Implement function-declaration in lib/Syntax

https://bugs.swift.org/browse/SR-4043

include/swift/Syntax/DeclSyntax.h

@@ -18,7 +18,6 @@
 #ifndef SWIFT_SYNTAX_DECLSYNTAX_H
 #define SWIFT_SYNTAX_DECLSYNTAX_H
 
-#include "swift/Syntax/GenericSyntax.h"
 #include "swift/Syntax/References.h"
 #include "swift/Syntax/RawSyntax.h"
 #include "swift/Syntax/Syntax.h"
@@ -35,6 +34,15 @@ namespace syntax {
 
 class ExprSyntax;
 class ExprSyntaxData;
+class CodeBlockStmtSyntax;
+class CodeBlockStmtSyntaxData;
+class TypeAttributesSyntax;
+class TypeAttributesSyntaxData;
+class DeclModifierListSyntax;
+class GenericWhereClauseSyntax;
+class GenericWhereClauseSyntaxData;
+class GenericParameterListSyntax;
+class GenericParameterListSyntaxData;
 
 #pragma mark declaration-modifier Data
 
@@ -154,6 +162,7 @@ class DeclModifierListSyntax final :
   friend struct SyntaxFactory;
   friend class Syntax;
   friend class SyntaxData;
+  friend class FunctionDeclSyntax;
 
   using DataType = DeclModifierListSyntaxData;
   static constexpr SyntaxKind Kind = SyntaxKind::DeclModifierList;
@@ -770,6 +779,115 @@ public:
   }
 };
 
+#pragma mark - function-declaration Data
+
+class FunctionDeclSyntaxData final : public SyntaxData {
+  friend struct SyntaxFactory;
+  friend class SyntaxData;
+  friend class FunctionDeclSyntax;
+
+  RC<TypeAttributesSyntaxData> CachedAttributes;
+  RC<DeclModifierListSyntaxData> CachedModifiers;
+  RC<GenericParameterClauseSyntaxData> CachedGenericParams;
+  RC<FunctionSignatureSyntaxData> CachedSignature;
+  RC<GenericWhereClauseSyntaxData> CachedGenericWhereClause;
+  RC<CodeBlockStmtSyntaxData> CachedBody;
+
+  FunctionDeclSyntaxData(const RC<RawSyntax> Raw,
+                         const SyntaxData *Parent = nullptr,
+                         const CursorIndex IndexInParent = 0);
+
+  static RC<FunctionDeclSyntaxData> make(const RC<RawSyntax> Raw,
+                                         const SyntaxData *Parent = nullptr,
+                                         const CursorIndex IndexInParent = 0);
+  static RC<FunctionDeclSyntaxData> makeBlank();
+
+public:
+  static bool classof(const SyntaxData *SD) {
+    return SD->getKind() == SyntaxKind::FunctionDecl;
+  }
+};
+
+#pragma mark - function-declaration API
+
+class FunctionDeclSyntax final : public Syntax {
+  friend struct SyntaxFactory;
+  friend class Syntax;
+  friend class SyntaxData;
+  friend class FunctionDeclSyntaxData;
+
+  enum class Cursor : CursorIndex {
+    Attributes,
+    Modifiers,
+    FuncKeyword,
+    Identifier,
+    GenericParameterClause,
+    Signature,
+    GenericWhereClause,
+    Body
+  };
+
+  using DataType = FunctionDeclSyntaxData;
+
+  FunctionDeclSyntax(const RC<SyntaxData> Root, const DataType *Data)
+    : Syntax(Root, Data) {}
+
+public:
+  /// Get the attributes of this function declaration.
+  TypeAttributesSyntax getAttributes() const;
+
+  /// Return a FunctionDeclSyntax with the given attributes.
+  FunctionDeclSyntax withAttributes(TypeAttributesSyntax NewAttributes) const;
+
+  /// Get the modifiers of this function declaration.
+  DeclModifierListSyntax getModifiers() const;
+
+  /// Return a FunctionDeclSyntax with the given modifiers.
+  FunctionDeclSyntax withModifiers(DeclModifierListSyntax NewModifiers) const;
+
+  /// Return the 'func' keyword of tis function declaration.
+  RC<TokenSyntax> getFuncKeyword() const;
+
+  /// Return a FunctionDeclSyntax with the given 'func' keyword.
+  FunctionDeclSyntax withFuncKeyword(RC<TokenSyntax> NewFuncKeyword) const;
+
+  /// Return the identifier of the function declaration.
+  RC<TokenSyntax> getIdentifier() const;
+
+  /// Return a FunctionDeclSyntax with the given identifier.
+  FunctionDeclSyntax withIdentifier(RC<TokenSyntax> NewIdentifier) const;
+
+  /// Return the generic parameter clause of the function declaration, if
+  /// there is one. Otherwise, return llvm::None.
+  llvm::Optional<GenericParameterClauseSyntax>
+  getGenericParameterClause() const;
+
+  /// Return a FunctionDeclSyntax with the given generic parameter clause.
+  /// To remove the generic parameters, pass in llvm::None.
+  FunctionDeclSyntax withGenericParameterClause(
+    llvm::Optional<GenericParameterClauseSyntax> NewGenericParams) const;
+
+  /// Return the signature of the function declaration.
+  FunctionSignatureSyntax getSignature() const;
+
+  /// Return a FunctionDeclSyntax with the given function signature.
+  FunctionDeclSyntax withSignature(FunctionSignatureSyntax NewSignature) const;
+
+  /// Return the body of the function declaration, if there is one.
+  ///
+  /// As an example, function declarations in protocols have no body.
+  llvm::Optional<CodeBlockStmtSyntax> getBody() const;
+
+  /// Return a FunctionDeclSyntax with the given body. To remove the body,
+  /// pass in llvm::None.
+  FunctionDeclSyntax
+  withBody(llvm::Optional<CodeBlockStmtSyntax> NewBody) const;
+
+  static bool classof(const Syntax *S) {
+    return S->getKind() == SyntaxKind::FunctionDecl;
+  }
+};
+
 } // end namespace syntax
 } // end namespace swift
 

