fix some typos in comments, remove some redundants and some always not nil checks

src/go/internal/srcimporter/srcimporter.go

@@ -30,7 +30,7 @@ type Importer struct {
 	packages map[string]*types.Package
 }
 
-// NewImporter returns a new Importer for the given context, file set, and map
+// New returns a new Importer for the given context, file set, and map
 // of packages. The context is used to resolve import paths to package paths,
 // and identifying the files belonging to the package. If the context provides
 // non-nil file system functions, they are used instead of the regular package

src/go/parser/error_test.go

@@ -90,7 +90,7 @@ func expectedErrors(fset *token.FileSet, filename string, src []byte) map[token.
 				if s[1] == "HERE" {
 					pos = here
 				}
-				errors[pos] = string(s[2])
+				errors[pos] = s[2]
 			}
 		case token.SEMICOLON:
 			// don't use the position of auto-inserted (invisible) semicolons

src/go/parser/parser.go

@@ -891,7 +891,7 @@ func (p *parser) parseParameters(acceptTParams bool) (tparams, params *ast.Field
 		rbrack := p.expect(token.RBRACK)
 		tparams = &ast.FieldList{Opening: opening, List: list, Closing: rbrack}
 		// Type parameter lists must not be empty.
-		if tparams != nil && tparams.NumFields() == 0 {
+		if tparams.NumFields() == 0 {
 			p.error(tparams.Closing, "empty type parameter list")
 			tparams = nil // avoid follow-on errors
 		}

src/go/printer/printer.go

@@ -844,7 +844,7 @@ func (p *printer) writeWhitespace(n int) {
 // ----------------------------------------------------------------------------
 // Printing interface
 
-// nlines limits n to maxNewlines.
+// nlimit limits n to maxNewlines.
 func nlimit(n int) int {
 	if n > maxNewlines {
 		n = maxNewlines

src/go/scanner/errors.go

@@ -86,7 +86,7 @@ func (p *ErrorList) RemoveMultiples() {
 			i++
 		}
 	}
-	(*p) = (*p)[0:i]
+	*p = (*p)[0:i]
 }
 
 // An ErrorList implements the error interface.

src/go/scanner/scanner.go

@@ -383,7 +383,7 @@ func (s *Scanner) digits(base int, invalid *int) (digsep int) {
 			if s.ch == '_' {
 				ds = 2
 			} else if s.ch >= max && *invalid < 0 {
-				*invalid = int(s.offset) // record invalid rune offset
+				*invalid = s.offset // record invalid rune offset
 			}
 			digsep |= ds
 			s.next()

src/go/types/infer.go

@@ -215,7 +215,7 @@ func (check *Checker) infer(posn positioner, tparams []*TypeName, targs []Type,
 	}
 
 	// At least one type argument couldn't be inferred.
-	assert(targs != nil && index >= 0 && targs[index] == nil)
+	assert(index >= 0 && targs[index] == nil)
 	tpar := tparams[index]
 	if report {
 		check.errorf(posn, _Todo, "cannot infer %s (%v) (%v)", tpar.name, tpar.pos, targs)