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cmd/compile/internal/syntax: better error message when type parameters are not permitted

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Fixes #48382.

Change-Id: I215896a4429839c41c9136b6922b1b748ed47734
Reviewed-on: https://go-review.googlesource.com/c/go/+/361259
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>
This commit is contained in:
Robert Griesemer 2021-11-03 14:58:59 -07:00
parent 9cf6711067
commit a419f2f5c3
2 changed files with 43 additions and 17 deletions
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45
src/cmd/compile/internal/syntax/parser.go
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@ -708,15 +708,7 @@ func (p *parser) funcDeclOrNil() *FuncDecl {
}
f.Name = p.name()
if p.allowGenerics() && p.got(_Lbrack) {
if p.tok == _Rbrack {
p.syntaxError("empty type parameter list")
p.next()
} else {
f.TParamList = p.paramList(nil, _Rbrack, true)
}
}
f.Type = p.funcType()
f.TParamList, f.Type = p.funcType("")
if p.tok == _Lbrace {
f.Body = p.funcBody()
}
@ -944,7 +936,7 @@ func (p *parser) operand(keep_parens bool) Expr {
case _Func:
pos := p.pos()
p.next()
ftyp := p.funcType()
_, ftyp := p.funcType("function literal")
if p.tok == _Lbrace {
p.xnest++
@ -1284,7 +1276,8 @@ func (p *parser) typeOrNil() Expr {
case _Func:
// fntype
p.next()
return p.funcType()
_, t := p.funcType("function type")
return t
case _Lbrack:
// '[' oexpr ']' ntype
@ -1357,18 +1350,34 @@ func (p *parser) typeInstance(typ Expr) Expr {
return x
}
func (p *parser) funcType() *FuncType {
// If context != "", type parameters are not permitted.
func (p *parser) funcType(context string) ([]*Field, *FuncType) {
if trace {
defer p.trace("funcType")()
}
typ := new(FuncType)
typ.pos = p.pos()
var tparamList []*Field
if p.allowGenerics() && p.got(_Lbrack) {
if context != "" {
// accept but complain
p.syntaxErrorAt(typ.pos, context+" cannot have type parameters")
}
if p.tok == _Rbrack {
p.syntaxError("empty type parameter list")
p.next()
} else {
tparamList = p.paramList(nil, _Rbrack, true)
}
}
p.want(_Lparen)
typ.ParamList = p.paramList(nil, _Rparen, false)
typ.ResultList = p.funcResult()
return typ
return tparamList, typ
}
// "[" has already been consumed, and pos is its position.
@ -1697,11 +1706,13 @@ func (p *parser) methodDecl() *Field {
// already progressed, no need to advance
}
const context = "interface method"
switch p.tok {
case _Lparen:
// method
f.Name = name
f.Type = p.funcType()
_, f.Type = p.funcType(context)
case _Lbrack:
if p.allowGenerics() {
@ -1721,7 +1732,7 @@ func (p *parser) methodDecl() *Field {
// name[](
p.errorAt(pos, "empty type parameter list")
f.Name = name
f.Type = p.funcType()
_, f.Type = p.funcType(context)
} else {
p.errorAt(pos, "empty type argument list")
f.Type = name
@ -1738,7 +1749,7 @@ func (p *parser) methodDecl() *Field {
// as if [] were absent.
if p.tok == _Lparen {
f.Name = name
f.Type = p.funcType()
_, f.Type = p.funcType(context)
} else {
f.Type = name
}
@ -1749,7 +1760,7 @@ func (p *parser) methodDecl() *Field {
if list[0].Name != nil {
// generic method
f.Name = name
f.Type = p.funcType()
_, f.Type = p.funcType(context)
// TODO(gri) Record list as type parameter list with f.Type
// if we want to type-check the generic method.
// For now, report an error so this is not a silent event.