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path: root/src/cmd/compile/internal/syntax/parser.go
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Diffstat (limited to 'src/cmd/compile/internal/syntax/parser.go')
-rw-r--r--src/cmd/compile/internal/syntax/parser.go149
1 files changed, 116 insertions, 33 deletions
diff --git a/src/cmd/compile/internal/syntax/parser.go b/src/cmd/compile/internal/syntax/parser.go
index 770175fe54..40c5eca408 100644
--- a/src/cmd/compile/internal/syntax/parser.go
+++ b/src/cmd/compile/internal/syntax/parser.go
@@ -588,44 +588,81 @@ func (p *parser) typeDecl(group *Group) Decl {
d.Name = p.name()
if p.allowGenerics() && p.tok == _Lbrack {
// d.Name "[" ...
- // array/slice or type parameter list
+ // array/slice type or type parameter list
pos := p.pos()
p.next()
switch p.tok {
case _Name:
- // d.Name "[" name ...
- // array or type parameter list
- name := p.name()
- // Index or slice expressions are never constant and thus invalid
- // array length expressions. Thus, if we see a "[" following name
- // we can safely assume that "[" name starts a type parameter list.
- var x Expr // x != nil means x is the array length expression
+ // We may have an array type or a type parameter list.
+ // In either case we expect an expression x (which may
+ // just be a name, or a more complex expression) which
+ // we can analyze further.
+ //
+ // A type parameter list may have a type bound starting
+ // with a "[" as in: P []E. In that case, simply parsing
+ // an expression would lead to an error: P[] is invalid.
+ // But since index or slice expressions are never constant
+ // and thus invalid array length expressions, if we see a
+ // "[" following a name it must be the start of an array
+ // or slice constraint. Only if we don't see a "[" do we
+ // need to parse a full expression.
+ var x Expr = p.name()
if p.tok != _Lbrack {
- // d.Name "[" name ...
- // If we reach here, the next token is not a "[", and we need to
- // parse the expression starting with name. If that expression is
- // just that name, not followed by a "]" (in which case we might
- // have the array length "[" name "]"), we can also safely assume
- // a type parameter list.
+ // To parse the expression starting with name, expand
+ // the call sequence we would get by passing in name
+ // to parser.expr, and pass in name to parser.pexpr.
p.xnest++
- // To parse the expression starting with name, expand the call
- // sequence we would get by passing in name to parser.expr, and
- // pass in name to parser.pexpr.
- x = p.binaryExpr(p.pexpr(name, false), 0)
+ x = p.binaryExpr(p.pexpr(x, false), 0)
p.xnest--
- if x == name && p.tok != _Rbrack {
- x = nil
+ }
+
+ // analyze the cases
+ var pname *Name // pname != nil means pname is the type parameter name
+ var ptype Expr // ptype != nil means ptype is the type parameter type; pname != nil in this case
+ switch t := x.(type) {
+ case *Name:
+ // Unless we see a "]", we are at the start of a type parameter list.
+ if p.tok != _Rbrack {
+ // d.Name "[" name ...
+ pname = t
+ // no ptype
+ }
+ case *Operation:
+ // If we have an expression of the form name*T, and T is a (possibly
+ // parenthesized) type literal or the next token is a comma, we are
+ // at the start of a type parameter list.
+ if name, _ := t.X.(*Name); name != nil {
+ if t.Op == Mul && (isTypeLit(t.Y) || p.tok == _Comma) {
+ // d.Name "[" name "*" t.Y
+ // d.Name "[" name "*" t.Y ","
+ t.X, t.Y = t.Y, nil // convert t into unary *t.Y
+ pname = name
+ ptype = t
+ }
+ }
+ case *CallExpr:
+ // If we have an expression of the form name(T), and T is a (possibly
+ // parenthesized) type literal or the next token is a comma, we are
+ // at the start of a type parameter list.
+ if name, _ := t.Fun.(*Name); name != nil {
+ if len(t.ArgList) == 1 && !t.HasDots && (isTypeLit(t.ArgList[0]) || p.tok == _Comma) {
+ // d.Name "[" name "(" t.ArgList[0] ")"
+ // d.Name "[" name "(" t.ArgList[0] ")" ","
+ pname = name
+ ptype = t.ArgList[0]
+ }
}
}
- if x == nil {
- // d.Name "[" name ...
- // type parameter list
- d.TParamList = p.paramList(name, _Rbrack, true)
+
+ if pname != nil {
+ // d.Name "[" pname ...
+ // d.Name "[" pname ptype ...
+ // d.Name "[" pname ptype "," ...
+ d.TParamList = p.paramList(pname, ptype, _Rbrack, true)
d.Alias = p.gotAssign()
d.Type = p.typeOrNil()
} else {
- // d.Name "[" x "]" ...
