Parse a generic parameter list within a function declaration, and

introduce the generic type parameters (which are simply type aliases
for a to-be-determined archetype type) into scope for name
lookup. We can now parse something like

  func f<T, U : Range>(x : T, y : U) { }

but there is no semantic analysis or even basic safety checking (yet).




Swift SVN r2197

include/swift/AST/Decl.h

@@ -47,6 +47,7 @@ namespace swift {
   class Stmt;
   class StructType;
   class TupleType;
+  class ValueDecl;
   
 enum class DeclKind {
 #define DECL(Id, Parent) Id,
@@ -142,6 +143,32 @@ public:
   }
 };
 
+/// GenericParam - A parameter to a generic function or type, as declared in
+/// the list of generic parameters, e.g., the T and U in:
+///
+/// \code
+/// func f<T : Range, U>(t : T, u : U) { /* ... */ }
+/// \endcode
+class GenericParam {
+  TypeAliasDecl *TypeParam;
+
+public:
+  /// Construct a generic parameter from a type parameter.
+  GenericParam(TypeAliasDecl *TypeParam) : TypeParam(TypeParam) { }
+
+  /// getDecl - Retrieve the generic parameter declaration.
+  ValueDecl *getDecl() const {
+    return reinterpret_cast<ValueDecl *>(TypeParam);
+  }
+
+  /// getAsTypeParam - Retrieve the generic parameter as a type parameter.
+  TypeAliasDecl *getAsTypeParam() const { return TypeParam; }
+
+  /// setDeclContext - Set the declaration context for the generic parameter,
+  /// once it is known.
+  void setDeclContext(DeclContext *DC);
+};
+
 /// ImportDecl - This represents a single import declaration, e.g.:
 ///   import swift
 ///   import swift.int
@@ -948,6 +975,9 @@ public:
   static bool classof(const ConstructorDecl *D) { return true; }
 };
 
+inline void GenericParam::setDeclContext(DeclContext *DC) {
+  TypeParam->setDeclContext(DC);
+}
 
 } // end namespace swift
 

include/swift/AST/Diagnostics.def

@@ -538,6 +538,17 @@ ERROR(asmname_expected_string_literal,attribute_parsing,none,
 ERROR(asmname_interpolated_string,attribute_parsing,none,
       "asmname cannot be an interpolated string literal", ())
       
+//------------------------------------------------------------------------------
+// Generics parsing diagnostics
+//------------------------------------------------------------------------------
+ERROR(expected_rangle_generics_param,parsing,none,
+      "expected '>' to complete generic parameter list", ())
+ERROR(expected_generics_parameter_name,parsing,none,
+      "expected an identifier to name generic parameter", ())
+ERROR(expected_generics_type_restriction,parsing,none,
+      "expected a type name or protocol composition restricting %0",
+      (Identifier))
+
 //==============================================================================
 // Semantic Analysis Diagnostics
 //==============================================================================

include/swift/Basic/Optional.h

@@ -107,7 +107,15 @@ namespace swift {
     }
     
     ~Optional() { reset(); }
-    
+
+    // Create a new object by constructing it in place with the given arguments.
+    template<typename ...ArgTypes>
+    void emplace(ArgTypes &&...Args) {
+      reset();
+      HasValue = true;
+      new (getPointer()) T(std::forward<ArgTypes>(Args)...);
+    }
+
     void reset() {
       if (!HasValue)
         return;

lib/Parse/CMakeLists.txt

@@ -4,6 +4,7 @@ add_swift_library(swiftParse
   Parser.h
   ParseDecl.cpp
   ParseExpr.cpp
+  ParseGeneric.cpp
   ParsePattern.cpp
   ParseStmt.cpp
   ParseType.cpp

lib/Parse/ParseDecl.cpp

@@ -1107,8 +1107,8 @@ Pattern *Parser::buildImplicitThisParameter() {
 /// is true, we parse both productions.
 ///
 ///   decl-func:
-///     'static'? 'func' attribute-list any-identifier func-signature 
-///               stmt-brace?
+///     'static'? 'func' attribute-list any-identifier generic-params?
+///               func-signature stmt-brace?
 ///
 /// NOTE: The caller of this method must ensure that the token sequence is
 /// either 'func' or 'static' 'func'.
@@ -1136,6 +1136,26 @@ FuncDecl *Parser::parseDeclFunc(bool hasContainerType) {
   if (parseAnyIdentifier(Name, diag::expected_identifier_in_decl, "func"))
     return 0;
 
