mut = left.is_mut
+				mut_pos = left.mut_pos
+			}
+			else {}
+		}
+	}
 	sel_expr := ast.SelectorExpr{
 		expr: left
 		field_name: field_name
 		pos: name_pos
+		is_mut: is_mut
 	}
 	mut node := ast.Expr{}
 	node = sel_expr

vlib/v/parser/tests/unnecessary_mut_2.out

@@ -1,6 +1,6 @@
-vlib/v/parser/tests/unnecessary_mut_2.vv:2:5: error: remove unnecessary `mut`
+vlib/v/parser/tests/unnecessary_mut_2.vv:2:9: error: unexpected token `true`
     1 | fn main() {
     2 |     if mut true {
-      |        ~~~
+      |            ~~~~
     3 |         println(true)
     4 |     }