include/swift/Syntax/GenericSyntax.h

@@ -277,9 +277,9 @@ class GenericParameterClauseSyntaxData final : public SyntaxData {
 
   RC<GenericParameterListSyntaxData> CachedGenericParameterList;
 
-  GenericParameterClauseSyntaxData(RC<RawSyntax> Raw,
+  GenericParameterClauseSyntaxData(const RC<RawSyntax> Raw,
                                    const SyntaxData *Parent = nullptr,
-                                   CursorIndex IndexInParent = 0);
+                                   const CursorIndex IndexInParent = 0);
   static RC<GenericParameterClauseSyntaxData>
   make(RC<RawSyntax> Raw,
        const SyntaxData *Parent = nullptr,
@@ -299,6 +299,8 @@ class GenericParameterClauseSyntax final : public Syntax {
   friend struct SyntaxFactory;
   friend class GenericParameterClauseSyntaxData;
   friend class GenericParameterClauseBuilder;
+  friend class FunctionDeclSyntax;
+
   enum class Cursor : CursorIndex {
     LeftAngleBracketToken,
     GenericParameterList,

include/swift/Syntax/Rewriter.h

@@ -24,6 +24,7 @@
 
 #include "swift/Syntax/References.h"
 #include "swift/Syntax/DeclSyntax.h"
+#include "swift/Syntax/GenericSyntax.h"
 #include "swift/Syntax/ExprSyntax.h"
 #include "swift/Syntax/StmtSyntax.h"
 #include "swift/Syntax/Syntax.h"

include/swift/Syntax/StmtSyntax.h

@@ -130,6 +130,7 @@ class CodeBlockStmtSyntax : public StmtSyntax {
   };
   friend struct SyntaxFactory;
   friend class CodeBlockStmtSyntaxData;
+  friend class FunctionDeclSyntax;
 
   CodeBlockStmtSyntax(const RC<SyntaxData> Root, CodeBlockStmtSyntaxData *Data);
 

include/swift/Syntax/SyntaxFactory.h

@@ -93,6 +93,19 @@ struct SyntaxFactory {
   /// Make an empty list of declaration members.
   static DeclMembersSyntax makeBlankDeclMembers();
 
