From 73483df406af39e6c244fd2fb90b41c4cfecd51e Mon Sep 17 00:00:00 2001 From: Robert Griesemer Date: Wed, 8 Sep 2021 21:30:01 -0700 Subject: cmd/compile/internal/syntax: better error message for missing type constraint For #43527. Change-Id: I8c706e68572286d5675383eb2dfd75b5618b646b Reviewed-on: https://go-review.googlesource.com/c/go/+/348730 Trust: Robert Griesemer Run-TryBot: Robert Griesemer TryBot-Result: Go Bot Reviewed-by: Robert Findley --- src/cmd/compile/internal/syntax/parser.go | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) (limited to 'src/cmd/compile/internal/syntax/parser.go') diff --git a/src/cmd/compile/internal/syntax/parser.go b/src/cmd/compile/internal/syntax/parser.go index e89796cb31..c836a21c2f 100644 --- a/src/cmd/compile/internal/syntax/parser.go +++ b/src/cmd/compile/internal/syntax/parser.go @@ -1908,8 +1908,9 @@ func (p *parser) paramList(name *Name, close token, requireNames bool) (list []* defer p.trace("paramList")() } - var named int // number of parameters that have an explicit name and type/bound - p.list(_Comma, close, func() bool { + var named int // number of parameters that have an explicit name and type + var typed int // number of parameters that have an explicit type + end := p.list(_Comma, close, func() bool { par := p.paramDeclOrNil(name) name = nil // 1st name was consumed if present if par != nil { @@ -1919,6 +1920,9 @@ func (p *parser) paramList(name *Name, close token, requireNames bool) (list []* if par.Name != nil && par.Type != nil { named++ } + if par.Type != nil { + typed++ + } list = append(list, par) } return false @@ -1939,10 +1943,11 @@ func (p *parser) paramList(name *Name, close token, requireNames bool) (list []* } } else if named != len(list) { // some named => all must have names and types - var pos Pos // left-most error position (or unknown) - var typ Expr + var pos Pos // left-most error position (or unknown) + var typ Expr // current type (from right to left) for i := len(list) - 1; i >= 0; i-- { - if par := list[i]; par.Type != nil { + par := list[i] + if par.Type != nil { typ = par.Type if par.Name == nil { pos = typ.Pos() @@ -1961,7 +1966,12 @@ func (p *parser) paramList(name *Name, close token, requireNames bool) (list []* if pos.IsKnown() { var msg string if requireNames { - msg = "type parameters must be named" + if named == typed { + pos = end // position error at closing ] + msg = "missing type constraint" + } else { + msg = "type parameters must be named" + } } else { msg = "mixed named and unnamed parameters" } -- cgit v1.3-5-g9baa