From 652cce0b0ad1b8b54f54a5d78a6c4defbd599124 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Fri, 14 Oct 2016 15:11:48 +0200
Subject: Fix #1570: Allow inline parameters as inline args

Inline parameters can always be passed to other
inline parameters.

Fixes #1570.
---
 src/dotty/tools/dotc/core/Flags.scala     |  3 +++
 src/dotty/tools/dotc/typer/Checking.scala | 11 +++++++----
 tests/pos/i1570.scala                     |  4 ++++
 3 files changed, 14 insertions(+), 4 deletions(-)
 create mode 100644 tests/pos/i1570.scala

diff --git a/src/dotty/tools/dotc/core/Flags.scala b/src/dotty/tools/dotc/core/Flags.scala
index 3f4433708..63fbc98dc 100644
--- a/src/dotty/tools/dotc/core/Flags.scala
+++ b/src/dotty/tools/dotc/core/Flags.scala
@@ -544,6 +544,9 @@ object Flags {
   /** An inline method */
   final val InlineMethod = allOf(Inline, Method)
 
+  /** An inline parameter */
+  final val InlineParam = allOf(Inline, Param)
+
   /** A parameter or parameter accessor */
   final val ParamOrAccessor = Param | ParamAccessor
 
diff --git a/src/dotty/tools/dotc/typer/Checking.scala b/src/dotty/tools/dotc/typer/Checking.scala
index 7899174f5..3ebae733f 100644
--- a/src/dotty/tools/dotc/typer/Checking.scala
+++ b/src/dotty/tools/dotc/typer/Checking.scala
@@ -482,10 +482,13 @@ trait Checking {
 
   /** Check that `tree` is a pure expression of constant type */
   def checkInlineConformant(tree: Tree, what: => String)(implicit ctx: Context): Unit =
-    tree.tpe.widenTermRefExpr match {
-      case tp: ConstantType if isPureExpr(tree) => // ok
-      case tp if defn.isFunctionType(tp) && isPureExpr(tree) => // ok
-      case _ => ctx.error(em"$what must be a constant expression or a function", tree.pos)
+    tree.tpe match {
+      case tp: TermRef if tp.symbol.is(InlineParam) => // ok
+      case tp => tp.widenTermRefExpr match {
+        case tp: ConstantType if isPureExpr(tree) => // ok
+        case tp if defn.isFunctionType(tp) && isPureExpr(tree) => // ok
+        case _ => ctx.error(em"$what must be a constant expression or a function", tree.pos)
+      }
     }
 
   /** Check that class does not define same symbol twice */
diff --git a/tests/pos/i1570.scala b/tests/pos/i1570.scala
new file mode 100644
index 000000000..c2e4fd01b
--- /dev/null
+++ b/tests/pos/i1570.scala
@@ -0,0 +1,4 @@
+object Test {
+  inline def foo(inline n: Int) = bar(n)
+  inline def bar(inline n: Int) = n
+}
-- 
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