+  /// Make a function declaration with the specified elements.
+  static FunctionDeclSyntax
+  makeFunctionDecl(TypeAttributesSyntax Attributes,
+                   DeclModifierListSyntax Modifiers,
+                   RC<TokenSyntax> FuncKeyword,
+                   RC<TokenSyntax> Identifier,
+                   llvm::Optional<GenericParameterClauseSyntax> GenericParams,
+                   FunctionSignatureSyntax Signature,
+                   llvm::Optional<CodeBlockStmtSyntax> Body);
+
+  /// Make a function declaration with all missing elements.
+  static FunctionDeclSyntax makeBlankFunctionDecl();
+
 #pragma mark - function-parameter
 
   /// Make a function parameter with the given elements.
@@ -233,6 +246,19 @@ struct SyntaxFactory {
 
 #pragma mark - Tokens
 
+  /// Make a 'static' keyword with the specified leading and trailing trivia.
+  static RC<TokenSyntax> makeStaticKeyword(const Trivia &LeadingTrivia,
+                                           const Trivia &TrailingTrivia);
+
+
+  /// Make a 'public' keyword with the specified leading and trailing trivia.
+  static RC<TokenSyntax> makePublicKeyword(const Trivia &LeadingTrivia,
+                                           const Trivia &TrailingTrivia);
+
+  /// Make a 'func' keyword with the specified leading and trailing trivia.
+  static RC<TokenSyntax> makeFuncKeyword(const Trivia &LeadingTrivia,
+                                         const Trivia &TrailingTrivia);
+
   /// Make a 'fallthrough' keyword with the specified leading and
   /// trailing trivia.
   static RC<TokenSyntax> makeFallthroughKeyword(const Trivia &LeadingTrivia,

include/swift/Syntax/SyntaxKinds.def

@@ -40,8 +40,9 @@ ABSTRACT_SYNTAX(DeclSyntax, Syntax)
   SYNTAX(UnknownDecl, DeclSyntax)
   SYNTAX(StructDecl, DeclSyntax)
   SYNTAX(TypeAliasDecl, DeclSyntax)
+  SYNTAX(FunctionDecl, DeclSyntax)
 
-SYNTAX_RANGE(Decl, MissingDecl, TypeAliasDecl)
+SYNTAX_RANGE(Decl, MissingDecl, FunctionDecl)
 
 SYNTAX(DeclMembers, Syntax)
 SYNTAX(GenericParameter, Syntax)

include/swift/Syntax/TypeSyntax.h

@@ -187,6 +187,7 @@ class TypeAttributesSyntax final : public Syntax {
   friend class TypeAttributesSyntaxData;
   friend class SyntaxData;
   friend class FunctionSignatureSyntax;
+  friend class FunctionDeclSyntax;
 
   using DataType = TypeAttributesSyntaxData;
 

lib/Syntax/DeclSyntax.cpp

@@ -12,8 +12,11 @@
 
 #include "swift/Syntax/DeclSyntax.h"
 #include "swift/Syntax/ExprSyntax.h"
+#include "swift/Syntax/GenericSyntax.h"
 #include "swift/Syntax/RawSyntax.h"
+#include "swift/Syntax/StmtSyntax.h"
 #include "swift/Syntax/SyntaxFactory.h"
+#include "swift/Syntax/TypeSyntax.h"
 
