Anonymous records!

lib/fcs/FSharp.Compiler.Service.xml

@@ -28180,7 +28180,7 @@ Special cases where representation uses Lambda.
 </member>
 <member name="T:Microsoft.FSharp.Compiler.SourceCodeServices.FSharpObjectExprOverride">
 <summary>
- Represents a checked method in an object expression, as seen by the F# language.  
+ Represents a checked method in an object expression, as seen by the F# language.
 </summary>
 </member>
 <member name="P:Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr.Type">
@@ -28195,12 +28195,12 @@ Special cases where representation uses Lambda.
 </member>
 <member name="P:Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr.ImmediateSubExpressions">
 <summary>
- The immediate sub-expressions of the expression.  
+ The immediate sub-expressions of the expression.
 </summary>
 </member>
 <member name="T:Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr">
 <summary>
- Represents a checked and reduced expression, as seen by the F# language.  The active patterns 
+ Represents a checked and reduced expression, as seen by the F# language.  The active patterns
  in &apos;FSharp.Compiler.SourceCodeServices&apos; can be used to analyze information about the expression.
 
  Pattern matching is reduced to decision trees and conditional tests. Some other
@@ -29777,7 +29777,7 @@ Special cases where representation uses Lambda.
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|TraitCall|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
 <summary>
- Matches expressions for an unresolved call to a trait 
+ Matches expressions for an unresolved call to a trait
 </summary>
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|ObjectExpr|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
@@ -29817,7 +29817,7 @@ Special cases where representation uses Lambda.
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|WhileLoop|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
 <summary>
- Matches while loops 
+ Matches while loops
 </summary>
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|FastIntegerForLoop|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
@@ -29827,7 +29827,7 @@ Special cases where representation uses Lambda.
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|Sequential|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
 <summary>
- Matches sequential expressions 
+ Matches sequential expressions
 </summary>
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|AddressOf|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
@@ -29863,7 +29863,7 @@ Special cases where representation uses Lambda.
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|NewArray|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
 <summary>
- Matches array expressions 
+ Matches array expressions
 </summary>
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|Coerce|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
@@ -29878,7 +29878,7 @@ Special cases where representation uses Lambda.
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|NewTuple|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
 <summary>
- Matches tuple expressions 
+ Matches tuple expressions
 </summary>
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|UnionCaseTest|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
@@ -29916,9 +29916,20 @@ Special cases where representation uses Lambda.
  Matches expressions which get a field from a record or class
 </summary>
 </member>
+<member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|AnonRecordGet|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
+<summary>
+ Matches expressions getting a field from an anonymous record. The integer represents the
+ index into the sorted fields of the anonymous record.
+</summary>
+</member>
+<member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|NewAnonRecord|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
+<summary>
+ Matches anonymous record expressions
+</summary>
+</member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|NewRecord|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
 <summary>
- Matches record expressions 
+ Matches record expressions
 </summary>
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|LetRec|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
@@ -29943,7 +29954,7 @@ Special cases where representation uses Lambda.
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|NewObject|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
 <summary>
- Matches expressions which are calls to object constructors 
+ Matches expressions which are calls to object constructors
 </summary>
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|Call|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
@@ -29985,12 +29996,12 @@ Special cases where representation uses Lambda.
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|Application|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
 <summary>
- Matches expressions which are the application of function values 
+ Matches expressions which are the application of function values
 </summary>
 </member>
 <member name="M:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns.|Value|_|(Microsoft.FSharp.Compiler.SourceCodeServices.FSharpExpr)">
 <summary>
- Matches expressions which are uses of values 
+ Matches expressions which are uses of values
 </summary>
 </member>
 <member name="T:Microsoft.FSharp.Compiler.SourceCodeServices.BasicPatterns">

src/Fable.Transforms/AST/AST.Fable.fs

@@ -131,6 +131,7 @@ type ImportKind =
 
 type EnumKind = NumberEnum of Expr | StringEnum of Expr
 type NewArrayKind = ArrayValues of Expr list | ArrayAlloc of Expr
+type NewRecordKind = DeclaredRecord of FSharpEntity | AnonymousRecord of fieldNames: string[]
 
 type ValueKind =
     | TypeInfo of Type * SourceLocation option // Error messages need location info
@@ -146,7 +147,7 @@ type ValueKind =
     | NewArray of NewArrayKind * Type
     | NewList of headAndTail: (Expr * Expr) option * Type
     | NewTuple of Expr list
-    | NewRecord of Expr list * FSharpEntity * genArgs: Type list
+    | NewRecord of Expr list * NewRecordKind * genArgs: Type list
     | NewUnion of Expr list * FSharpUnionCase * FSharpEntity * genArgs: Type list
     | NewErasedUnion of Expr * genericArgs: Type list
     member this.Type =
@@ -169,7 +170,10 @@ type ValueKind =
         | NewArray(_, t) -> Array t
         | NewList(_, t) -> List t
         | NewTuple exprs -> exprs |> List.map (fun e -> e.Type) |> Tuple
-        | NewRecord(_, ent, genArgs) -> DeclaredType(ent, genArgs)
+        | NewRecord(_, kind, genArgs) ->
+            match kind with
+            | DeclaredRecord ent -> DeclaredType(ent, genArgs)
+            | AnonymousRecord _ -> Any
         | NewUnion(_, _, ent, genArgs) -> DeclaredType(ent, genArgs)
         | NewErasedUnion(_, genArgs) -> ErasedUnion genArgs
 

src/Fable.Transforms/FSharp2Fable.fs

@@ -533,6 +533,13 @@ let private transformExpr (com: IFableCompiler) (ctx: Context) fsExpr =
         | _ -> return failwith "makeFunctionArgs returns args with different length"
 
