Ensure trait var accessor type is widened

adriaanm · adriaanm · commit ab61fedaaab3 · 2016-08-29T18:18:35.000+02:00
If we don't widen, we'll fail to find the setter when
typing `x = 42`, because `x` is constant-folded to `0`,
as its type is `=&gt; Int(0)`. After widening, `x` is
type checked to `x` and its symbol is the getter in the
trait, which can then be rewritten to the setter.

Regression spotted and test case by szeiger.
diff --git a/src/compiler/scala/tools/nsc/typechecker/Namers.scala b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
@@ -952,7 +952,8 @@ trait Namers extends MethodSynthesis {
            !tpe.typeSymbolDirect.isModuleClass // Infer Foo.type instead of "object Foo"
         && (tpe.widen <:< pt)                  // Don't widen our way out of conforming to pt
         && (   sym.isVariable
-            || sym.isMethod && !sym.hasAccessorFlag
+            || sym.hasFlag(ACCESSOR) && !sym.hasFlag(STABLE)
+            || sym.isMethod && !sym.hasFlag(ACCESSOR)
             || isHidden(tpe)
            )
       )
diff --git a/test/files/pos/fields_widen_trait_var.scala b/test/files/pos/fields_widen_trait_var.scala
@@ -0,0 +1,2 @@
+// check that the var below is assigned Int, and that we can assign to it
+trait C { protected final var x = 0; x = 42 }

Original file line number	Diff line number	Diff line change
`@@ -952,7 +952,8 @@ trait Namers extends MethodSynthesis {`
`952`	`952`	`!tpe.typeSymbolDirect.isModuleClass // Infer Foo.type instead of "object Foo"`
`953`	`953`	`&& (tpe.widen <:< pt) // Don't widen our way out of conforming to pt`
`954`	`954`	`&& ( sym.isVariable`
`955`		`- \|\| sym.isMethod && !sym.hasAccessorFlag`
	`955`	`+ \|\| sym.hasFlag(ACCESSOR) && !sym.hasFlag(STABLE)`
	`956`	`+ \|\| sym.isMethod && !sym.hasFlag(ACCESSOR)`
`956`	`957`	`\|\| isHidden(tpe)`
`957`	`958`	`)`
`958`	`959`	`)`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+// check that the var below is assigned Int, and that we can assign to it`
	`2`	`+trait C { protected final var x = 0; x = 42 }`