 using namespace swift;
 using namespace swift::syntax;
@@ -817,3 +820,206 @@ withReturnTypeSyntax(TypeSyntax NewReturnTypeSyntax) const {
   return Data->replaceChild<FunctionSignatureSyntax>(
     NewReturnTypeSyntax.getRaw(), Cursor::ReturnType);
 }
+
+#pragma mark - function-declaration-data
+
+FunctionDeclSyntaxData::
+FunctionDeclSyntaxData(const RC<RawSyntax> Raw,
+                       const SyntaxData *Parent,
+                       const CursorIndex IndexInParent)
+  : SyntaxData(Raw, Parent, IndexInParent) {
+  assert(Raw->Kind == SyntaxKind::FunctionDecl);
+  assert(Raw->Layout.size() == 8);
+  syntax_assert_child_kind(Raw, FunctionDeclSyntax::Cursor::Attributes,
+                           SyntaxKind::TypeAttributes);
+  syntax_assert_child_kind(Raw, FunctionDeclSyntax::Cursor::Modifiers,
+                           SyntaxKind::DeclModifierList);
+  syntax_assert_child_token_text(Raw, FunctionDeclSyntax::Cursor::FuncKeyword,
+                                 tok::kw_func, "func");
+  syntax_assert_child_token(Raw, FunctionDeclSyntax::Cursor::Identifier,
+                            tok::identifier);
+  syntax_assert_child_kind(Raw,
+                           FunctionDeclSyntax::Cursor::GenericParameterClause,
+                           SyntaxKind::GenericParameterClause);
+  syntax_assert_child_kind(Raw, FunctionDeclSyntax::Cursor::Signature,
+                           SyntaxKind::FunctionSignature);
+  syntax_assert_child_kind(Raw, FunctionDeclSyntax::Cursor::GenericWhereClause,
+                           SyntaxKind::GenericWhereClause);
+  syntax_assert_child_kind(Raw, FunctionDeclSyntax::Cursor::Body,
+                           SyntaxKind::CodeBlockStmt);
+}
+
+RC<FunctionDeclSyntaxData> FunctionDeclSyntaxData::make(const RC<RawSyntax> Raw,
+                                       const SyntaxData *Parent,
+                                       const CursorIndex IndexInParent) {
+  return RC<FunctionDeclSyntaxData> {
+    new FunctionDeclSyntaxData {
+      Raw, Parent, IndexInParent
+    }
+  };
+}
+
+RC<FunctionDeclSyntaxData> FunctionDeclSyntaxData::makeBlank() {
+  auto Raw = RawSyntax::make(SyntaxKind::FunctionDecl,
+    {
+      RawSyntax::missing(SyntaxKind::TypeAttributes),
+      RawSyntax::missing(SyntaxKind::DeclModifierList),
+      TokenSyntax::missingToken(tok::kw_func, "func"),
+      TokenSyntax::missingToken(tok::identifier, ""),
+      RawSyntax::missing(SyntaxKind::GenericParameterClause),
+      RawSyntax::missing(SyntaxKind::FunctionSignature),
+      RawSyntax::missing(SyntaxKind::GenericWhereClause),
+      RawSyntax::missing(SyntaxKind::CodeBlockStmt),
+    },
+    SourcePresence::Present);
+  return make(Raw);
+}
+
+#pragma mark - function-declaration-API
+
+TypeAttributesSyntax FunctionDeclSyntax::getAttributes() const {
+  auto RawAttrs = getRaw()->getChild(Cursor::Attributes);
+
+  auto *MyData = getUnsafeData<FunctionDeclSyntax>();
+
+  auto &ChildPtr = *reinterpret_cast<std::atomic<uintptr_t>*>(
+    &MyData->CachedAttributes);
+
+  SyntaxData::realizeSyntaxNode<ExprSyntax>(ChildPtr, RawAttrs, MyData,
+                                            cursorIndex(Cursor::Attributes));
+  
+  return { Root, MyData->CachedAttributes.get() };
+}
+
+FunctionDeclSyntax
+FunctionDeclSyntax::withAttributes(TypeAttributesSyntax NewAttributes) const {
+  return Data->replaceChild<FunctionDeclSyntax>(NewAttributes.getRaw(),
+                                                Cursor::Attributes);
+}
+
+DeclModifierListSyntax FunctionDeclSyntax::getModifiers() const {
+  auto RawModifiers = getRaw()->getChild(Cursor::Attributes);
+
+  auto *MyData = getUnsafeData<FunctionDeclSyntax>();
+
+  auto &ChildPtr = *reinterpret_cast<std::atomic<uintptr_t>*>(
+    &MyData->CachedModifiers);
+
+  SyntaxData::realizeSyntaxNode<DeclModifierListSyntax>(ChildPtr, RawModifiers,
+    MyData, cursorIndex(Cursor::Modifiers));
