internal/lsp/source: fix function completion ranking

I noticed an annoying completion ranking issue:

   // ranks "HandlerFunc" over "HandleFunc"
   http.HandleFunc<>

This was due to us downranking function calls to prefer fields/vars. I
tweaked the logic to only downrank methods (with a receiver).

Change-Id: Ia4040dc8a35f641be2d7d934bf555090831219ac
Reviewed-on: https://go-review.googlesource.com/c/tools/+/246357
Run-TryBot: Muir Manders <muir@mnd.rs>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

internal/lsp/source/completion.go

@@ -340,9 +340,11 @@ func (c *completer) found(ctx context.Context, cand candidate) {
 		}
 	}
 
-	// Lower score of function calls so we prefer fields and vars over calls.
+	// Lower score of method calls so we prefer fields and vars over calls.
 	if cand.expandFuncCall {
-		cand.score *= 0.9
+		if sig, ok := obj.Type().Underlying().(*types.Signature); ok && sig.Recv() != nil {
+			cand.score *= 0.9
+		}
 	}
 
 	// Prefer private objects over public ones.

internal/lsp/testdata/lsp/primarymod/bad/bad1.go

@@ -8,7 +8,7 @@ type stateFunc func() stateFunc //@item(stateFunc, "stateFunc", "func() stateFun
 var a unknown //@item(global_a, "a", "unknown", "var"),diag("unknown", "compiler", "undeclared name: unknown", "error")
 
 func random() int { //@item(random, "random", "func() int", "func")
-	//@complete("", global_a, bob, stateFunc, random, random2, random3, stuff)
+	//@complete("", global_a, bob, random, random2, random3, stateFunc, stuff)
 	return 0
 }
 
@@ -16,18 +16,18 @@ func random2(y int) int { //@item(random2, "random2", "func(y int) int", "func")
 	x := 6       //@item(x, "x", "int", "var"),diag("x", "compiler", "x declared but not used", "error")
 	var q blah   //@item(q, "q", "blah", "var"),diag("q", "compiler", "q declared but not used", "error"),diag("blah", "compiler", "undeclared name: blah", "error")
 	var t **blob //@item(t, "t", "**blob", "var"),diag("t", "compiler", "t declared but not used", "error"),diag("blob", "compiler", "undeclared name: blob", "error")
-	//@complete("", q, t, x, bad_y_param, global_a, bob, stateFunc, random, random2, random3, stuff)
+	//@complete("", q, t, x, bad_y_param, global_a, bob, random, random2, random3, stateFunc, stuff)
 
 	return y
 }
 
 func random3(y ...int) { //@item(random3, "random3", "func(y ...int)", "func"),item(y_variadic_param, "y", "[]int", "var")
-	//@complete("", y_variadic_param, global_a, bob, stateFunc, random, random2, random3, stuff)
+	//@complete("", y_variadic_param, global_a, bob, random, random2, random3, stateFunc, stuff)
 
 	var ch chan (favType1)   //@item(ch, "ch", "chan (favType1)", "var"),diag("ch", "compiler", "ch declared but not used", "error"),diag("favType1", "compiler", "undeclared name: favType1", "error")
 	var m map[keyType]int    //@item(m, "m", "map[keyType]int", "var"),diag("m", "compiler", "m declared but not used", "error"),diag("keyType", "compiler", "undeclared name: keyType", "error")
 	var arr []favType2       //@item(arr, "arr", "[]favType2", "var"),diag("arr", "compiler", "arr declared but not used", "error"),diag("favType2", "compiler", "undeclared name: favType2", "error")
 	var fn1 func() badResult //@item(fn1, "fn1", "func() badResult", "var"),diag("fn1", "compiler", "fn1 declared but not used", "error"),diag("badResult", "compiler", "undeclared name: badResult", "error")
 	var fn2 func(badParam)   //@item(fn2, "fn2", "func(badParam)", "var"),diag("fn2", "compiler", "fn2 declared but not used", "error"),diag("badParam", "compiler", "undeclared name: badParam", "error")
-	//@complete("", arr, ch, fn1, fn2, m, y_variadic_param, global_a, bob, stateFunc, random, random2, random3, stuff)
+	//@complete("", arr, ch, fn1, fn2, m, y_variadic_param, global_a, bob, random, random2, random3, stateFunc, stuff)
 }

internal/lsp/testdata/lsp/primarymod/badstmt/badstmt.go.in

@@ -20,6 +20,7 @@ func _() {
 func _() {
 	defer func() {
 		foo.F //@complete(" //", Foo),snippet(" //", Foo, "Foo()", "Foo()")
-		foo. //@complete(" //", IntFoo, StructFoo, Foo)
+
+		foo. //@rank(" //", Foo)
 	}
 }

