Shorten "if denotation is current the symbol" to "currentSymbol".

And make its usage more systematic on all substitutions where it makes sense.

2 files changed, 21 insertions, 6 deletions

diff --git a/src/dotty/tools/dotc/core/Substituters.scala b/src/dotty/tools/dotc/core/Substituters.scala
index c67d352a4..a7977dc2b 100644
--- a/src/dotty/tools/dotc/core/Substituters.scala
+++ b/src/dotty/tools/dotc/core/Substituters.scala
@@ -12,7 +12,7 @@ trait Substituters { this: Context =>
       case tp: BoundType =>
         if (tp.binder eq from) tp.copyBoundType(to.asInstanceOf[tp.BT]) else tp
       case tp: NamedType =>
-        if (tp.denotationIsCurrent && tp.symbol.isStatic) tp
+        if (tp.currentSymbol.isStatic) tp
         else tp.derivedSelect(subst(tp.prefix, from, to, theMap))
       case _: ThisType | NoPrefix =>
         tp
@@ -166,7 +166,7 @@ trait Substituters { this: Context =>
       case tp: ThisType =>
         if (tp.cls eq from) to else tp
       case tp: NamedType =>
-        if (tp.symbol.isStaticOwner) tp
+        if (tp.currentSymbol.isStaticOwner) tp
         else tp.derivedSelect(substThis(tp.prefix, from, to, theMap))
       case _: BoundType | NoPrefix =>
         tp
@@ -184,7 +184,7 @@ trait Substituters { this: Context =>
       case tp @ RefinedThis(rt) =>
         if (rt eq from) to else tp
       case tp: NamedType =>
-        if (tp.denotationIsCurrent && tp.symbol.isStatic) tp
+        if (tp.currentSymbol.isStatic) tp
         else tp.derivedSelect(substThis(tp.prefix, from, to, theMap))
       case _: ThisType | _: BoundType | NoPrefix =>
         tp
@@ -202,7 +202,7 @@ trait Substituters { this: Context =>
       case tp: BoundType =>
         if (tp == from) to else tp
       case tp: NamedType =>
-        if (tp.symbol.isStatic) tp
+        if (tp.currentSymbol.isStatic) tp
         else tp.derivedSelect(substParam(tp.prefix, from, to, theMap))
       case _: ThisType | NoPrefix =>
         tp
@@ -220,7 +220,7 @@ trait Substituters { this: Context =>
       case tp: ParamType =>
         if (tp.binder == from) to(tp.paramNum) else tp
       case tp: NamedType =>
-        if (tp.symbol.isStatic) tp
+        if (tp.currentSymbol.isStatic) tp
         else tp.derivedSelect(substParams(tp.prefix, from, to, theMap))
       case _: ThisType | NoPrefix | _: RefinedThis =>
         tp
diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index c2d465f7f..42ff62f4d 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -1102,9 +1102,24 @@ object Types {
     // (1) checkedPeriod != Nowhere  =>  lastDenotation != null
     // (2) lastDenotation != null    =>  lastSymbol != null
 
+    /** There is a denotation computed which is valid (somewhere in) the
+     *  current run.
+     */
     def denotationIsCurrent(implicit ctx: Context) =
       lastDenotation != null && lastDenotation.validFor.runId == ctx.runId
 
+    /** The the denotation is current, its symbol, otherwise NoDenotation.
+     *
+     *  Note: This operation does not force the denotation, and is therefore
+     *  timing dependent. It should only be used if the outcome of the
+     *  essential computation does not depend on the symbol being present or not.
+     *  It's currently used to take an optimized path in substituters and
+     *  type accumulators, as well as to be safe in diagnostiic printing.
+     *  Normally, it's better to use `symbol`, not `currentSymbol`.
+     */
+    def currentSymbol(implicit ctx: Context) =
+      if (denotationIsCurrent) symbol else NoSymbol
+
     /** The denotation currently denoted by this type */
     final def denot(implicit ctx: Context): Denotation = {
       val now = ctx.period
@@ -2659,7 +2674,7 @@ object Types {
           this(x, if (tp1.exists) tp1 else tp.prefix)
         }
       case tp: TermRef =>
-        if (stopAtStatic && tp.denotationIsCurrent && tp.symbol.isStatic) x
+        if (stopAtStatic && tp.currentSymbol.isStatic) x
         else this(x, tp.prefix)
 
       case _: ThisType