+  
+  return { Root, MyData->CachedModifiers.get() };
+}
+
+FunctionDeclSyntax
+FunctionDeclSyntax::withModifiers(DeclModifierListSyntax NewModifiers) const {
+  return Data->replaceChild<FunctionDeclSyntax>(NewModifiers.getRaw(),
+                                                Cursor::Modifiers);
+}
+
+RC<TokenSyntax> FunctionDeclSyntax::getFuncKeyword() const {
+  return cast<TokenSyntax>(getRaw()->getChild(Cursor::FuncKeyword));
+}
+
+FunctionDeclSyntax
+FunctionDeclSyntax::withFuncKeyword(RC<TokenSyntax> NewFuncKeyword) const {
+  syntax_assert_token_is(NewFuncKeyword, tok::kw_func, "func");
+  return Data->replaceChild<FunctionDeclSyntax>(NewFuncKeyword,
+                                                Cursor::FuncKeyword);
+
+}
+
+RC<TokenSyntax> FunctionDeclSyntax::getIdentifier() const {
+  return cast<TokenSyntax>(getRaw()->getChild(Cursor::Identifier));
+}
+
+FunctionDeclSyntax
+FunctionDeclSyntax::withIdentifier(RC<TokenSyntax> NewIdentifier) const {
+  assert(NewIdentifier->getTokenKind() == tok::identifier);
+  return Data->replaceChild<FunctionDeclSyntax>(NewIdentifier,
+                                                Cursor::Identifier);
+}
+
+llvm::Optional<GenericParameterClauseSyntax>
+FunctionDeclSyntax::getGenericParameterClause() const {
+  auto RawGenericParams = getRaw()->getChild(Cursor::Attributes);
+  if (RawGenericParams->isMissing()) {
+    return llvm::None;
+  }
+
+  auto *MyData = getUnsafeData<FunctionDeclSyntax>();
+
+  auto &ChildPtr = *reinterpret_cast<std::atomic<uintptr_t>*>(
+    &MyData->CachedGenericParams);
+
+  SyntaxData::realizeSyntaxNode<DeclModifierListSyntax>(ChildPtr,
+    RawGenericParams, MyData, cursorIndex(Cursor::GenericParameterClause));
+
+  GenericParameterClauseSyntax Params {
+    Root,
+    MyData->CachedGenericParams.get()
+  };
+  
+  return Params;
+}
+
+FunctionDeclSyntax FunctionDeclSyntax::withGenericParameterClause(
+    llvm::Optional<GenericParameterClauseSyntax> NewGenericParams) const {
+  auto RawParams = NewGenericParams.hasValue()
+    ? NewGenericParams->getRaw()
+    : SyntaxFactory::makeBlankGenericParameterClause().getRaw();
+  return Data->replaceChild<FunctionDeclSyntax>(RawParams,
+                                                Cursor::GenericParameterClause);
+
+}
+
+FunctionSignatureSyntax FunctionDeclSyntax::getSignature() const {
+  auto RawSig = getRaw()->getChild(Cursor::Attributes);
+
+  auto *MyData = getUnsafeData<FunctionDeclSyntax>();
+
+  auto &ChildPtr = *reinterpret_cast<std::atomic<uintptr_t>*>(
+    &MyData->CachedSignature);
+
+  SyntaxData::realizeSyntaxNode<FunctionSignatureSyntax>(ChildPtr, RawSig,
+    MyData, cursorIndex(Cursor::Signature));
+
+  return { Root, MyData->CachedSignature.get() };
+}
+
+FunctionDeclSyntax
+FunctionDeclSyntax::withSignature(FunctionSignatureSyntax NewSignature) const {
+  return Data->replaceChild<FunctionDeclSyntax>(NewSignature.getRaw(),
+                                                Cursor::Signature);
+}
+
+llvm::Optional<CodeBlockStmtSyntax> FunctionDeclSyntax::getBody() const {
+  auto RawBody = getRaw()->getChild(Cursor::Body);
+  if (RawBody->isMissing()) {
+    return llvm::None;
+  }
+
+  auto *MyData = getUnsafeData<FunctionDeclSyntax>();
+
+  auto &ChildPtr = *reinterpret_cast<std::atomic<uintptr_t>*>(
+    &MyData->CachedBody);
+
+  SyntaxData::realizeSyntaxNode<CodeBlockStmtSyntax>(ChildPtr,
+    RawBody, MyData, cursorIndex(Cursor::Body));
+  
+  CodeBlockStmtSyntax Body {
+    Root,
+    MyData->CachedBody.get()
+  };
+  
+  return Body;
+}
+
+FunctionDeclSyntax FunctionDeclSyntax::
+withBody(llvm::Optional<CodeBlockStmtSyntax> NewBody) const {
+  auto RawBody = NewBody.hasValue()
+    ? NewBody->getRaw()
+    : SyntaxFactory::makeBlankCodeBlock().getRaw();
+  return Data->replaceChild<FunctionDeclSyntax>(RawBody,
+                                                Cursor::Body);
+}

