Merge: Infer more attribute types

Extend the detection of the static type of attributes from their literal values to support three new cases:

* Simple arrays like `[0, 1, 2]` and `[new Set[Int], new Set[Int]]`. However, it does not accept arrays with an explicit type because we can't subtype/anchor at that point, as far as I know.

* Negative integers and floats. This cheats a bit as the return type of the unary - is defined in the core libary. However this should help 99.9% of the time, in particular for Nit beginners, and a workaround is to declare the attribute static type when defining a different kernel library.

* The `once` keyword.

~~~
class A
       # Now detected
       var i = -1
       var f = -1.0
       var a = [0, 1]
       var o = once [0, 1]

       # These are refused
       var a1 = [0, 1.0, "a"] # Different types
       var a2 = [0, 1: Int] # Can't reliably check subtypes
       var a4 = [1+1] # Expression
       var o1 = once [0, "a"] # Forwarded error
end
~~~

---

You may want to review commit by commit as the first commit is a small refactoring.

Pull-Request: #2614

contrib/nitcc/src/grammar.nit

@@ -897,7 +897,7 @@ class LRState
 	var cname: String is lazy do return name.to_cmangle
 
 	# Number
-	var number: Int = -1
+	var number = -1
 
 	# Set of all items
 	var items = new HashSet[Item]

contrib/objcwrapper/src/objc_model.nit

@@ -45,7 +45,7 @@ class ObjcModel
 	# Objective-C types available in imported modules
 	#
 	# TODO seach in existing wrappers
-	private var imported_types: Array[String] = ["NSObject", "NSString"]
+	private var imported_types = ["NSObject", "NSString"]
 end
 
 # Objective-C class

contrib/opportunity/src/opportunity_model.nit

@@ -127,7 +127,7 @@ class People
 	super DBObject
 
 	# ID in the Database, -1 if not set
-	var id: Int = -1
+	var id = -1
 	# Name of the participant
 	var name: String
 	# Surname of the participant
@@ -270,7 +270,7 @@ class Answer
 	# Name of the answer (title)
 	var name: String
 	# Id in the database, -1 if not set
-	var id: Int = -1
+	var id = -1
 	# Meetup the answer is linked to (null while it is not added in the database or set via API)
 	var meetup: nullable Meetup = null is writable
 

contrib/pep8analysis/src/cfg/cfg_base.nit

@@ -435,7 +435,7 @@ class BasicBlock
 end
 
 private class Counter
-	var count: Int = -1
+	var count = -1
 	fun next : Int
 	do
 		count += 1

contrib/pep8analysis/src/model/model.nit

@@ -65,7 +65,7 @@ class Model
 end
 
 redef class ALine
-	var address: Int = -1
+	var address = -1
 
 	fun size: Int is abstract
 

contrib/sort_downloads/src/sort_downloads.nit

@@ -47,7 +47,7 @@ class Config
 
 	# Super directories with wanted folder names, which will be used to sort
 	# the files (only their name are used, the files won't be copied there).
-	var regex_source_dirs: Array[String] = ["~/Videos/"]
+	var regex_source_dirs = ["~/Videos/"]
 
 	# Will only sort files older than the number of `elapsed_days`.
 	var elapsed_days = 7

contrib/tinks/src/client/client3d.nit

@@ -41,23 +41,23 @@ redef class App
 	# Models
 
 	# Models of rocks
-	var models_rock = new Array[Model].with_items(
+	var models_rock = [
 		new Model("models/Tall_Rock_1_01.obj"),
 		new Model("models/Tall_Rock_2_01.obj"),
 		new Model("models/Tall_Rock_3_01.obj"),
-		new Model("models/Tall_Rock_4_01.obj"))
+		new Model("models/Tall_Rock_4_01.obj")]
 
 	# Models of trees
-	var models_tree = new Array[Model].with_items(
+	var models_tree = [
 		new Model("models/Oak_Dark_01.obj"),
 		new Model("models/Oak_Green_01.obj"),
 		new Model("models/Large_Oak_Dark_01.obj"),
-		new Model("models/Large_Oak_Green_01.obj"))
+		new Model("models/Large_Oak_Green_01.obj")]
 
