the microsoft compiler platform (roslyn). a quick overview

The Microsoft Compiler PlatformJohnny Hooyberghs

johnny.hooyberghs@involved-it.be

@djohnnieke

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• May: no event• June

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The Microsoft Compiler PlatformJohnny Hooyberghs

johnny.hooyberghs@involved-it.be

@djohnnieke

I work for Involved-IT

A group of passionate software engineers who design, build and deliver software using .NET and the best bits of the Web

“

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agenda• Roslyn Overview• New C# 6 language features• Compiler API• syntax, compilation, symbols, data flow,

control flow

• Diagnostics and code fixes• Analyzers and NuGet• Scripting

The .NET Compiler Platform ("Roslyn") provides open-source C# and Visual Basic compilers with rich

code analysis APIs

It enables building code analysis tools with the same APIs that are

used by Visual Studio

roslyn overview• Rewrite of the VB and C# compilers• Written in C# and VB itself• Language services integrated in IDE• Intellisense• Code browsing experiences• Refactorings• ...

• Code analysis from managed languages• Build compilers and tools

why roslyn• Managed languages• Better productivity• New language features are easier to

implement• 1 compiler, different contexts• csc.exe, vbc.exe• Background compilers in IDE• Snippet compiler

• Support for experimentation and prototyping• Richer tooling, 3rd party extensions,

education

current compiler

compilerC#VB

IL

current compiler

parser symbols binder IL emitter

C#VB

IL

roslyn compiler

C#VB

ILSynta

x Tree API

Symbo

l API

Binding & Flow

Analysis API

Emit API

By rewriting the C# and VB compiler it becomes easier to implement new

language features

Smaller language features are finally worked on because of the smaller

impact

C# history

C# 1Managed

C# 2Generics

C# 3LINQ

C# 4Dynamic

programing

C# 5Asynchronous programing

C# 6Compilel Platform “Roslyn”

new C# 6 language features• Using static• Nameof operator• Property initializers• Constructor assignment to getter-only properties• Expression bodies• String interpolation• Null conditional• Index initializer• Exception filters• Await in catch/finally

compiler API – syntax • Textual representation of source code• Represented as a tree data structure• Built from a sequence of tokens

Console . WriteLine ( x ) ;

identifier dot open paren close paren semicolonidentifier identifier

compiler API – tokens• Identifiers• Console, Math, WriteLine, System, x, ...

• Keywords• if, static, class, return, ...

• Operators• +, *, &&, %, ...

• Punctuation• ., ;, ...

• Trivia• whitespace, comments

compiler API – constructs

• Declarations• Types, Members

• Statements• if( ... )

• Clauses• else( ... ), where flag

• Expressions• Invocations or expressions using operators

compiler API – trees

Console . WriteLine ( x ) ;

identifier dot open paren close parensemicolonidentifier identifier

WS CRLF

trivia trivia

SimpleMemberAccessExpression

IdentifierName

IdentifierName

InvocationExpression

ExpressionStatement

ArgumentList

Argument

IdentifierName

compiler API – compilation• Code compilation as a service• Based upon• Syntax tree• Compilation options• Metadata references

• Use Emit to write to a file• Compilation results including diagnostics• Semantic analysis

compiler API – symbols

• GetSemanticModel on a compilation• Get symbol information• Get speculative symbol information• Find the closest enclosing symbol from a

position• Check if symbols are accessible from a

position• Lookup symbols from a position• Getting constant values for literals

compiler API – flow analysis• Data flow analysis• How does data flow into and out of a region• Useful for Extract Method analysis

• Control flow analysis• How does control get transferred in and out

of a region• Reachability• Entry points• Exit point• Return statements

diagnostics and code fixes• Stylistic advice for source code• Like StyleCop rules• Implement your own rules• Supported in Visual Studio 2015

• Provide solutions to rule violations• Ligth bulb experience• Provides preview for code fixes

analyzers and NuGet• Creating a VSIX extension for Visual

Studio to distribute analyzers• Create a NuGet package to install

analyzers inside your projects• Distribute analyzers with your NuGet

packages, for example to accommodate your frameworks and API’s

scripting• Evaluate C# or VB expressions• Getting variables from scripts• Adding references and using namespaces• Dynamic support for scripts• Setting globals to pass data into a script• Creating a delegate from a script• REPL (read-eval-print-loop)

and we’re done

Johnny Hooyberghs

johnny.hooyberghs@involved-it.be

@djohnnieke