range.go

     1  // Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
     2  // Source: ../../cmd/compile/internal/types2/range.go
     3  
     4  // Copyright 2025 The Go Authors. All rights reserved.
     5  // Use of this source code is governed by a BSD-style
     6  // license that can be found in the LICENSE file.
     7  
     8  // This file implements typechecking of range statements.
     9  
    10  package types
    11  
    12  import (
    13  	"go/ast"
    14  	"go/constant"
    15  	"internal/buildcfg"
    16  	. "internal/types/errors"
    17  )
    18  
    19  // rangeStmt type-checks a range statement of form
    20  //
    21  //	for sKey, sValue = range rangeVar { ... }
    22  //
    23  // where sKey, sValue, sExtra may be nil. isDef indicates whether these
    24  // variables are assigned to only (=) or whether there is a short variable
    25  // declaration (:=). If the latter and there are no variables, an error is
    26  // reported at noNewVarPos.
    27  func (check *Checker) rangeStmt(inner stmtContext, rangeStmt *ast.RangeStmt, noNewVarPos positioner, sKey, sValue, sExtra, rangeVar ast.Expr, isDef bool) {
    28  	// check expression to iterate over
    29  	var x operand
    30  
    31  	// From the spec:
    32  	//   The range expression x is evaluated before beginning the loop,
    33  	//   with one exception: if at most one iteration variable is present
    34  	//   and x or len(x) is constant, the range expression is not evaluated.
    35  	// So we have to be careful not to evaluate the arg in the
    36  	// described situation.
    37  
    38  	check.hasCallOrRecv = false
    39  	check.expr(nil, &x, rangeVar)
    40  
    41  	if isTypes2 && x.mode != invalid && sValue == nil && !check.hasCallOrRecv {
    42  		if t, ok := arrayPtrDeref(under(x.typ)).(*Array); ok {
    43  			for {
    44  				// Put constant info on the thing inside parentheses.
    45  				// That's where (*../noder/writer).expr expects it.
    46  				// See issue 73476.
    47  				p, ok := rangeVar.(*ast.ParenExpr)
    48  				if !ok {
    49  					break
    50  				}
    51  				rangeVar = p.X
    52  			}
    53  			// Override type of rangeVar to be a constant
    54  			// (and thus side-effects will not be computed
    55  			// by the backend).
    56  			check.record(&operand{
    57  				mode: constant_,
    58  				expr: rangeVar,
    59  				typ:  Typ[Int],
    60  				val:  constant.MakeInt64(t.len),
    61  				id:   x.id,
    62  			})
    63  		}
    64  	}
    65  
    66  	// determine key/value types
    67  	var key, val Type
    68  	if x.mode != invalid {
    69  		k, v, cause, ok := rangeKeyVal(check, x.typ, func(v goVersion) bool {
    70  			return check.allowVersion(v)
    71  		})
    72  		switch {
    73  		case !ok && cause != "":
    74  			check.softErrorf(&x, InvalidRangeExpr, "cannot range over %s: %s", &x, cause)
    75  		case !ok:
    76  			check.softErrorf(&x, InvalidRangeExpr, "cannot range over %s", &x)
    77  		case k == nil && sKey != nil:
    78  			check.softErrorf(sKey, InvalidIterVar, "range over %s permits no iteration variables", &x)
    79  		case v == nil && sValue != nil:
    80  			check.softErrorf(sValue, InvalidIterVar, "range over %s permits only one iteration variable", &x)
    81  		case sExtra != nil:
    82  			check.softErrorf(sExtra, InvalidIterVar, "range clause permits at most two iteration variables")
    83  		}
    84  		key, val = k, v
    85  	}
    86  
    87  	// Open the for-statement block scope now, after the range clause.
    88  	// Iteration variables declared with := need to go in this scope (was go.dev/issue/51437).
