scala3-compiler-bootstrapped/dotty.tools/dotty.tools.dotc/dotty.tools.dotc.transform/PatternMatcher/Translator

Translator

dotty.tools.dotc.transform.PatternMatcher.Translator

class Translator(resultType: Type, thisPhase: MiniPhase)(using x$3: Context)

The pattern matching translator. Its general structure is a pipeline:

Match tree ---matchPlan---> Plan ---optimize---> Plan ---emit---> Tree

The pipeline consists of three steps:

build a plan, using methods matchPlan, caseDefPlan, patternPlan.
optimize the plan, using methods listed in optimization,
emit the translated tree, using methods emit, collectSwitchCases, emitSwitchCases, and emitCondition.

A plan represents the underlying decision graph. It consists of tests, let bindings, labeled blocks, return from said labeled blocks and code blocks. It's represented by its own data type. Plans are optimized by merging common tests and eliminating dead code.

Attributes

Graph
Supertypes: class Object

trait Matchable

class Any

Members list

Type members

Classlikes

Attributes

Supertypes: trait Serializable

trait Product

trait Equals

class Test

class Object

trait Matchable

class Any
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Attributes

Supertypes: trait Singleton

trait Product

trait Mirror

trait Serializable

trait Product

trait Equals

class Test

class Object

trait Matchable

class Any
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Self type: GuardTest.type

Attributes

Supertypes: trait Serializable

trait Product

trait Equals

class Plan

class Object

trait Matchable

class Any
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Attributes

Supertypes: trait Serializable

trait Product

trait Equals

class Test

class Object

trait Matchable

class Any
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Attributes

Supertypes: trait Serializable

trait Product

trait Equals

class Plan

class Object

trait Matchable

class Any
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Attributes

Supertypes: trait Singleton

trait Product

trait Mirror

trait Serializable

trait Product

trait Equals

class Test

class Object

trait Matchable

class Any
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Self type: NonEmptyTest.type

Attributes

Supertypes: trait Singleton

trait Product

trait Mirror

trait Serializable

trait Product

trait Equals

class Test

class Object

trait Matchable

class Any
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Self type: NonNullTest.type

The different kinds of plans

Attributes

Supertypes: class Object

trait Matchable

class Any
Known subtypes: class LabeledPlan

class LetPlan

class ResultPlan

class ReturnPlan

class SeqPlan

class TestPlan
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A superclass for plan transforms

Attributes

Supertypes: trait Plan => Plan

class Object

trait Matchable

class Any

Attributes

Supertypes: trait Serializable

trait Product

trait Equals

class Plan

class Object

trait Matchable

class Any
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Attributes

Supertypes: trait Serializable

trait Product

trait Equals

class Plan

class Object

trait Matchable

class Any
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Attributes

Supertypes: trait Serializable

trait Product

trait Equals

class Plan

class Object

trait Matchable

class Any
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The different kinds of tests

Attributes

Supertypes: class Object

trait Matchable

class Any
Known subtypes: class EqualTest

object GuardTest

class LengthTest

object NonEmptyTest

object NonNullTest

class TypeTest
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Attributes

Companion: object
Supertypes: trait Serializable

trait Product

trait Equals

class Plan

class Object

trait Matchable

class Any
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Attributes

Companion: class
Supertypes: trait Product

trait Mirror

class Object

trait Matchable

class Any
Self type: TestPlan.type

Attributes

Supertypes: trait Serializable

trait Product

trait Equals

class Test

class Object

trait Matchable

class Any
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Value members

Concrete methods

Merge identical consecutive tests.

When we have the following shape:

if (testA) plan1 if (testA) plan2 nextPlan?

transform it to

if (testA) { plan1 plan2 } nextPlan?

Similarly, when we have equivalent let bindings:

let x1 = rhs1 in plan1 let x2 = rhs2 in plan2 nextPlan?

and rhs1 and rhs2 are equivalent, transform it to

let x1 = rhs1 in { plan1 plan2[x1/x2] }

where plan2[x1/x2] means substituting x1 for x2 in plan2.

There are some tricks to "ignore" non-patmat-generated let bindings, i.e., captures written in the source code, while identifying common subplans.

Attributes

Pretty-print plan; used for debugging

Attributes

Translate pattern match to sequence of tests.

Attributes

Concrete fields

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