 	# Models of the debris left by a destroyed tank
-	var models_debris = new Array[Model].with_items(
+	var models_debris = [
 		new Model("models/debris0.obj"),
-		new Model("models/debris1.obj"))
+		new Model("models/debris1.obj")]
 
 	# Model the health pickup
 	var model_health = new Model("models/health.obj")

contrib/tinks/src/game/framework.nit

@@ -31,7 +31,7 @@ class TGame
 	private var clock = new Clock is noserialize
 
 	# Tick count of the last turn (The first turn as a tick of 0)
-	var tick: Int = -1
+	var tick = -1
 
 	# Execute the next turn and return it as a `TTurn`
 	#

lib/actors/examples/chameneos-redux/chameneosredux.nit

@@ -83,8 +83,8 @@ redef class Sys
 	fun blue: Int do return 0
 	fun red: Int do return 1
 	fun yellow: Int do return 2
-	var numbers: Array[String] = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"]
-	var colors: Array[String] = ["blue", "red", "yellow"]
+	var numbers = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"]
+	var colors = ["blue", "red", "yellow"]
 	# Matrix for complementing colors
 	var complements: Array[Array[Int]] = [[0, 2, 1],
 	                                      [2, 1, 0],

lib/bitmap/bitmap.nit

@@ -74,10 +74,10 @@ class Bitmap
 	private var image_size: Int is noinit
 
 	# 14-byte bitmap header
-	private var bitmap_header: Array[Int] = [66, 77, 0, 0, 0, 0, 0, 0, 0, 0, 54, 0, 0, 0]
+	private var bitmap_header = [66, 77, 0, 0, 0, 0, 0, 0, 0, 0, 54, 0, 0, 0]
 
 	# 40-byte dib header
-	private var dib_header: Array[Int] = [40, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	private var dib_header = [40, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 			0, 0, 1, 0, 24, 0, 0, 0, 0, 0,
 			0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
 			0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

lib/bucketed_game.nit

@@ -56,7 +56,7 @@ class Buckets[G: Game]
 	type BUCKET: HashSet[Bucketable[G]]
 
 	private var next_bucket: nullable BUCKET = null
-	private var current_bucket_key: Int = -1
+	private var current_bucket_key = -1
 
 	# Number of `buckets`, default at 100
 	#

lib/curl/curl.nit

@@ -293,7 +293,7 @@ class CurlMail
 	# Protocols supported to send mail to a server
 	#
 	# Default value at `["smtp", "smtps"]`
-	var supported_outgoing_protocol: Array[String] = ["smtp", "smtps"]
+	var supported_outgoing_protocol = ["smtp", "smtps"]
 
 	# Helper method to add pair values to mail content while building it (ex: "To:", "address@mail.com")
 	private fun add_pair_to_content(str: String, att: String, val: nullable String): String

lib/sax/sax_parse_exception.nit

@@ -45,11 +45,11 @@ class SAXParseException
 
 	# The line number of the end of the text that
 	# caused the error or warning, or -1.
-	var line_number: Int = -1
+	var line_number = -1
 
 	# The column number of the end of the text that
 	# caused the error or warning, or -1.
-	var column_number: Int = -1
+	var column_number = -1
 
 	# Create a new SAXParseException from a message and a Locator.
 	#

lib/saxophonit/lexer.nit

@@ -37,7 +37,7 @@ class XophonLexer
 	# Last read byte.
 	#
 	# Equals `-1` on end of file or error.
-	private var last_char: Int = -1
+	private var last_char = -1
 
