[dev.typeparams] cmd/compile: handle objStub earlier in reader

There's no point in reading the object dictionary for a stub
declaration. Only the package that contains the full object definition
will contain an object dictionary.

Change-Id: I458b77d20745105bf46190ef552312bdb5ca4d06
Reviewed-on: https://go-review.googlesource.com/c/go/+/334409
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>

1 files changed, 20 insertions, 18 deletions

diff --git a/src/cmd/compile/internal/noder/reader.go b/src/cmd/compile/internal/noder/reader.go
index 25aac6c026..2351d1d0ba 100644
--- a/src/cmd/compile/internal/noder/reader.go
+++ b/src/cmd/compile/internal/noder/reader.go
@@ -520,14 +520,22 @@ func (pr *pkgReader) objIdx(idx int, implicits, explicits []*types.Type) ir.Node
 
 	r.typeParamBounds(sym, implicits, explicits)
 
-	origSym := sym
-
-	sym = r.mangle(sym)
-	if !sym.IsBlank() && sym.Def != nil {
-		return sym.Def.(ir.Node)
-	}
-
 	tag := codeObj(r.code(syncCodeObj))
+	if tag == objStub {
+		assert(!sym.IsBlank())
+		switch sym.Pkg {
+		case types.BuiltinPkg, ir.Pkgs.Unsafe:
+			return sym.Def.(ir.Node)
+		}
+		if pri, ok := objReader[sym]; ok {
+			return pri.pr.objIdx(pri.idx, nil, explicits)
+		}
+		if haveLegacyImports {
+			assert(!r.hasTypeParams())
+			return typecheck.Resolve(ir.NewIdent(src.NoXPos, sym))
+		}
+		base.Fatalf("unresolved stub: %v", sym)
+	}
 
 	{
 		rdict := pr.newReader(relocObjDict, idx, syncObject1)
@@ -538,6 +546,11 @@ func (pr *pkgReader) objIdx(idx int, implicits, explicits []*types.Type) ir.Node
 		}
 	}
 
+	sym = r.mangle(sym)
+	if !sym.IsBlank() && sym.Def != nil {
+		return sym.Def.(*ir.Name)
+	}
+
 	do := func(op ir.Op, hasTParams bool) *ir.Name {
 		pos := r.pos()
 		if hasTParams {
@@ -560,17 +573,6 @@ func (pr *pkgReader) objIdx(idx int, implicits, explicits []*types.Type) ir.Node
 	default:
 		panic("unexpected object")
 
-	case objStub:
-		if pri, ok := objReader[origSym]; ok {
-			return pri.pr.objIdx(pri.idx, nil, explicits)
-		}
-		if haveLegacyImports {
-			assert(!r.hasTypeParams())
-			return typecheck.Resolve(ir.NewIdent(src.NoXPos, origSym))
-		}
-		base.Fatalf("unresolved stub: %v", origSym)
-		panic("unreachable")
-
 	case objAlias:
 		name := do(ir.OTYPE, false)
 		r.setType(name, r.typ())