internal/lsp/completion: fix untyped int type inference

For index expressions, optional "make" args, and composite literal
slice/array keys, we were inferring an expected type of int instead of
untyped int. This caused candidate rankings to not be quite right in
general, and in particular, after support for automatic type
conversions was added, the issue manifested as:

    var foo []int
    var bar int32
    foo[ba<>] // completed to "int(bar)" instead of "bar"

Fixes golang/go#43375.

Change-Id: I6daef7d23b767f296bdbbc8f47f5b2c972ad9b80
Reviewed-on: https://go-review.googlesource.com/c/tools/+/289272
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
Trust: Rebecca Stambler <rstambler@golang.org>
Trust: Hyang-Ah Hana Kim <hyangah@gmail.com>

internal/lsp/source/completion/builtin.go

@@ -127,7 +127,7 @@ func (c *completer) builtinArgType(obj types.Object, call *ast.CallExpr, parentI
 			inf.typeName.wantTypeName = true
 			inf.objType = parentInf.objType
 		} else {
-			inf.objType = types.Typ[types.Int]
+			inf.objType = types.Typ[types.UntypedInt]
 		}
 	}
 

internal/lsp/source/completion/completion.go

@@ -1690,12 +1690,12 @@ func (c *completer) expectedCompositeLiteralType() types.Type {
 	switch t := clInfo.clType.(type) {
 	case *types.Slice:
 		if clInfo.inKey {
-			return types.Typ[types.Int]
+			return types.Typ[types.UntypedInt]
 		}
 		return t.Elem()
 	case *types.Array:
 		if clInfo.inKey {
-			return types.Typ[types.Int]
+			return types.Typ[types.UntypedInt]
 		}
 		return t.Elem()
 	case *types.Map:
@@ -2038,7 +2038,7 @@ Nodes:
 		case *ast.SliceExpr:
 			// Make sure position falls within the brackets (e.g. "foo[a:<>]").
 			if node.Lbrack < c.pos && c.pos <= node.Rbrack {
-				inf.objType = types.Typ[types.Int]
+				inf.objType = types.Typ[types.UntypedInt]
 			}
 			return inf
 		case *ast.IndexExpr:
@@ -2049,7 +2049,7 @@ Nodes:
 					case *types.Map:
 						inf.objType = t.Key()
 					case *types.Slice, *types.Array:
-						inf.objType = types.Typ[types.Int]
+						inf.objType = types.Typ[types.UntypedInt]
 					}
 				}
 			}

internal/lsp/testdata/builtins/builtin_args.go

@@ -43,6 +43,10 @@ func _() {
 	make()              //@rank(")", builtinMapType, int),rank(")", builtinChanType, int),rank(")", builtinSliceType, int),rank(")", builtinMapType, int)
 	make(aSliceType, a) //@rank(")", builtinInt, builtinSlice)
 
+	type myInt int
+	var mi myInt        //@item(builtinMyInt, "mi", "myInt", "var")
+	make(aSliceType, m) //@snippet(")", builtinMyInt, "mi", "mi")
+
 	var _ []int = make() //@rank(")", builtinSliceType, builtinMapType)
 
 	type myStruct struct{}  //@item(builtinStructType, "myStruct", "struct{...}", "struct")

internal/lsp/testdata/index/index.go

@@ -18,4 +18,8 @@ func _() {
 	type myMap map[string]int
 	var baz myMap
 	baz[a] //@complete("]", indexAA, indexAB)
+
+	type myInt int
+	var mi myInt //@item(indexMyInt, "mi", "myInt", "var")
+	foo[m]       //@snippet("]", indexMyInt, "mi", "mi")
 }

internal/lsp/testdata/summary.txt.golden

@@ -2,7 +2,7 @@
 CallHierarchyCount = 2
 CodeLensCount = 5
 CompletionsCount = 258
-CompletionSnippetCount = 90
+CompletionSnippetCount = 92
 UnimportedCompletionsCount = 5
 DeepCompletionsCount = 5
 FuzzyCompletionsCount = 8