lib/Syntax/GenericSyntax.cpp

@@ -149,9 +149,9 @@ GenericParameterClauseSyntaxData(RC<RawSyntax> Raw,
 }
 
 RC<GenericParameterClauseSyntaxData>
-GenericParameterClauseSyntaxData::make(RC<RawSyntax> Raw,
+GenericParameterClauseSyntaxData::make(const RC<RawSyntax> Raw,
                                        const SyntaxData *Parent,
-                                       CursorIndex IndexInParent) {
+                                       const CursorIndex IndexInParent) {
   return RC<GenericParameterClauseSyntaxData> {
     new GenericParameterClauseSyntaxData {
       Raw, Parent, IndexInParent,
@@ -173,7 +173,7 @@ GenericParameterClauseSyntaxData::makeBlank() {
 #pragma mark - generic-parameter-clause API
 
 GenericParameterClauseSyntax::
-GenericParameterClauseSyntax(RC<SyntaxData> Root,
+GenericParameterClauseSyntax(const RC<SyntaxData> Root,
                              const GenericParameterClauseSyntaxData *Data)
   : Syntax(Root, Data) {}
 

lib/Syntax/SyntaxFactory.cpp

@@ -455,6 +455,30 @@ FunctionCallExprSyntax SyntaxFactory::makeBlankFunctionCallExpr() {
 
 #pragma mark - Tokens
 
+RC<TokenSyntax>
+SyntaxFactory::makeStaticKeyword(const Trivia &LeadingTrivia,
+                                 const Trivia &TrailingTrivia) {
+  return TokenSyntax::make(tok::kw_static, "static",
+                           SourcePresence::Present,
+                           LeadingTrivia, TrailingTrivia);
+}
+
+RC<TokenSyntax>
+SyntaxFactory::makePublicKeyword(const Trivia &LeadingTrivia,
+                                 const Trivia &TrailingTrivia) {
+  return TokenSyntax::make(tok::kw_public, "public",
+                           SourcePresence::Present,
+                           LeadingTrivia, TrailingTrivia);
+}
+
+RC<TokenSyntax>
+SyntaxFactory::makeFuncKeyword(const Trivia &LeadingTrivia,
+                                      const Trivia &TrailingTrivia) {
+  return TokenSyntax::make(tok::kw_func, "func",
+                           SourcePresence::Present,
+                           LeadingTrivia, TrailingTrivia);
+}
+
 RC<TokenSyntax>
 SyntaxFactory::makeFallthroughKeyword(const Trivia &LeadingTrivia,
                                       const Trivia &TrailingTrivia) {

unittests/Syntax/DeclSyntaxTests.cpp

@@ -1,6 +1,7 @@
 #include "swift/Syntax/SyntaxFactory.h"
 #include "swift/Syntax/DeclSyntax.h"
 #include "swift/Syntax/ExprSyntax.h"
+#include "swift/Syntax/StmtSyntax.h"
 #include "llvm/ADT/SmallString.h"
 #include "gtest/gtest.h"
 