    89  	check.openScope(rangeStmt, "range")
    90  	defer check.closeScope()
    91  
    92  	// check assignment to/declaration of iteration variables
    93  	// (irregular assignment, cannot easily map to existing assignment checks)
    94  
    95  	// lhs expressions and initialization value (rhs) types
    96  	lhs := [2]ast.Expr{sKey, sValue} // sKey, sValue may be nil
    97  	rhs := [2]Type{key, val}         // key, val may be nil
    98  
    99  	rangeOverInt := isInteger(x.typ)
   100  
   101  	if isDef {
   102  		// short variable declaration
   103  		var vars []*Var
   104  		for i, lhs := range lhs {
   105  			if lhs == nil {
   106  				continue
   107  			}
   108  
   109  			// determine lhs variable
   110  			var obj *Var
   111  			if ident, _ := lhs.(*ast.Ident); ident != nil {
   112  				// declare new variable
   113  				name := ident.Name
   114  				obj = newVar(LocalVar, ident.Pos(), check.pkg, name, nil)
   115  				check.recordDef(ident, obj)
   116  				// _ variables don't count as new variables
   117  				if name != "_" {
   118  					vars = append(vars, obj)
   119  				}
   120  			} else {
   121  				check.errorf(lhs, InvalidSyntaxTree, "cannot declare %s", lhs)
   122  				obj = newVar(LocalVar, lhs.Pos(), check.pkg, "_", nil) // dummy variable
   123  			}
   124  			assert(obj.typ == nil)
   125  
   126  			// initialize lhs iteration variable, if any
   127  			typ := rhs[i]
   128  			if typ == nil || typ == Typ[Invalid] {
   129  				// typ == Typ[Invalid] can happen if allowVersion fails.
   130  				obj.typ = Typ[Invalid]
   131  				check.usedVars[obj] = true // don't complain about unused variable
   132  				continue
   133  			}
   134  
   135  			if rangeOverInt {
   136  				assert(i == 0) // at most one iteration variable (rhs[1] == nil or Typ[Invalid] for rangeOverInt)
   137  				check.initVar(obj, &x, "range clause")
   138  			} else {
   139  				var y operand
   140  				y.mode = value
   141  				y.expr = lhs // we don't have a better rhs expression to use here
   142  				y.typ = typ
   143  				check.initVar(obj, &y, "assignment") // error is on variable, use "assignment" not "range clause"
   144  			}
   145  			assert(obj.typ != nil)
   146  		}
   147  
   148  		// declare variables
   149  		if len(vars) > 0 {
   150  			scopePos := rangeStmt.Body.Pos()
   151  			for _, obj := range vars {
   152  				check.declare(check.scope, nil /* recordDef already called */, obj, scopePos)
   153  			}
   154  		} else {
   155  			check.error(noNewVarPos, NoNewVar, "no new variables on left side of :=")
   156  		}
   157  	} else if sKey != nil /* lhs[0] != nil */ {
   158  		// ordinary assignment
   159  		for i, lhs := range lhs {
   160  			if lhs == nil {
   161  				continue
   162  			}
   163  
   164  			// assign to lhs iteration variable, if any
   165  			typ := rhs[i]
   166  			if typ == nil || typ == Typ[Invalid] {
   167  				continue
   168  			}
   169  
   170  			if rangeOverInt {
   171  				assert(i == 0) // at most one iteration variable (rhs[1] == nil or Typ[Invalid] for rangeOverInt)
   172  				check.assignVar(lhs, nil, &x, "range clause")
   173  				// If the assignment succeeded, if x was untyped before, it now
   174  				// has a type inferred via the assignment. It must be an integer.
   175  				// (go.dev/issues/67027)
   176  				if x.mode != invalid && !isInteger(x.typ) {
   177  					check.softErrorf(lhs, InvalidRangeExpr, "cannot use iteration variable of type %s", x.typ)
   178  				}
   179  			} else {
   180  				var y operand
   181  				y.mode = value
   182  				y.expr = lhs // we don't have a better rhs expression to use here
   183  				y.typ = typ
   184  				check.assignVar(lhs, nil, &y, "assignment") // error is on variable, use "assignment" not "range clause"
   185  			}
   186  		}
   187  	} else if rangeOverInt {
   188  		// If we don't have any iteration variables, we still need to
   189  		// check that a (possibly untyped) integer range expression x
   190  		// is valid.
   191  		// We do this by checking the assignment _ = x. This ensures
   192  		// that an untyped x can be converted to a value of its default
   193  		// type (rune or int).
