1 files changed, 79 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/noder/quirks.go b/src/cmd/compile/internal/noder/quirks.go
new file mode 100644
index 0000000..a22577f
--- /dev/null
+++ b/src/cmd/compile/internal/noder/quirks.go
@@ -0,0 +1,79 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package noder
+
+import (
+	"fmt"
+
+	"cmd/compile/internal/syntax"
+)
+
+// typeExprEndPos returns the position that noder would leave base.Pos
+// after parsing the given type expression.
+//
+// Deprecated: This function exists to emulate position semantics from
+// Go 1.17, necessary for compatibility with the backend DWARF
+// generation logic that assigns variables to their appropriate scope.
+func typeExprEndPos(expr0 syntax.Expr) syntax.Pos {
+	for {
+		switch expr := expr0.(type) {
+		case *syntax.Name:
+			return expr.Pos()
+		case *syntax.SelectorExpr:
+			return expr.X.Pos()
+
+		case *syntax.ParenExpr:
+			expr0 = expr.X
+
+		case *syntax.Operation:
+			assert(expr.Op == syntax.Mul)
+			assert(expr.Y == nil)
+			expr0 = expr.X
+
+		case *syntax.ArrayType:
+			expr0 = expr.Elem
+		case *syntax.ChanType:
+			expr0 = expr.Elem
+		case *syntax.DotsType:
+			expr0 = expr.Elem
+		case *syntax.MapType:
+			expr0 = expr.Value
+		case *syntax.SliceType:
+			expr0 = expr.Elem
+
+		case *syntax.StructType:
+			return expr.Pos()
+
+		case *syntax.InterfaceType:
+			expr0 = lastFieldType(expr.MethodList)
+			if expr0 == nil {
+				return expr.Pos()
+			}
+
+		case *syntax.FuncType:
+			expr0 = lastFieldType(expr.ResultList)
+			if expr0 == nil {
+				expr0 = lastFieldType(expr.ParamList)
+				if expr0 == nil {
+					return expr.Pos()
+				}
+			}
+
+		case *syntax.IndexExpr: // explicit type instantiation
+			targs := unpackListExpr(expr.Index)
+			expr0 = targs[len(targs)-1]
+
+		default:
+			panic(fmt.Sprintf("%s: unexpected type expression %v", expr.Pos(), syntax.String(expr)))
+		}
+	}
+}
+
+func lastFieldType(fields []*syntax.Field) syntax.Expr {
+	if len(fields) == 0 {
+		return nil
+	}
+	return fields[len(fields)-1].Type
+}