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| 1 | +package dotty.tools.dotc |
| 2 | +package transform |
| 3 | + |
| 4 | +import dotty.tools.dotc.ast.Trees._ |
| 5 | +import dotty.tools.dotc.ast.{TreeTypeMap, tpd, untpd} |
| 6 | +import dotty.tools.dotc.core.Constants._ |
| 7 | +import dotty.tools.dotc.core.Contexts._ |
| 8 | +import dotty.tools.dotc.core.Decorators._ |
| 9 | +import dotty.tools.dotc.core.Flags._ |
| 10 | +import dotty.tools.dotc.core.quoted._ |
| 11 | +import dotty.tools.dotc.core.NameKinds._ |
| 12 | +import dotty.tools.dotc.core.StagingContext._ |
| 13 | +import dotty.tools.dotc.core.StdNames._ |
| 14 | +import dotty.tools.dotc.core.Symbols._ |
| 15 | +import dotty.tools.dotc.core.tasty.TreePickler.Hole |
| 16 | +import dotty.tools.dotc.core.Types._ |
| 17 | +import dotty.tools.dotc.util.SourcePosition |
| 18 | +import dotty.tools.dotc.util.Spans._ |
| 19 | +import dotty.tools.dotc.transform.SymUtils._ |
| 20 | +import dotty.tools.dotc.transform.TreeMapWithStages._ |
| 21 | +import dotty.tools.dotc.typer.Implicits.SearchFailureType |
| 22 | +import dotty.tools.dotc.typer.Inliner |
| 23 | + |
| 24 | +import scala.collection.mutable |
| 25 | +import dotty.tools.dotc.util.SourcePosition |
| 26 | + |
| 27 | +import scala.annotation.constructorOnly |
| 28 | + |
| 29 | +/** Checks that the Phase Consistency Principle (PCP) holds and heals types. |
| 30 | + * |
| 31 | + * Type healing consists in transforming a phase inconsistent type `T` into a splice of `implicitly[Type[T]]`. |
| 32 | + */ |
| 33 | +class PCPCheckAndHeal(@constructorOnly ictx: Context) extends TreeMapWithStages(ictx) { |
| 34 | + import tpd._ |
| 35 | + |
| 36 | + override def transform(tree: Tree)(implicit ctx: Context): Tree = tree match { |
| 37 | + case tree: DefDef if tree.symbol.is(Inline) && level > 0 => EmptyTree |
| 38 | + case _ => checkLevel(super.transform(tree)) |
| 39 | + } |
| 40 | + |
| 41 | + /** Transform quoted trees while maintaining phase correctness */ |
| 42 | + override protected def transformQuotation(body: Tree, quote: Tree)(implicit ctx: Context): Tree = { |
| 43 | + val body1 = transform(body)(quoteContext) |
| 44 | + super.transformQuotation(body1, quote) |
| 45 | + } |
| 46 | + |
| 47 | + /** Transform splice |
| 48 | + * - If inside a quote, transform the contents of the splice. |
| 49 | + * - If inside inlined code, expand the macro code. |
| 50 | + * - If inside of a macro definition, check the validity of the macro. |
| 51 | + */ |
| 52 | + protected def transformSplice(splice: Select)(implicit ctx: Context): Tree = { |
| 53 | + if (level >= 1) { |
| 54 | + val body1 = transform(splice.qualifier)(spliceContext) |
| 55 | + val splice1 = cpy.Select(splice)(body1, splice.name) |
| 56 | + if (splice1.isType) splice1 |
| 57 | + else addSpliceCast(splice1) |
| 58 | + } |
| 59 | + else { |
| 60 | + assert(!enclosingInlineds.nonEmpty, "unexpanded macro") |
| 61 | + assert(ctx.owner.isInlineMethod) |
| 62 | + if (Splicer.canBeSpliced(splice.qualifier)) { // level 0 inside an inline definition |
| 63 | + transform(splice.qualifier)(spliceContext) // Just check PCP |
| 64 | + splice |
| 65 | + } |
| 66 | + else { // level 0 inside an inline definition |
| 67 | + ctx.error( |
| 68 | + "Malformed macro call. The contents of the splice ${...} must call a static method and arguments must be quoted or inline.", |
