Revert "cmd/compile/internal/syntax: support for alias declarations"

This reverts commit 32db3f2756324616b7c856ac9501deccc2491239.

Reason: Decision to back out current alias implementation.

For #16339.

Change-Id: Ib05e3d96041d8347e49cae292f66bec791a1fdc8
Reviewed-on: https://go-review.googlesource.com/32825
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 30 insertions, 68 deletions

diff --git a/src/cmd/compile/internal/syntax/parser.go b/src/cmd/compile/internal/syntax/parser.go
index 1ed20651b1..a959c6cd25 100644
--- a/src/cmd/compile/internal/syntax/parser.go
+++ b/src/cmd/compile/internal/syntax/parser.go
@@ -317,38 +317,16 @@ func (p *parser) importDecl(group *Group) Decl {
 	return d
 }
 
-// AliasSpec = identifier "=>" [ PackageName "." ] identifier .
-func (p *parser) aliasDecl(tok token, name *Name, group *Group) Decl {
-	// no tracing since this is already called from a const/type/var/funcDecl
-
-	d := new(AliasDecl)
-	d.initFrom(&name.node)
-
-	// lhs identifier and "=>" have been consumed already
-
-	d.Tok = tok
-	d.Name = name
-	d.Orig = p.dotname(p.name())
-	d.Group = group
-
-	return d
-}
-
-// ConstSpec = IdentifierList [ [ Type ] "=" ExpressionList ] | AliasSpec .
+// ConstSpec = IdentifierList [ [ Type ] "=" ExpressionList ] .
 func (p *parser) constDecl(group *Group) Decl {
 	if trace {
 		defer p.trace("constDecl")()
 	}
 
-	name := p.name()
-	if p.got(_Rarrow) {
-		return p.aliasDecl(Const, name, group)
-	}
-
 	d := new(ConstDecl)
-	d.initFrom(&name.node)
+	d.init(p)
 
-	d.NameList = p.nameList(name)
+	d.NameList = p.nameList(p.name())
 	if p.tok != _EOF && p.tok != _Semi && p.tok != _Rparen {
 		d.Type = p.tryType()
 		if p.got(_Assign) {
@@ -360,21 +338,16 @@ func (p *parser) constDecl(group *Group) Decl {
 	return d
 }
 
-// TypeSpec = identifier Type | AliasSpec .
+// TypeSpec = identifier Type .
 func (p *parser) typeDecl(group *Group) Decl {
 	if trace {
 		defer p.trace("typeDecl")()
 	}
 
-	name := p.name()
-	if p.got(_Rarrow) {
-		return p.aliasDecl(Type, name, group)
-	}
-
 	d := new(TypeDecl)
-	d.initFrom(&name.node)
+	d.init(p)
 
-	d.Name = name
+	d.Name = p.name()
 	d.Type = p.tryType()
 	if d.Type == nil {
 		p.syntax_error("in type declaration")
@@ -386,21 +359,16 @@ func (p *parser) typeDecl(group *Group) Decl {
 	return d
 }
 
-// VarSpec = IdentifierList ( Type [ "=" ExpressionList ] | "=" ExpressionList ) | AliasSpec .
+// VarSpec = IdentifierList ( Type [ "=" ExpressionList ] | "=" ExpressionList ) .
 func (p *parser) varDecl(group *Group) Decl {
 	if trace {
 		defer p.trace("varDecl")()
 	}
 
-	name := p.name()
-	if p.got(_Rarrow) {
-		return p.aliasDecl(Var, name, group)
-	}
-
 	d := new(VarDecl)
-	d.initFrom(&name.node)
+	d.init(p)
 
-	d.NameList = p.nameList(name)
+	d.NameList = p.nameList(p.name())
 	if p.got(_Assign) {
 		d.Values = p.exprList()
 	} else {
@@ -417,28 +385,31 @@ func (p *parser) varDecl(group *Group) Decl {
 	return d
 }
 
-var badRecv = new(Field) // to signal invalid receiver in funcDecl
-
-// FunctionDecl = "func" FunctionName ( Function | Signature ) | "func" AliasSpec .
+// FunctionDecl = "func" FunctionName ( Function | Signature ) .
 // FunctionName = identifier .
 // Function     = Signature FunctionBody .
 // MethodDecl   = "func" Receiver MethodName ( Function | Signature ) .
 // Receiver     = Parameters .
-func (p *parser) funcDecl() Decl {
+func (p *parser) funcDecl() *FuncDecl {
 	if trace {
 		defer p.trace("funcDecl")()
 	}
 