@@ -465,5 +466,109 @@ TEST(DeclSyntaxTests, FunctionSignatureWithAPIs) {
 
 #pragma mark - function-declaration
 
-// TODO: Nodes
-// TODO: Tests
+DeclModifierListSyntax getCannedModifiers() {
+  auto PublicID = SyntaxFactory::makePublicKeyword({}, Trivia::spaces(1));
+  auto NoLParen = TokenSyntax::missingToken(tok::l_paren, "(");
+  auto NoArgument = TokenSyntax::missingToken(tok::identifier, "");
+  auto NoRParen = TokenSyntax::missingToken(tok::r_paren, ")");
+  auto Public = SyntaxFactory::makeDeclModifier(PublicID, NoLParen, NoArgument,
+                                                NoRParen);
+
+  auto StaticKW = SyntaxFactory::makeStaticKeyword({}, Trivia::spaces(1));
+  auto Static = SyntaxFactory::makeDeclModifier(StaticKW, NoLParen, NoArgument,
+                                                NoRParen);
+
+  return SyntaxFactory::makeBlankDeclModifierList()
+    .appending(Public)
+    .appending(Static)
+    .castTo<DeclModifierListSyntax>();
+}
+
+GenericParameterClauseSyntax getCannedGenericParams() {
+  GenericParameterClauseBuilder GB;
+
+  auto LAngle = SyntaxFactory::makeLeftAngleToken({}, {});
+  auto RAngle = SyntaxFactory::makeLeftAngleToken({}, Trivia::spaces(1));
+
+  auto T = SyntaxFactory::makeGenericParameter("T", {}, {});
+  auto U = SyntaxFactory::makeGenericParameter("U", {}, {});
+
+  auto Comma = SyntaxFactory::makeCommaToken({}, Trivia::spaces(1));
+
+  GB.addParameter(llvm::None, T);
+  GB.addParameter(Comma, U);
+  GB.useLeftAngleBracket(LAngle);
+  GB.useLeftAngleBracket(RAngle);
+
+  return GB.build();
+}
+
+CodeBlockStmtSyntax getCannedBody() {
+  auto NoSign = TokenSyntax::missingToken(tok::oper_prefix, "-");
+  auto OneDigits = SyntaxFactory::makeIntegerLiteralToken("1", {}, {});
+  auto One = SyntaxFactory::makeIntegerLiteralExpr(NoSign, OneDigits);
+  auto ReturnKW =
+    SyntaxFactory::makeReturnKeyword(Trivia::newlines(1) + Trivia::spaces(1),
+                                     {});
+  auto Return = SyntaxFactory::makeReturnStmt(ReturnKW, One);
+
+  auto Stmts = SyntaxFactory::makeBlankStmtList()
+    .appending(Return)
+    .castTo<StmtListSyntax>();
+
+  auto LBrace = SyntaxFactory::makeLeftBrace({}, {});
+  auto RBrace = SyntaxFactory::makeRightBrace(Trivia::newlines(1), {});
+
+  return SyntaxFactory::makeCodeBlock(LBrace, Stmts, RBrace);
+}
+
+FunctionDeclSyntax getCannedFunctionDecl() {
+  auto NoAttributes = SyntaxFactory::makeBlankTypeAttributes();
+  auto Foo = SyntaxFactory::makeIdentifier("foo", {}, {});
+  auto FuncKW = SyntaxFactory::makeFuncKeyword({}, Trivia::spaces(1));
+  auto Modifiers = getCannedModifiers();
+  auto GenericParams = getCannedGenericParams();
+  auto Signature = getCannedFunctionSignature();
+  auto Body = getCannedBody();
+
+  return SyntaxFactory::makeFunctionDecl(NoAttributes, Modifiers, FuncKW, Foo,
+                                         GenericParams, Signature, Body);
+}
+
+TEST(DeclSyntaxTests, FunctionDeclMakeAPIs) {
+  {
+    SmallString<1> Scratch;
+    llvm::raw_svector_ostream OS(Scratch);
+    SyntaxFactory::makeBlankFunctionDecl().print(OS);
+    ASSERT_EQ(OS.str().str(), "");
+  }
+  {
+    SmallString<64> Scratch;
+    llvm::raw_svector_ostream OS(Scratch);
+    getCannedFunctionDecl().print(OS);
+    ASSERT_EQ(OS.str().str(),
+              "public static func foo(x: Int, y: Int) throws -> Int {\n"
+              "  return 1\n"
+              "}");
+  }
+}
+
+TEST(DeclSyntaxTests, FunctionDeclGetAPIs) {
+  {
+    SmallString<1> Scratch;
+    llvm::raw_svector_ostream OS(Scratch);
+    SyntaxFactory::makeBlankFunctionDecl().print(OS);
+    ASSERT_EQ(OS.str().str(), "");
+  }
+  {
+
+  }
+}
+
+TEST(DeclSyntaxTests, FunctionDeclWithAPIs) {
+
+}
+
+TEST(DeclSyntaxTests, FunctionDeclBuilderAPIs) {
+
+}