| 69 | + splice.sourcePos) |
| 70 | + splice |
| 71 | + } |
| 72 | + } |
| 73 | + } |
| 74 | + |
| 75 | + |
| 76 | + /** Add cast to force boundaries where T and $t (an alias of T) are used to ensure PCP. |
| 77 | + * '{ ${...: T} } --> '{ ${...: T}.asInstanceOf[T] } --> '{ ${...: T}.asInstanceOf[$t] } |
| 78 | + */ |
| 79 | + protected def addSpliceCast(tree: Tree)(implicit ctx: Context): Tree = { |
| 80 | + val tp = checkType(tree.sourcePos).apply(tree.tpe.widenTermRefExpr) |
| 81 | + tree.cast(tp).withSpan(tree.span) |
| 82 | + } |
| 83 | + |
| 84 | + /** If `tree` refers to a locally defined symbol (either directly, or in a pickled type), |
| 85 | + * check that its staging level matches the current level. References to types |
| 86 | + * that are phase-incorrect can still be healed as follows: |
| 87 | + * |
| 88 | + * If `T` is a reference to a type at the wrong level, try to heal it by replacing it with |
| 89 | + * `${implicitly[quoted.Type[T]]}`. |
| 90 | + */ |
| 91 | + protected def checkLevel(tree: Tree)(implicit ctx: Context): Tree = { |
| 92 | + def checkTp(tp: Type): Type = checkType(tree.sourcePos).apply(tp) |
| 93 | + tree match { |
| 94 | + case Quoted(_) | Spliced(_) => |
| 95 | + tree |
| 96 | + case tree: RefTree if tree.symbol.is(InlineParam) => |
| 97 | + tree |
| 98 | + case _: This => |
| 99 | + assert(checkSymLevel(tree.symbol, tree.tpe, tree.sourcePos).isEmpty) |
| 100 | + tree |
| 101 | + case _: Ident => |
| 102 | + checkSymLevel(tree.symbol, tree.tpe, tree.sourcePos) match { |
| 103 | + case Some(tpRef) => tpRef |
| 104 | + case _ => tree |
| 105 | + } |
| 106 | + case _: TypeTree | _: AppliedTypeTree | _: Apply | _: TypeApply | _: UnApply | Select(_, OuterSelectName(_, _)) => |
| 107 | + tree.withType(checkTp(tree.tpe)) |
| 108 | + case _: ValOrDefDef | _: Bind => |
| 109 | + tree.symbol.info = checkTp(tree.symbol.info) |
| 110 | + tree |
| 111 | + case _: Template => |
| 112 | + checkTp(tree.symbol.owner.asClass.givenSelfType) |
| 113 | + tree |
| 114 | + case _ => |
| 115 | + tree |
| 116 | + } |
| 117 | + } |
| 118 | + |
| 119 | + /** Check and heal all named types and this-types in a given type for phase consistency. */ |
| 120 | + private def checkType(pos: SourcePosition)(implicit ctx: Context): TypeMap = new TypeMap { |
| 121 | + def apply(tp: Type): Type = reporting.trace(i"check type level $tp at $level") { |
| 122 | + tp match { |
| 123 | + case tp: TypeRef if tp.symbol.isSplice => |
| 124 | + if (tp.isTerm) |
| 125 | + ctx.error(i"splice outside quotes", pos) |
| 126 | + tp |
| 127 | + case tp: NamedType => |
| 128 | + checkSymLevel(tp.symbol, tp, pos) match { |
| 129 | + case Some(tpRef) => tpRef.tpe |
| 130 | + case _ => |
| 131 | + if (tp.symbol.is(Param)) tp |
| 132 | + else mapOver(tp) |
| 133 | + } |
| 134 | + case tp: ThisType => |
| 135 | + assert(checkSymLevel(tp.cls, tp, pos).isEmpty) |
| 136 | + mapOver(tp) |
| 137 | + case _ => |
| 138 | + mapOver(tp) |
| 139 | + } |
| 140 | + } |
| 141 | + } |
| 142 | + |
| 143 | + /** Check reference to `sym` for phase consistency, where `tp` is the underlying type |
| 144 | + * by which we refer to `sym`. If it is an inconsistent type try construct a healed type for it. |
| 145 | + * |
| 146 | + * @return `None` if the phase is correct or cannot be healed |
| 147 | + * `Some(tree)` with the `tree` of the healed type tree for `${implicitly[quoted.Type[T]]}` |
| 148 | + */ |
| 149 | + private def checkSymLevel(sym: Symbol, tp: Type, pos: SourcePosition)(implicit ctx: Context): Option[Tree] = { |
| 150 | + /** Is a reference to a class but not `this.type` */ |
| 151 | + def isClassRef = sym.isClass && !tp.isInstanceOf[ThisType] |
| 152 | + |
| 153 | + if (sym.exists && !sym.isStaticOwner && !isClassRef && !levelOK(sym)) |
| 154 | + tryHeal(sym, tp, pos) |
| 155 | + else |
| 156 | + None |
| 157 | + } |
| 158 | + |
| 159 | + /** Does the level of `sym` match the current level? |
| 160 | + * An exception is made for inline vals in macros. These are also OK if their level |
| 161 | + * is one higher than the current level, because on execution such values |
| 162 | + * are constant expression trees and we can pull out the constant from the tree. |
| 163 | + */ |
| 164 | + private def levelOK(sym: Symbol)(implicit ctx: Context): Boolean = levelOf(sym) match { |
| 165 | + case Some(l) => |
| 166 | + l == level || |
| 167 | + level == -1 && ( |
| 168 | + sym == defn.TastyReflection_macroContext || |
| 169 | + // here we assume that Splicer.canBeSpliced was true before going to level -1, |
| 170 | + // this implies that all non-inline arguments are quoted and that the following two cases are checked |
| 171 | + // on inline parameters or type parameters. |
| 172 | + sym.is(Param) || |
| 173 | + sym.isClass // reference to this in inline methods |
| 174 | + ) |
| 175 | + case None => |
| 176 | + !sym.is(Param) || levelOK(sym.owner) |
| 177 | + } |
| 178 | + |
| 179 | + /** Try to heal phase-inconsistent reference to type `T` using a local type definition. |
| 180 | + * @return None if successful |
| 181 | + * @return Some(msg) if unsuccessful where `msg` is a potentially empty error message |
| 182 | + * to be added to the "inconsistent phase" message. |
| 183 | + */ |
| 184 | + protected def tryHeal(sym: Symbol, tp: Type, pos: SourcePosition)(implicit ctx: Context): Option[Tree] = { |
| 185 | + def levelError(errMsg: String) = { |
| 186 | + def symStr = |
| 187 | + if (!tp.isInstanceOf[ThisType]) sym.show |
| 188 | + else if (sym.is(ModuleClass)) sym.sourceModule.show |
| 189 | + else i"${sym.name}.this" |
| 190 | + ctx.error( |
| 191 | + em"""access to $symStr from wrong staging level: |
| 192 | + | - the definition is at level ${levelOf(sym).getOrElse(0)}, |
| 193 | + | - but the access is at level $level.$errMsg""", pos) |
| 194 | + None |
| 195 | + } |
| 196 | + tp match { |
| 197 | + case tp: TypeRef => |
| 198 | + if (level == -1) { |
| 199 | + assert(ctx.inInlineMethod) |
| 200 | + None |
| 201 | + } else { |
| 202 | + val reqType = defn.QuotedTypeType.appliedTo(tp) |
| 203 | + val tag = ctx.typer.inferImplicitArg(reqType, pos.span) |
| 204 | + tag.tpe match { |
| 205 | + case fail: SearchFailureType => |
| 206 | + levelError(i""" |
| 207 | + | |
| 208 | + | The access would be accepted with the right type tag, but |
| 209 | + | ${ctx.typer.missingArgMsg(tag, reqType, "")}""") |
| 210 | + case _ => |
| 211 | + Some(tag.select(tpnme.splice)) |
| 212 | + } |
| 213 | + } |
| 214 | + case _ => |
| 215 | + levelError("") |
| 216 | + } |
| 217 | + } |
| 218 | + |
| 219 | +} |
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