-	var recv *Field
+	f := new(FuncDecl)
+	f.init(p)
+
+	badRecv := false
 	if p.tok == _Lparen {
-		recv = badRecv
-		switch list := p.paramList(); len(list) {
+		rcvr := p.paramList()
+		switch len(rcvr) {
 		case 0:
 			p.error("method has no receiver")
+			badRecv = true
 		case 1:
-			recv = list[0]
+			f.Recv = rcvr[0]
 		default:
 			p.error("method has multiple receivers")
+			badRecv = true
 		}
 	}
 
@@ -448,11 +419,6 @@ func (p *parser) funcDecl() Decl {
 		return nil
 	}
 
-	name := p.name()
-	if recv == nil && p.got(_Rarrow) {
-		return p.aliasDecl(Func, name, nil)
-	}
-
 	// TODO(gri) check for regular functions only
 	// if name.Sym.Name == "init" {
 	// 	name = renameinit()
@@ -467,11 +433,7 @@ func (p *parser) funcDecl() Decl {
 	// 	}
 	// }
 
-	f := new(FuncDecl)
-	f.initFrom(&name.node) // TODO(gri) is this the correct position for methods?
-
-	f.Recv = recv
-	f.Name = name
+	f.Name = p.name()
 	f.Type = p.funcType()
 	if gcCompat {
 		f.node = f.Type.node
@@ -486,7 +448,7 @@ func (p *parser) funcDecl() Decl {
 	// 	p.error("can only use //go:noescape with external func implementations")
 	// }
 
-	if recv == badRecv {
+	if badRecv {
 		return nil // TODO(gri) better solution
 	}
 	return f
@@ -555,7 +517,7 @@ func (p *parser) unaryExpr() Expr {
 			return x
 		}
 
-	case _Larrow:
+	case _Arrow:
 		// receive op (<-x) or receive-only channel (<-chan E)
 		p.next()
 
@@ -969,7 +931,7 @@ func (p *parser) tryType() Expr {
 		p.next()
 		return indirect(p.type_())
 
-	case _Larrow:
+	case _Arrow:
 		// recvchantype
 		p.next()
 		p.want(_Chan)
@@ -1015,7 +977,7 @@ func (p *parser) tryType() Expr {
 		p.next()
 		t := new(ChanType)
 		t.init(p)
-		if p.got(_Larrow) {
+		if p.got(_Arrow) {
 			t.Dir = SendOnly
 		}
 		t.Elem = p.chanElem()
@@ -1358,7 +1320,7 @@ func (p *parser) paramDecl() *Field {
 	case _Name:
 		f.Name = p.name()
 		switch p.tok {
-		case _Name, _Star, _Larrow, _Func, _Lbrack, _Chan, _Map, _Struct, _Interface, _Lparen:
+		case _Name, _Star, _Arrow, _Func, _Lbrack, _Chan, _Map, _Struct, _Interface, _Lparen:
 			// sym name_or_type
 			f.Type = p.type_()
 
@@ -1373,7 +1335,7 @@ func (p *parser) paramDecl() *Field {
 			f.Name = nil
 		}
 
-	case _Larrow, _Star, _Func, _Lbrack, _Chan, _Map, _Struct, _Interface, _Lparen:
+	case _Arrow, _Star, _Func, _Lbrack, _Chan, _Map, _Struct, _Interface, _Lparen:
 		// name_or_type
 		f.Type = p.type_()
 
@@ -1507,7 +1469,7 @@ func (p *parser) simpleStmt(lhs Expr, rangeOk bool) SimpleStmt {
 			p.next()
 			return p.newAssignStmt(op, lhs, ImplicitOne)
 
-		case _Larrow:
+		case _Arrow:
 			// lhs <- rhs
 			p.next()
 			s := new(SendStmt)
@@ -1860,7 +1822,7 @@ func (p *parser) commClause() *CommClause {
 		p.next()
 		lhs := p.exprList()
 
-		if _, ok := lhs.(*ListExpr); !ok && p.tok == _Larrow {
+		if _, ok := lhs.(*ListExpr); !ok && p.tok == _Arrow {
 			// lhs <- x
 		} else {
 			// lhs
@@ -1940,7 +1902,7 @@ func (p *parser) stmt() Stmt {
 
 	case _Literal, _Func, _Lparen, // operands
 		_Lbrack, _Struct, _Map, _Chan, _Interface, // composite types
-		_Larrow: // receive operator
+		_Arrow: // receive operator
 		return p.simpleStmt(nil, false)
 
 	case _For: