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Don't compute least upper bounds for expressions in statement positio…

…ns inside blocks.

This may save huge amount of time (Fixes SI-5862) for complicated lubs. I had to remove the a check in adapt for
the part that transforms <expr> into { <expr>; () } when the expected type is Unit. The reason is in the
code.

As a side effect, we get more warnings for pure expressions in statement positions (see the change in the test file).
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dragos committed Jun 1, 2012
1 parent 71006c0 commit 037d3dcbc5896864aec0f9121eeda23fcc4cd610
@@ -86,6 +86,17 @@ trait Modes {
*/
final val TYPEPATmode = 0x10000
/** STATmode is set when typing statements inside a block.
*
* This is useful only for skipping lub computations in
* such positions, when the expected type is known to be Unit. This
* saves time in pathological cases where lubs can take many seconds
* but in the end is discarded.
*
* TODO: Remove when lubs become types in their own right.
*/
final val STATmode = 0x20000
final private val StickyModes = EXPRmode | PATTERNmode | TYPEmode | ALTmode
final def onlyStickyModes(mode: Int) =
@@ -128,7 +139,8 @@ trait Modes {
(1 << 13) -> "ALTmode",
(1 << 14) -> "HKmode",
(1 << 15) -> "BYVALmode",
(1 << 16) -> "TYPEPATmode"
(1 << 16) -> "TYPEPATmode",
(1 << 17) -> "STATmode"
)
def modeString(mode: Int): String =
if (mode == 0) "NOmode"
@@ -1127,9 +1127,11 @@ trait Typers extends Modes with Adaptations with Taggings {
if (inExprModeButNot(mode, FUNmode)) {
pt.normalize match {
case TypeRef(_, sym, _) =>
// note: was if (pt.typeSymbol == UnitClass) but this leads to a potentially
// infinite expansion if pt is constant type ()
if (sym == UnitClass && tree.tpe <:< AnyClass.tpe) { // (12)
// note: there was an additional '&& tree.tpe <:< AnyClass.tpe', claiming that
// it would save us from a potentially infinite expansion if pt is constant type ()
// didn't seem to do any good, and the test would miss the fact that Object.tpe <:< AnyClass.tpe
// after erasure (triggered by try-catches added by cleanup for structural types)
if (sym == UnitClass) { // (12)
if (settings.warnValueDiscard.value)
context.unit.warning(tree.pos, "discarded non-Unit value")
return typed(atPos(tree.pos)(Block(List(tree), Literal(Constant()))), mode, pt)
@@ -2566,7 +2568,7 @@ trait Typers extends Modes with Adaptations with Taggings {
} else newTyper(context.make(stat, exprOwner))
// XXX this creates a spurious dead code warning if an exception is thrown
// in a constructor, even if it is the only thing in the constructor.
val result = checkDead(localTyper.typed(stat, EXPRmode | BYVALmode, WildcardType))
val result = checkDead(localTyper.typed(stat, EXPRmode | BYVALmode | STATmode, WildcardType))
if (treeInfo.isSelfOrSuperConstrCall(result)) {
context.inConstructorSuffix = true
@@ -3861,6 +3863,7 @@ trait Typers extends Modes with Adaptations with Taggings {
&& thenTp =:= elseTp
) (thenp1.tpe, false) // use unpacked type
// TODO: skolemize (lub of packed types) when that no longer crashes on files/pos/t4070b.scala
else if ((mode & STATmode) != 0) (definitions.UnitClass.tpe, true)
else ptOrLub(List(thenp1.tpe, elsep1.tpe), pt)
if (needAdapt) { //isNumericValueType(owntype)) {
@@ -4744,7 +4747,7 @@ trait Typers extends Modes with Adaptations with Taggings {
var catches1 = typedCases(catches, ThrowableClass.tpe, pt)
val finalizer1 = if (finalizer.isEmpty) finalizer
else typed(finalizer, UnitClass.tpe)
val (owntype, needAdapt) = ptOrLub(block1.tpe :: (catches1 map (_.tpe)), pt)
val (owntype, needAdapt) = if ((mode & STATmode) != 0) (definitions.UnitClass.tpe, true) else ptOrLub(block1.tpe :: (catches1 map (_.tpe)), pt)
if (needAdapt) {
block1 = adapt(block1, mode, owntype)
catches1 = catches1 map (adaptCase(_, mode, owntype))
@@ -77,8 +77,8 @@ checksensible.scala:63: error: comparing a fresh object using `!=' will always y
new Exception() != new Exception()
^
checksensible.scala:66: error: comparing values of types Int and Null using `==' will always yield false
if (foo.length == null) "plante" else "plante pas"
^
val dummy = if (foo.length == null) "plante" else "plante pas"
^
checksensible.scala:71: error: comparing values of types Bip and Bop using `==' will always yield false
(x1 == x2)
^
@@ -63,7 +63,7 @@ class EqEqRefTest {
new Exception() != new Exception()
val foo: Array[String] = Array("1","2","3")
if (foo.length == null) "plante" else "plante pas"
val dummy = if (foo.length == null) "plante" else "plante pas"
// final classes with default equals
val x1 = new Bip

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