internal/lsp: use the explicit import spec name as ident

When there is an explicit name for an import spec, treat it as its own
identifier, separate from the import path.

Example:
	import h "hello"

The name h is defined in that import spec, not in the package hello
it contains its own references. If asked about a position within the
import path, continue treating that as referencing the imported package.
If the position is within the name, use the identifier there that is
local to that file.

This change allows for go to definition of the explicit name to point to
itself, find all references from the import spec, and rename the
explicit name from the import spec.

Change-Id: Ia1d927a26e73f2dc450d256d71909c006bdf4c37
Reviewed-on: https://go-review.googlesource.com/c/tools/+/191164
Run-TryBot: Suzy Mueller <suzmue@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Cottrell <iancottrell@google.com>

internal/lsp/source/identifier.go

@@ -282,7 +282,7 @@ func objToNode(ctx context.Context, view View, originPkg *types.Package, obj typ
 func importSpec(ctx context.Context, f GoFile, fAST *ast.File, pkg Package, pos token.Pos) (*IdentifierInfo, error) {
 	var imp *ast.ImportSpec
 	for _, spec := range fAST.Imports {
-		if spec.Pos() <= pos && pos < spec.End() {
+		if spec.Path.Pos() <= pos && pos < spec.Path.End() {
 			imp = spec
 		}
 	}

internal/lsp/testdata/godef/a/a.go.golden

@@ -67,8 +67,8 @@ godef/a/a.go:14:6-9: defined here as var err error
 
 -- err-hover --
 var err error
--- string-hover --
-string
 -- make-hover --
 The make built-in function allocates and initializes an object of type slice, map, or chan (only).
 func(t Type, size ...IntegerType) Type
+-- string-hover --
+string

internal/lsp/testdata/godef/a/f.go.golden

@@ -1,3 +1,27 @@
+-- switchStringY-definition --
+godef/a/f.go:8:9-10: defined here as var y string
+
+-- switchStringY-definition-json --
+{
+	"span": {
+		"uri": "file://godef/a/f.go",
+		"start": {
+			"line": 8,
+			"column": 9,
+			"offset": 76
+		},
+		"end": {
+			"line": 8,
+			"column": 10,
+			"offset": 77
+		}
+	},
+	"description": "var y string"
+}
+
+
+-- switchStringY-hover --
+var y string
 -- switchY-definition --
 godef/a/f.go:8:9-10: defined here as var y int
 
@@ -22,27 +46,3 @@ godef/a/f.go:8:9-10: defined here as var y int
 
 -- switchY-hover --
 var y int
--- switchStringY-definition --
-godef/a/f.go:8:9-10: defined here as var y string
-
--- switchStringY-definition-json --
-{
-	"span": {
-		"uri": "file://godef/a/f.go",
-		"start": {
-			"line": 8,
-			"column": 9,
-			"offset": 76
-		},
-		"end": {
-			"line": 8,
-			"column": 10,
-			"offset": 77
-		}
-	},
-	"description": "var y string"
-}
-
-
--- switchStringY-hover --
-var y string

internal/lsp/testdata/godef/b/b.go

@@ -1,7 +1,7 @@
 package b
 
 import (
-	myFoo "golang.org/x/tools/internal/lsp/foo" //@godef("foo", PackageFoo),godef("myFoo", PackageFoo)
+	myFoo "golang.org/x/tools/internal/lsp/foo" //@mark(myFoo, "myFoo"),godef("foo", PackageFoo),godef("myFoo", myFoo)
 	"golang.org/x/tools/internal/lsp/godef/a"   //@mark(AImport, "\"")
 )
 
@@ -31,5 +31,5 @@ func Bar() {
 	_ = x.F2    //@godef("F2", S2F2)
 	_ = x.S2.F1 //@godef("F1", S2F1)
 
-	var _ *myFoo.StructFoo
+	var _ *myFoo.StructFoo //@godef("myFoo", myFoo)
 }

internal/lsp/testdata/godef/b/b.go.golden

@@ -66,7 +66,7 @@ foo/foo.go:1:9-12: defined here as
 }
 
 -- PackageFoo-hover --
-myFoo "golang.org/x/tools/internal/lsp/foo" //@godef("foo", PackageFoo),godef("myFoo", PackageFoo)
+myFoo "golang.org/x/tools/internal/lsp/foo" //@mark(myFoo, "myFoo"),godef("foo", PackageFoo),godef("myFoo", myFoo)
 
 -- S1-definition --
 godef/b/b.go:8:6-8: defined here as S1 struct {
@@ -249,3 +249,5 @@ godef/a/a.go:9:6-11: defined here as func a.Stuff()
 
 -- Stuff-hover --
 func a.Stuff()
+-- myFoo-hover --
+package myFoo ("golang.org/x/tools/internal/lsp/foo")

internal/lsp/tests/tests.go

@@ -34,7 +34,7 @@ const (
 	ExpectedDiagnosticsCount       = 21
 	ExpectedFormatCount            = 6
 	ExpectedImportCount            = 2
-	ExpectedDefinitionsCount       = 38
+	ExpectedDefinitionsCount       = 39
 	ExpectedTypeDefinitionsCount   = 2
 	ExpectedHighlightsCount        = 2
 	ExpectedReferencesCount        = 5