 	# Before end-of-line handling, was the last read byte a CARRIAGE RETURN?
 	private var was_cr: Bool = false

src/modelize/modelize_property.nit

@@ -1378,66 +1378,7 @@ redef class AAttrPropdef
 		var nexpr = self.n_expr
 		if mtype == null then
 			if nexpr != null then
-				if nexpr isa ANewExpr then
-					mtype = modelbuilder.resolve_mtype_unchecked(mclassdef, nexpr.n_type, true)
-				else if nexpr isa AAsCastExpr then
-					mtype = modelbuilder.resolve_mtype_unchecked(mclassdef, nexpr.n_type, true)
-				else if nexpr isa AIntegerExpr then
-					var cla: nullable MClass = null
-					if nexpr.value isa Int then
-						cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int")
-					else if nexpr.value isa Byte then
-						cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Byte")
-					else if nexpr.value isa Int8 then
-						cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int8")
-					else if nexpr.value isa Int16 then
-						cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int16")
-					else if nexpr.value isa UInt16 then
-						cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "UInt16")
-					else if nexpr.value isa Int32 then
-						cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int32")
-					else if nexpr.value isa UInt32 then
-						cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "UInt32")
-					else
-						# Should not happen, and should be updated as new types are added
-						abort
-					end
-					if cla != null then mtype = cla.mclass_type
-				else if nexpr isa AFloatExpr then
-					var cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Float")
-					if cla != null then mtype = cla.mclass_type
-				else if nexpr isa ACharExpr then
-					var cla: nullable MClass
-					if nexpr.is_ascii then
-						cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Byte")
-					else if nexpr.is_code_point then
-						cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int")
-					else
-						cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Char")
-					end
-					if cla != null then mtype = cla.mclass_type
-				else if nexpr isa ABoolExpr then
-					var cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Bool")
-					if cla != null then mtype = cla.mclass_type
-				else if nexpr isa ASuperstringExpr then
-					var cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "String")
-					if cla != null then mtype = cla.mclass_type
-				else if nexpr isa AStringFormExpr then
-					var cla: nullable MClass
-					if nexpr.is_bytestring then
-						cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Bytes")
-					else if nexpr.is_re then
-						cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Regex")
-					else if nexpr.is_string then
-						cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "String")
-					else
-						abort
-					end
-					if cla != null then mtype = cla.mclass_type
-				else
-					modelbuilder.error(self, "Error: untyped attribute `{mreadpropdef}`. Implicit typing allowed only for literals and new.")
-				end
-
+				mtype = infer_static_type(modelbuilder, nexpr, mclassdef, mmodule, mreadpropdef)
 				if mtype == null then return
 			end
 		else if ntype != null and inherited_type == mtype then
@@ -1485,6 +1426,104 @@ redef class AAttrPropdef
 		check_repeated_types(modelbuilder)
 	end
 