- // x is the array length expression
+ // d.Name "[" x ...
d.Type = p.arrayType(pos, x)
}
case _Rbrack:
@@ -650,6 +687,21 @@ func (p *parser) typeDecl(group *Group) Decl {
return d
}
+// isTypeLit reports whether x is a (possibly parenthesized) type literal.
+func isTypeLit(x Expr) bool {
+ switch x := x.(type) {
+ case *ArrayType, *StructType, *FuncType, *InterfaceType, *SliceType, *MapType, *ChanType:
+ return true
+ case *Operation:
+ // *T may be a pointer dereferenciation.
+ // Only consider *T as type literal if T is a type literal.
+ return x.Op == Mul && x.Y == nil && isTypeLit(x.X)
+ case *ParenExpr:
+ return isTypeLit(x.X)
+ }
+ return false
+}
+
// VarSpec = IdentifierList ( Type [ "=" ExpressionList ] | "=" ExpressionList ) .
func (p *parser) varDecl(group *Group) Decl {
if trace {
@@ -689,7 +741,7 @@ func (p *parser) funcDeclOrNil() *FuncDecl {
f.Pragma = p.takePragma()
if p.got(_Lparen) {
- rcvr := p.paramList(nil, _Rparen, false)
+ rcvr := p.paramList(nil, nil, _Rparen, false)
switch len(rcvr) {
case 0:
p.error("method has no receiver")
@@ -1369,12 +1421,12 @@ func (p *parser) funcType(context string) ([]*Field, *FuncType) {
p.syntaxError("empty type parameter list")
p.next()
} else {
- tparamList = p.paramList(nil, _Rbrack, true)
+ tparamList = p.paramList(nil, nil, _Rbrack, true)
}
}
p.want(_Lparen)
- typ.ParamList = p.paramList(nil, _Rparen, false)
+ typ.ParamList = p.paramList(nil, nil, _Rparen, false)
typ.ResultList = p.funcResult()
return tparamList, typ
@@ -1392,6 +1444,13 @@ func (p *parser) arrayType(pos Pos, len Expr) Expr {
len = p.expr()
p.xnest--
}
+ if p.tok == _Comma {
+ // Trailing commas are accepted in type parameter
+ // lists but not in array type declarations.
+ // Accept for better error handling but complain.
+ p.syntaxError("unexpected comma; expecting ]")
+ p.next()
+ }
p.want(_Rbrack)
t := new(ArrayType)
t.pos = pos
@@ -1516,7 +1575,7 @@ func (p *parser) funcResult() []*Field {
}
if p.got(_Lparen) {
- return p.paramList(nil, _Rparen, false)
+ return p.paramList(nil, nil, _Rparen, false)
}
pos := p.pos()
@@ -1742,7 +1801,7 @@ func (p *parser) methodDecl() *Field {
// A type argument list looks like a parameter list with only
// types. Parse a parameter list and decide afterwards.
- list := p.paramList(nil, _Rbrack, false)
+ list := p.paramList(nil, nil, _Rbrack, false)
if len(list) == 0 {
// The type parameter list is not [] but we got nothing
// due to other errors (reported by paramList). Treat
@@ -1948,17 +2007,41 @@ func (p *parser) paramDeclOrNil(name *Name, follow token) *Field {
// ParameterList = ParameterDecl { "," ParameterDecl } .
// "(" or "[" has already been consumed.
// If name != nil, it is the first name after "(" or "[".
+// If typ != nil, name must be != nil, and (name, typ) is the first field in the list.
// In the result list, either all fields have a name, or no field has a name.
-func (p *parser) paramList(name *Name, close token, requireNames bool) (list []*Field) {
+func (p *parser) paramList(name *Name, typ Expr, close token, requireNames bool) (list []*Field) {
if trace {
defer p.trace("paramList")()
}
+ // p.list won't invoke its function argument if we're at the end of the
+ // parameter list. If we have a complete field, handle this case here.
+ if name != nil && typ != nil && p.tok == close {
+ p.next()
+ par := new(Field)
+ par.pos = name.pos
+ par.Name = name
+ par.Type = typ
+ return []*Field{par}
+ }
+
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, close)
+ var par *Field
+ if typ != nil {
+ if debug && name == nil {
+ panic("initial type provided without name")
+ }
+ par = new(Field)
+ par.pos = name.pos
+ par.Name = name
+ par.Type = typ
+ } else {
+ par = p.paramDeclOrNil(name, close)
+ }
name = nil // 1st name was consumed if present
+ typ = nil // 1st type was consumed if present
if par != nil {
if debug && par.Name == nil && par.Type == nil {
panic("parameter without name or type")
generated by cgit v1.3-5-g9baa (git 2.53.0) at 2026-04-17 05:29:39 +0000