scala3-compiler-bootstrapped/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

Concise view

Type members

Classlikes

Attributes

Graph
Supertypes: trait Serializable
trait Product
trait Equals
class Test
class Object
trait Matchable
class Any

Attributes

Graph
Supertypes: trait Singleton
trait Product
trait Mirror
trait Serializable
trait Product
trait Equals
class Test
class Object
trait Matchable
class Any
Self type: GuardTest.type

Attributes

Graph
Supertypes: trait Serializable
trait Product
trait Equals
class Plan
class Object
trait Matchable
class Any

Attributes

Graph
Supertypes: trait Serializable
trait Product
trait Equals
class Test
class Object
trait Matchable
class Any

Attributes

Graph
Supertypes: trait Serializable
trait Product
trait Equals
class Plan
class Object
trait Matchable
class Any

Attributes

Graph
Supertypes: trait Singleton
trait Product
trait Mirror
trait Serializable
trait Product
trait Equals
class Test
class Object
trait Matchable
class Any
Self type: NonEmptyTest.type

Attributes

Graph
Supertypes: trait Singleton
trait Product
trait Mirror
trait Serializable
trait Product
trait Equals
class Test
class Object
trait Matchable
class Any
Self type: NonNullTest.type

The different kinds of plans

Attributes

Graph
Supertypes: class Object
trait Matchable
class Any
Known subtypes: class LabeledPlan
class LetPlan
class ResultPlan
class ReturnPlan
class SeqPlan
class TestPlan

A superclass for plan transforms

Attributes

Graph
Supertypes: trait Plan => Plan
class Object
trait Matchable
class Any

Attributes

Graph
Supertypes: trait Serializable
trait Product
trait Equals
class Plan
class Object
trait Matchable
class Any

Attributes

Graph
Supertypes: trait Serializable
trait Product
trait Equals
class Plan
class Object
trait Matchable
class Any

Attributes

Graph
Supertypes: trait Serializable
trait Product
trait Equals
class Plan
class Object
trait Matchable
class Any

The different kinds of tests

Attributes

Graph
Supertypes: class Object
trait Matchable
class Any
Known subtypes: class EqualTest
object GuardTest.type
class LengthTest
object NonEmptyTest.type
object NonNullTest.type
class TypeTest

Attributes

Companion:: object
Graph
Supertypes: trait Serializable
trait Product
trait Equals
class Plan
class Object
trait Matchable
class Any

Attributes

Companion:: class
Graph
Supertypes: trait Product
trait Mirror
class Object
trait Matchable
class Any
Self type: TestPlan.type

Attributes

Graph
Supertypes: trait Serializable
trait Product
trait Equals
class Test
class Object
trait Matchable
class Any

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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