     // Getters and Setters
+    | BasicPatterns.AnonRecordGet(callee, calleeType, fieldIndex) ->
+        let! callee = transformExpr com ctx callee
+        let fieldName = calleeType.AnonRecordTypeDetails.SortedFieldNames.[fieldIndex]
+        let typ = makeType com ctx.GenericArgs fsExpr.Type
+        let kind = Fable.FieldGet(fieldName, false, typ)
+        return Fable.Get(callee, kind, typ, makeRangeFrom fsExpr)
+
     | BasicPatterns.FSharpFieldGet(callee, calleeType, field) ->
         let! callee = transformExprOpt com ctx callee
         let callee =
@@ -637,7 +644,11 @@ let private transformExpr (com: IFableCompiler) (ctx: Context) fsExpr =
     | BasicPatterns.NewRecord(fsType, argExprs) ->
         let! argExprs = transformExprList com ctx argExprs
         let genArgs = makeGenArgs com ctx.GenericArgs (getGenericArguments fsType)
-        return Fable.NewRecord(argExprs, fsType.TypeDefinition, genArgs) |> Fable.Value
+        return Fable.NewRecord(argExprs, Fable.DeclaredRecord fsType.TypeDefinition, genArgs) |> Fable.Value
+
+    | BasicPatterns.NewAnonRecord(fsType, argExprs) ->
+        let! argExprs = transformExprList com ctx argExprs
+        return Fable.NewRecord(argExprs, Fable.AnonymousRecord fsType.AnonRecordTypeDetails.SortedFieldNames, []) |> Fable.Value
 
     | BasicPatterns.NewUnionCase(fsType, unionCase, argExprs) ->
         let! argExprs = transformExprList com ctx argExprs

src/Fable.Transforms/Fable2Babel.fs

@@ -213,9 +213,10 @@ module Util =
         |> ArrayExpression :> Expression
 
     let makeJsObject pairs =
-        pairs |> List.mapToArray (fun (name, value) ->
+        pairs |> Seq.map (fun (name, value) ->
             let prop, computed = memberFromName name
             ObjectProperty(prop, value, computed_=computed) |> U3.Case1)
+        |> Seq.toArray
         |> ObjectExpression :> Expression
 
     let assign range left right =
@@ -552,10 +553,17 @@ module Util =
             match kind with
             | Fable.NumberEnum x
             | Fable.StringEnum x -> com.TransformAsExpr(ctx, x)
-        | Fable.NewRecord(values, ent, _) ->
-            let consRef = jsConstructor com ctx ent
+        | Fable.NewRecord(values, kind, _) ->
             let values = List.mapToArray (fun x -> com.TransformAsExpr(ctx, x)) values
-            upcast NewExpression(consRef, values)
+            match kind with
+            | Fable.DeclaredRecord ent ->
+                let consRef = jsConstructor com ctx ent
+                upcast NewExpression(consRef, values)
+            | Fable.AnonymousRecord fieldNames ->
+                Array.zip fieldNames values
+                |> makeJsObject
+                |> Array.singleton
+                |> coreLibCall com ctx "Types" "anonRecord"
         | Fable.NewUnion(values, uci, ent, _) ->
             // Union cases with EraseAttribute are used for `Custom`-like cases in unions meant for `keyValueList`
             match FSharp2Fable.Helpers.tryFindAtt Atts.erase uci.Attributes with

src/Fable.Transforms/FableTransforms.fs

@@ -460,9 +460,12 @@ module private Transforms =
             let info = { info with Args = uncurryArgs com info.SignatureArgTypes info.Args }
             Operation(Emit(macro, Some info), t, r)
         // Uncurry also values in setters or new record/union/tuple
-        | Value(NewRecord(args, ent, genArgs)) ->
-            let args = uncurryConsArgs args ent.FSharpFields
-            Value(NewRecord(args, ent, genArgs))
+        | Value(NewRecord(args, kind, genArgs)) ->
+            let args =
+                match kind with
+                | DeclaredRecord ent -> uncurryConsArgs args ent.FSharpFields
+                | AnonymousRecord _ -> uncurryArgs com AutoUncurrying args
+            Value(NewRecord(args, kind, genArgs))
         | Value(NewUnion(args, uci, ent, genArgs)) ->
             let args = uncurryConsArgs args uci.UnionCaseFields
             Value(NewUnion(args, uci, ent, genArgs))

src/fable-library/Types.js

@@ -215,6 +215,10 @@ Record.prototype.CompareTo = function(other) {
   return recordCompare(this, other);
 };
 
+export function anonRecord(o) {
+  return Object.assign(Object.create(Record), o);
+}
+
 export const FSharpRef = declare(function FSharpRef(contents) {
   this.contents = contents;
 }, Record);