internal/lsp/testdata/lsp/primarymod/badstmt/badstmt_2.go.in

@@ -5,5 +5,5 @@ import (
 )
 
 func _() {
-	defer func() { foo. } //@complete(" }", IntFoo, StructFoo, Foo)
+	defer func() { foo. } //@rank(" }", Foo)
 }

internal/lsp/testdata/lsp/primarymod/badstmt/badstmt_3.go.in

@@ -5,5 +5,5 @@ import (
 )
 
 func _() {
-	go foo. //@complete(" //", IntFoo, StructFoo, Foo)
+	go foo. //@rank(" //", Foo)
 }

internal/lsp/testdata/lsp/primarymod/badstmt/badstmt_4.go.in

@@ -6,6 +6,6 @@ import (
 
 func _() {
 	go func() {
-		defer foo. //@complete(" //", IntFoo, StructFoo, Foo)
+		defer foo. //@rank(" //", Foo)
 	}
 }

internal/lsp/testdata/lsp/primarymod/bar/bar.go.in

@@ -15,9 +15,9 @@ func _() {
 
 // Bar is a function.
 func Bar() { //@item(Bar, "Bar", "func()", "func", "Bar is a function.")
-	foo.Foo()        //@complete("F", IntFoo, StructFoo, Foo)
+	foo.Foo()        //@complete("F", Foo, IntFoo, StructFoo)
 	var _ foo.IntFoo //@complete("I", IntFoo, StructFoo)
-	foo.()           //@complete("(", IntFoo, StructFoo, Foo)
+	foo.()           //@complete("(", Foo, IntFoo, StructFoo)
 }
 
 func _() {

internal/lsp/testdata/lsp/primarymod/deep/deep.go

@@ -129,7 +129,7 @@ type baz struct {
 }
 
 func (b baz) _() {
-	b.Thing().val //@item(deepBazMethVal, "b.Thing().val", "int", "field")
-	b.thing.val   //@item(deepBazFieldVal, "b.thing.val", "int", "field")
-	var _ int = b //@rank(" //", deepBazFieldVal, deepBazMethVal)
+	b.Thing().val    //@item(deepBazMethVal, "b.Thing().val", "int", "field")
+	b.thing.val      //@item(deepBazFieldVal, "b.thing.val", "int", "field")
+	var _ int = bval //@rank(" //", deepBazFieldVal, deepBazMethVal)
 }

internal/lsp/testdata/lsp/primarymod/func_rank/func_rank.go.in

@@ -1,5 +1,7 @@
 package func_rank
 
+import "net/http"
+
 var stringAVar = "var"    //@item(stringAVar, "stringAVar", "string", "var")
 func stringBFunc() string { return "str" } //@item(stringBFunc, "stringBFunc", "func() string", "func")
 type stringer struct{}    //@item(stringer, "stringer", "struct{...}", "struct")
@@ -59,3 +61,10 @@ func (foo) FooPublicMethod() int { //@item(rankFooPubMeth, "FooPublicMethod", "f
 func _() {
 	var _ int = foo{}. //@rank(" //", rankFooPrivField, rankFooPubField),rank(" //", rankFooPrivMeth, rankFooPubMeth),rank(" //", rankFooPrivField, rankFooPrivMeth)
 }
+
+func _() {
+	HandleFunc //@item(httpHandleFunc, "HandleFunc", "func(pattern string, handler func(ResponseWriter, *Request))", "func")
+	HandlerFunc //@item(httpHandlerFunc, "HandlerFunc", "func(http.ResponseWriter, *http.Request)", "type")
+
+	http.HandleFunc //@rank(" //", httpHandleFunc, httpHandlerFunc)
+}

internal/lsp/testdata/lsp/primarymod/nodisk/nodisk.overlay.go

@@ -5,5 +5,5 @@ import (
 )
 
 func _() {
-	foo.Foo() //@complete("F", IntFoo, StructFoo, Foo)
+	foo.Foo() //@complete("F", Foo, IntFoo, StructFoo)
 }

internal/lsp/testdata/lsp/summary.txt.golden

@@ -1,11 +1,11 @@
 -- summary --
 CodeLensCount = 4
-CompletionsCount = 245
+CompletionsCount = 241
 CompletionSnippetCount = 80
 UnimportedCompletionsCount = 6
 DeepCompletionsCount = 5
 FuzzyCompletionsCount = 8
-RankedCompletionsCount = 122
+RankedCompletionsCount = 127
 CaseSensitiveCompletionsCount = 4
 DiagnosticsCount = 44
 FoldingRangesCount = 2