+  // Placeholder that may hold a new scope containing the generic parameters,
+  // if there are any.
+  Optional<Scope> GenericsScope(this, /*AllowLookup=*/true);
+
+  // Parse the generic-params, if present.
+  SmallVector<GenericParam, 4> GenericParams;
+  if (startsWithLess(Tok)) {
+    parseGenericParameters(GenericParams);
+
+    // If there were any generic parameters, introduce the new scope to
+    // hold those generic parameters.
+    if (!GenericParams.empty()) {
+      GenericsScope.emplace(this, /*AllowLookup=*/true);
+      
+      for (auto Param : GenericParams) {
+        ScopeInfo.addToScope(Param.getDecl());
+      }
+    }
+  }
+
   // We force first type of a func declaration to be a tuple for consistency.
   if (Tok.isNotAnyLParen()) {
     diagnose(Tok, diag::func_decl_without_paren);
@@ -1143,7 +1163,7 @@ FuncDecl *Parser::parseDeclFunc(bool hasContainerType) {
   }
 
   SmallVector<Pattern*, 8> Params;
-
+  
   // If we're within a container and this isn't a static method, add an
   // implicit first pattern to match the container type as an element
   // named 'this'.  This turns "(int)->int" on FooTy into "(this :
@@ -1163,9 +1183,15 @@ FuncDecl *Parser::parseDeclFunc(bool hasContainerType) {
   FuncExpr *FE = 0;
   {
     Scope FnBodyScope(this, /*AllowLookup=*/true);
-
+    
     FE = actOnFuncExprStart(FuncLoc, FuncTy, Params);
 
+    // Now that we have a context, update the generic parameters with that
+    // context.
+    for (auto Param : GenericParams) {
+      Param.setDeclContext(FE);
+    }
+
     // Establish the new context.
     ContextChange CC(*this, FE);
     
@@ -1179,10 +1205,10 @@ FuncDecl *Parser::parseDeclFunc(bool hasContainerType) {
         FE = 0; // FIXME: Should do some sort of error recovery here.
       } else {
         FE->setBody(Body.get());
-
+        
         auto& Captures = ValCaptures.back();
         ValueDecl** CaptureCopy =
-            Context.AllocateCopy<ValueDecl*>(Captures.begin(), Captures.end());
+        Context.AllocateCopy<ValueDecl*>(Captures.begin(), Captures.end());
         FE->setCaptures(llvm::makeArrayRef(CaptureCopy, Captures.size()));
       }
       
@@ -1192,7 +1218,10 @@ FuncDecl *Parser::parseDeclFunc(bool hasContainerType) {
       FE = 0;
     }
   }
-  
+
+  // Exit the scope introduced for the generic parameters, if we're in one.
+  GenericsScope.reset();
+
   // Create the decl for the func and add it to the parent scope.
   FuncDecl *FD = new (Context) FuncDecl(StaticLoc, FuncLoc, Name, NameLoc,
                                         FuncTy, FE, CurDeclContext);

