go/types: typecheck loop body even if range clause is broken
Be more tolerant in the presence of incorrect range clauses if for loops and type-check loop body with minimal assumptions about iteration variables. (Before, in some cases we would simply ignore the loop body in such cases). Fixes #10148. Change-Id: I0b66f81875348088c1a7fa04ccdcbfe768f2eb6c Reviewed-on: https://go-review.googlesource.com/7525 Reviewed-by: Alan Donovan <adonovan@google.com>
This commit is contained in:
Robert Griesemer
parent
868c429971
commit
e4a1c78f0f
100
go/types/stmt.go
100
go/types/stmt.go
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@ -611,60 +611,49 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
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defer check.closeScope()
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// check expression to iterate over
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decl := s.Tok == token.DEFINE
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var x operand
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check.expr(&x, s.X)
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if x.mode == invalid {
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// if we don't have a declaration, we can still check the loop's body
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// (otherwise we can't because we are missing the declared variables)
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if !decl {
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check.stmt(inner, s.Body)
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}
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return
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}
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// determine key/value types
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var key, val Type
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switch typ := x.typ.Underlying().(type) {
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case *Basic:
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if isString(typ) {
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key = Typ[Int]
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val = UniverseRune // use 'rune' name
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}
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case *Array:
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key = Typ[Int]
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val = typ.elem
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case *Slice:
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key = Typ[Int]
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val = typ.elem
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case *Pointer:
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if typ, _ := typ.base.Underlying().(*Array); typ != nil {
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if x.mode != invalid {
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switch typ := x.typ.Underlying().(type) {
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case *Basic:
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if isString(typ) {
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key = Typ[Int]
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val = UniverseRune // use 'rune' name
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}
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case *Array:
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key = Typ[Int]
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val = typ.elem
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}
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case *Map:
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key = typ.key
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val = typ.elem
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case *Chan:
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key = typ.elem
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val = Typ[Invalid]
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if typ.dir == SendOnly {
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check.errorf(x.pos(), "cannot range over send-only channel %s", &x)
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// ok to continue
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}
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if s.Value != nil {
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check.errorf(s.Value.Pos(), "iteration over %s permits only one iteration variable", &x)
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// ok to continue
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case *Slice:
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key = Typ[Int]
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val = typ.elem
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case *Pointer:
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if typ, _ := typ.base.Underlying().(*Array); typ != nil {
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key = Typ[Int]
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val = typ.elem
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}
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case *Map:
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key = typ.key
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val = typ.elem
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case *Chan:
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key = typ.elem
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val = Typ[Invalid]
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if typ.dir == SendOnly {
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check.errorf(x.pos(), "cannot range over send-only channel %s", &x)
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// ok to continue
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}
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if s.Value != nil {
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check.errorf(s.Value.Pos(), "iteration over %s permits only one iteration variable", &x)
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// ok to continue
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}
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}
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}
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if key == nil {
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check.errorf(x.pos(), "cannot range over %s", &x)
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// if we don't have a declaration, we can still check the loop's body
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if !decl {
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check.stmt(inner, s.Body)
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}
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return
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// ok to continue
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}
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// check assignment to/declaration of iteration variables
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@ -672,9 +661,9 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
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// lhs expressions and initialization value (rhs) types
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lhs := [2]ast.Expr{s.Key, s.Value}
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rhs := [2]Type{key, val}
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rhs := [2]Type{key, val} // key, val may be nil
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if decl {
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if s.Tok == token.DEFINE {
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// short variable declaration; variable scope starts after the range clause
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// (the for loop opens a new scope, so variables on the lhs never redeclare
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// previously declared variables)
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@ -701,10 +690,15 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
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}
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// initialize lhs variable
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x.mode = value
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x.expr = lhs // we don't have a better rhs expression to use here
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x.typ = rhs[i]
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check.initVar(obj, &x, false)
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if typ := rhs[i]; typ != nil {
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x.mode = value
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x.expr = lhs // we don't have a better rhs expression to use here
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x.typ = typ
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check.initVar(obj, &x, false)
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} else {
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obj.typ = Typ[Invalid]
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obj.used = true // don't complain about unused variable
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}
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}
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// declare variables
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@ -721,10 +715,12 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) {
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if lhs == nil {
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continue
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}
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x.mode = value
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x.expr = lhs // we don't have a better rhs expression to use here
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x.typ = rhs[i]
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check.assignVar(lhs, &x)
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if typ := rhs[i]; typ != nil {
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x.mode = value
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x.expr = lhs // we don't have a better rhs expression to use here
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x.typ = typ
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check.assignVar(lhs, &x)
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}
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}
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}
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@ -785,6 +785,21 @@ func issue6766b() {
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for a, a /* ERROR redeclared */ := range []int{1, 2, 3} { _ = a }
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}
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// Test that despite errors in the range clause,
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// the loop body is still type-checked (and thus
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// errors reported).
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func issue10148() {
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for y /* ERROR declared but not used */ := range "" {
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_ = "" /* ERROR cannot convert */ + 1
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}
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for range 1 /* ERROR cannot range over 1 */ {
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_ = "" /* ERROR cannot convert */ + 1
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}
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for y := range 1 /* ERROR cannot range over 1 */ {
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_ = "" /* ERROR cannot convert */ + 1
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}
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}
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func labels0() {
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goto L0
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goto L1
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