+	# Detect the static type from the value assigned to the attribute `self`
+	#
+	# Return the static type if it can be safely inferred.
+	private fun infer_static_type(modelbuilder: ModelBuilder, nexpr: AExpr,
+		mclassdef: MClassDef, mmodule: MModule, mreadpropdef: MPropDef): nullable MType
+	do
+		var mtype = null
+		if nexpr isa ANewExpr then
+			mtype = modelbuilder.resolve_mtype_unchecked(mclassdef, nexpr.n_type, true)
+		else if nexpr isa AAsCastExpr then
+			mtype = modelbuilder.resolve_mtype_unchecked(mclassdef, nexpr.n_type, true)
+		else if nexpr isa AIntegerExpr then
+			var cla: nullable MClass = null
+			if nexpr.value isa Int then
+				cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int")
+			else if nexpr.value isa Byte then
+				cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Byte")
+			else if nexpr.value isa Int8 then
+				cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int8")
+			else if nexpr.value isa Int16 then
+				cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int16")
+			else if nexpr.value isa UInt16 then
+				cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "UInt16")
+			else if nexpr.value isa Int32 then
+				cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int32")
+			else if nexpr.value isa UInt32 then
+				cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "UInt32")
+			else
+				# Should not happen, and should be updated as new types are added
+				abort
+			end
+			if cla != null then mtype = cla.mclass_type
+		else if nexpr isa AFloatExpr then
+			var cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Float")
+			if cla != null then mtype = cla.mclass_type
+		else if nexpr isa ACharExpr then
+			var cla: nullable MClass
+			if nexpr.is_ascii then
+				cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Byte")
+			else if nexpr.is_code_point then
+				cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Int")
+			else
+				cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Char")
+			end
+			if cla != null then mtype = cla.mclass_type
+		else if nexpr isa ABoolExpr then
+			var cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Bool")
+			if cla != null then mtype = cla.mclass_type
+		else if nexpr isa ASuperstringExpr then
+			var cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "String")
+			if cla != null then mtype = cla.mclass_type
+		else if nexpr isa AStringFormExpr then
+			var cla: nullable MClass
+			if nexpr.is_bytestring then
+				cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Bytes")
+			else if nexpr.is_re then
+				cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "Regex")
+			else if nexpr.is_string then
+				cla = modelbuilder.try_get_mclass_by_name(nexpr, mmodule, "String")
+			else
+				abort
+			end
+			if cla != null then mtype = cla.mclass_type
+		else if nexpr isa AArrayExpr and nexpr.n_type == null and nexpr.n_exprs.not_empty then
+			# Non-empty arrays without an explicit type
+
+			var item_mtypes = new Set[MType]
+			var fails = false
+			for node in nexpr.n_exprs do
+				var item_mtype = infer_static_type(modelbuilder, node, mclassdef, mmodule, mreadpropdef)
+				if item_mtype == null then
+					fails = true
+				else
+					item_mtypes.add item_mtype
+				end
+			end
+
+			if fails then return null # Failed to infer some types
+
+			if item_mtypes.length > 1 then
+				modelbuilder.error(self, "Type Error: ambiguous array type {item_mtypes.join(" ")}")
+			end
+
+			mtype = mmodule.array_type(item_mtypes.first)
+		else if nexpr isa AUminusExpr and (nexpr.n_expr isa AIntegerExpr or nexpr.n_expr isa AFloatExpr) then
+			# The Int and Float unary - is defined in `kernel`, so this may
+			# result in an invalid behavior when using a custom kernel.
+			# A workaround is to declare the attribute static type.
+			# This is still very useful, especially to novice programmers.
+			mtype = infer_static_type(modelbuilder, nexpr.n_expr, mclassdef, mmodule, mreadpropdef)
+		else if nexpr isa AOnceExpr then
+			mtype = infer_static_type(modelbuilder, nexpr.n_expr, mclassdef, mmodule, mreadpropdef)
+		else
+			modelbuilder.error(self, "Error: untyped attribute `{mreadpropdef}`. Implicit typing allowed only for literals and new.")
+		end
+		return mtype
+	end
+
 	redef fun check_signature(modelbuilder)
 	do
 		var mpropdef = self.mpropdef

tests/sav/test_attr_infer_type_alt1.res

@@ -0,0 +1,4 @@
+alt/test_attr_infer_type_alt1.nit:23,5--6: Type Error: ambiguous array type Int Float String
+alt/test_attr_infer_type_alt1.nit:24,5--6: Error: untyped attribute `test_attr_infer_type_alt1$A$a2`. Implicit typing allowed only for literals and new.
+alt/test_attr_infer_type_alt1.nit:25,5--6: Error: untyped attribute `test_attr_infer_type_alt1$A$a4`. Implicit typing allowed only for literals and new.
+alt/test_attr_infer_type_alt1.nit:27,5--6: Type Error: ambiguous array type Int String

tests/test_attr_infer_type.nit

@@ -0,0 +1,30 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import collection
+import text
+
+class A
+	var i0 = 0
+	var i1 = -1
+	var f = -1.0
+	var a0 = [0, 1]
+#alt1#	var a1 = [0, 1.0, "a"] # Different types
+#alt1#	var a2 = [0, 1: Int] # Can't reliably check subtypes
+#alt1#	var a4 = [1+1] # Expression
+	var o0 = once [0, 2]
+#alt1#	var o1 = once [0, "a"] # Forwarded error
+end
+
+var a = new A