lib/Parse/ParseGeneric.cpp

@@ -0,0 +1,104 @@
+//===--- ParseGeneric.cpp - Swift Language Parser for Generics ------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See http://swift.org/LICENSE.txt for license information
+// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// Generic Parsing and AST Building
+//
+//===----------------------------------------------------------------------===//
+#include "Parser.h"
+#include "swift/AST/Diagnostics.h"
+#include "swift/Parse/Lexer.h"
+using namespace swift;
+
+/// parseGenericParameters - Parse a sequence of generic parameters, e.g.,
+/// < T : Comparable, U : Container>
+///
+///   generic-params:
+///     '<' generic-param (',' generic-param)? '>'
+///
+///   generic-param:
+///     identifier
+///     identifier ':' type-identifier
+///     identifier ':' type-composition
+bool
+Parser::parseGenericParameters(SmallVectorImpl<GenericParam> &GenericParams) {
+  // Parse the opening '<'.
+  assert(startsWithLess(Tok) && "Generic parameter list must start with '<'");
+  SourceLoc LAngleLoc = consumeStartingLess();
+
+  // Parse the generic parameter list.
+  bool Invalid = false;
+  while (true) {
+    // Parse the name of the parameter.
+    Identifier Name;
+    SourceLoc NameLoc = Tok.getLoc();
+    if (parseIdentifier(Name, diag::expected_generics_parameter_name)) {
+      Invalid = true;
+      break;
+    }
+
+    // Parse the ':' followed by a type.
+    SmallVector<Type, 1> Inherited;
+    if (Tok.is(tok::colon)) {
+      (void)consumeToken();
+      Type Ty;
+      TypeLoc *TyLoc = nullptr;
+      if (Tok.getKind() == tok::identifier) {
+        parseTypeIdentifier(Ty, TyLoc);
+      } else if (Tok.getKind() == tok::kw_protocol) {
+        parseTypeComposition(Ty, TyLoc);
+      } else {
+        diagnose(Tok.getLoc(), diag::expected_generics_type_restriction, Name);
+        Invalid = true;
+      }
+
+      if (Ty)
+        Inherited.push_back(Ty);
+    }
+
+    // FIXME: Bad location info here
+    TypeAliasDecl *Param
+      = new (Context) TypeAliasDecl(NameLoc, Name, NameLoc, Type(),
+                                    CurDeclContext,
+                                    Context.AllocateCopy(Inherited));
+    GenericParams.push_back(Param);
+    
+    // Parse the comma, if the list continues.
+    if (Tok.is(tok::comma)) {
+      consumeToken();
+      continue;
+    }
+
+    break;
+  }
+
+  // Parse the closing '>'.
+  SourceLoc RAngleLoc;
+  if (!startsWithGreater(Tok)) {
+    if (!Invalid) {
+      diagnose(Tok.getLoc(), diag::expected_rangle_generics_param);
+      diagnose(LAngleLoc, diag::opening_angle);
+      
+      Invalid = true;
+    }
+    
+    // Skip until we hit the '>'.
+    skipUntilAnyOperator();
+    if (startsWithGreater(Tok))
+      RAngleLoc = consumeStartingGreater();
+    else
+      RAngleLoc = Tok.getLoc();
+  } else {
+    RAngleLoc = consumeStartingGreater();
+  }
+
+  return Invalid;
+}

lib/Parse/ParseType.cpp

@@ -247,8 +247,7 @@ bool Parser::parseTypeComposition(Type &Result, TypeLoc *&ResultLoc) {
     // Skip until we hit the '>'.
     skipUntilAnyOperator();
     if (startsWithGreater(Tok))
-      EndLoc = consumeStartingGreater();
-    
+      EndLoc = consumeStartingGreater();    
   } else {
     EndLoc = consumeStartingGreater();
   }

lib/Parse/Parser.h

@@ -327,6 +327,10 @@ public:
   NullablePtr<Stmt> parseStmtFor();
   NullablePtr<Stmt> parseStmtForCStyle(SourceLoc ForLoc);
   NullablePtr<Stmt> parseStmtForEach(SourceLoc ForLoc);
+
+  //===--------------------------------------------------------------------===//
+  // Generics Parsing
+  bool parseGenericParameters(SmallVectorImpl<GenericParam> &GenericParams);
 };
 
 } // end namespace swift

test/Generics/function_decls.swift

@@ -0,0 +1,11 @@
+// RUN: %swift %s -verify
+
+//===----------------------------------------------------------------------===//
+// Generic function declarations
+//===----------------------------------------------------------------------===//
+
+func f0<T>(x : Int, y : Int) { }
+func f1<T : Any>(x : Int, y : Int) { }
+func f2<T : protocol<Range,Any>>(x : Int, y : Int) { }
+func f3<T : () -> ()>(x : Int, y : Int) { } // expected-error{{expected a type name or protocol composition restricting 'T'}}
+func f4<T>(x : T, y : T) { }