   194  		check.assignment(&x, nil, "range clause")
   195  	}
   196  
   197  	check.stmt(inner, rangeStmt.Body)
   198  }
   199  
   200  // rangeKeyVal returns the key and value type produced by a range clause
   201  // over an expression of type orig.
   202  // If allowVersion != nil, it is used to check the required language version.
   203  // If the range clause is not permitted, rangeKeyVal returns ok = false.
   204  // When ok = false, rangeKeyVal may also return a reason in cause.
   205  // The check parameter is only used in case of an error; it may be nil.
   206  func rangeKeyVal(check *Checker, orig Type, allowVersion func(goVersion) bool) (key, val Type, cause string, ok bool) {
   207  	bad := func(cause string) (Type, Type, string, bool) {
   208  		return Typ[Invalid], Typ[Invalid], cause, false
   209  	}
   210  
   211  	rtyp, err := commonUnder(orig, func(t, u Type) *typeError {
   212  		// A channel must permit receive operations.
   213  		if ch, _ := u.(*Chan); ch != nil && ch.dir == SendOnly {
   214  			return typeErrorf("receive from send-only channel %s", t)
   215  		}
   216  		return nil
   217  	})
   218  	if rtyp == nil {
   219  		return bad(err.format(check))
   220  	}
   221  
   222  	switch typ := arrayPtrDeref(rtyp).(type) {
   223  	case *Basic:
   224  		if isString(typ) {
   225  			return Typ[Int], universeRune, "", true // use 'rune' name
   226  		}
   227  		if isInteger(typ) {
   228  			if allowVersion != nil && !allowVersion(go1_22) {
   229  				return bad("requires go1.22 or later")
   230  			}
   231  			return orig, nil, "", true
   232  		}
   233  	case *Array:
   234  		return Typ[Int], typ.elem, "", true
   235  	case *Slice:
   236  		return Typ[Int], typ.elem, "", true
   237  	case *Map:
   238  		return typ.key, typ.elem, "", true
   239  	case *Chan:
   240  		assert(typ.dir != SendOnly)
   241  		return typ.elem, nil, "", true
   242  	case *Signature:
   243  		if !buildcfg.Experiment.RangeFunc && allowVersion != nil && !allowVersion(go1_23) {
   244  			return bad("requires go1.23 or later")
   245  		}
   246  		// check iterator arity
   247  		switch {
   248  		case typ.Params().Len() != 1:
   249  			return bad("func must be func(yield func(...) bool): wrong argument count")
   250  		case typ.Results().Len() != 0:
   251  			return bad("func must be func(yield func(...) bool): unexpected results")
   252  		}
   253  		assert(typ.Recv() == nil)
   254  		// check iterator argument type
   255  		u, err := commonUnder(typ.Params().At(0).Type(), nil)
   256  		cb, _ := u.(*Signature)
   257  		switch {
   258  		case cb == nil:
   259  			if err != nil {
   260  				return bad(check.sprintf("func must be func(yield func(...) bool): in yield type, %s", err.format(check)))
   261  			} else {
   262  				return bad("func must be func(yield func(...) bool): argument is not func")
   263  			}
   264  		case cb.Params().Len() > 2:
   265  			return bad("func must be func(yield func(...) bool): yield func has too many parameters")
   266  		case cb.Results().Len() != 1 || !Identical(cb.Results().At(0).Type(), universeBool):
   267  			// see go.dev/issues/71131, go.dev/issues/71164
   268  			if cb.Results().Len() == 1 && isBoolean(cb.Results().At(0).Type()) {
   269  				return bad("func must be func(yield func(...) bool): yield func returns user-defined boolean, not bool")
   270  			} else {
   271  				return bad("func must be func(yield func(...) bool): yield func does not return bool")
   272  			}
   273  		}
   274  		assert(cb.Recv() == nil)
   275  		// determine key and value types, if any
   276  		if cb.Params().Len() >= 1 {
   277  			key = cb.Params().At(0).Type()
   278  		}
   279  		if cb.Params().Len() >= 2 {
   280  			val = cb.Params().At(1).Type()
   281  		}
   282  		return key, val, "", true
   283  	}
   284  	return
   285  }
   286
View as plain text