From cf5d73e8a2ba8d382278c7f490db61e513768159 Mon Sep 17 00:00:00 2001 From: Russ Cox Date: Tue, 18 Jan 2022 10:31:59 -0500 Subject: [PATCH] cmd/compile, go/types: restore 'too many return values' error for func with no results Currently the code handles the case of returning values from a function with no result parameters as a special case. Consider this input: package p func f0_2() { return 1, 2 } func f0_1() { return 1 } func f1_0() int { return } func f1_2() int { return 1, 2 } func f2_0() (int, int) { return } func f2_1() (int, int) { return 1 } The errors are: x.go:3:33: no result values expected <<< x.go:4:33: no result values expected <<< x.go:5:26: not enough return values have () want (int) x.go:6:36: too many return values have (number, number) want (int) x.go:7:26: not enough return values have () want (int, int) x.go:8:33: not enough return values have (number) want (int, int) There are two problems with the current special case emitting the errors on the marked line: 1. It calls them 'result values' instead of 'return values'. 2. It doesn't show the type being returned, which can be useful to programmers. Using the general case solves both these problems, so this CL removes the special case and calls the general case instead. Now those two errors read: x.go:3:33: too many return values have (number, number) want () x.go:4:33: too many return values have (number) want () Fixes #50653. Change-Id: If6b47dcece14ed4febb3a2d3d78270d5be1cb24d Reviewed-on: https://go-review.googlesource.com/c/go/+/379116 Trust: Russ Cox Run-TryBot: Russ Cox Reviewed-by: Robert Griesemer TryBot-Result: Gopher Robot --- src/cmd/compile/internal/types2/stmt.go | 40 +++++++++---------- .../internal/types2/testdata/check/stmt0.src | 2 +- .../types2/testdata/check/vardecl.src | 4 +- src/go/types/stmt.go | 36 ++++++++--------- src/go/types/testdata/check/stmt0.src | 2 +- src/go/types/testdata/check/vardecl.src | 4 +- test/fixedbugs/issue4215.go | 2 +- test/fixedbugs/issue48834.go | 2 +- 8 files changed, 44 insertions(+), 48 deletions(-) diff --git a/src/cmd/compile/internal/types2/stmt.go b/src/cmd/compile/internal/types2/stmt.go index 98244cd5e9..b23d7aeef2 100644 --- a/src/cmd/compile/internal/types2/stmt.go +++ b/src/cmd/compile/internal/types2/stmt.go @@ -474,30 +474,28 @@ func (check *Checker) stmt(ctxt stmtContext, s syntax.Stmt) { case *syntax.ReturnStmt: res := check.sig.results + // Return with implicit results allowed for function with named results. + // (If one is named, all are named.) results := unpackExpr(s.Results) - if res.Len() > 0 { - // function returns results - // (if one, say the first, result parameter is named, all of them are named) - if len(results) == 0 && res.vars[0].name != "" { - // spec: "Implementation restriction: A compiler may disallow an empty expression - // list in a "return" statement if a different entity (constant, type, or variable) - // with the same name as a result parameter is in scope at the place of the return." - for _, obj := range res.vars { - if alt := check.lookup(obj.name); alt != nil && alt != obj { - var err error_ - err.errorf(s, "result parameter %s not in scope at return", obj.name) - err.errorf(alt, "inner declaration of %s", obj) - check.report(&err) - // ok to continue - } + if len(results) == 0 && res.Len() > 0 && res.vars[0].name != "" { + // spec: "Implementation restriction: A compiler may disallow an empty expression + // list in a "return" statement if a different entity (constant, type, or variable) + // with the same name as a result parameter is in scope at the place of the return." + for _, obj := range res.vars { + if alt := check.lookup(obj.name); alt != nil && alt != obj { + var err error_ + err.errorf(s, "result parameter %s not in scope at return", obj.name) + err.errorf(alt, "inner declaration of %s", obj) + check.report(&err) + // ok to continue } - } else { - // return has results or result parameters are unnamed - check.initVars(res.vars, results, s) } - } else if len(results) > 0 { - check.error(results[0], "no result values expected") - check.use(results...) + } else { + var lhs []*Var + if res.Len() > 0 { + lhs = res.vars + } + check.initVars(lhs, results, s) } case *syntax.BranchStmt: diff --git a/src/cmd/compile/internal/types2/testdata/check/stmt0.src b/src/cmd/compile/internal/types2/testdata/check/stmt0.src index c4820c9f7f..ed7ce05327 100644 --- a/src/cmd/compile/internal/types2/testdata/check/stmt0.src +++ b/src/cmd/compile/internal/types2/testdata/check/stmt0.src @@ -375,7 +375,7 @@ func continues() { func returns0() { return - return 0 /* ERROR no result values expected */ + return 0 /* ERROR too many return values */ } func returns1(x float64) (int, *float64) { diff --git a/src/cmd/compile/internal/types2/testdata/check/vardecl.src b/src/cmd/compile/internal/types2/testdata/check/vardecl.src index 827b9b9d69..c3fe61c3d4 100644 --- a/src/cmd/compile/internal/types2/testdata/check/vardecl.src +++ b/src/cmd/compile/internal/types2/testdata/check/vardecl.src @@ -177,8 +177,8 @@ func _() { func _() { var x int - return x /* ERROR no result values expected */ - return math /* ERROR no result values expected */ .Sin(0) + return x /* ERROR too many return values */ + return math /* ERROR too many return values */ .Sin(0) } func _() int { diff --git a/src/go/types/stmt.go b/src/go/types/stmt.go index 0a69789078..802673567d 100644 --- a/src/go/types/stmt.go +++ b/src/go/types/stmt.go @@ -503,27 +503,25 @@ func (check *Checker) stmt(ctxt stmtContext, s ast.Stmt) { case *ast.ReturnStmt: res := check.sig.results - if res.Len() > 0 { - // function returns results - // (if one, say the first, result parameter is named, all of them are named) - if len(s.Results) == 0 && res.vars[0].name != "" { - // spec: "Implementation restriction: A compiler may disallow an empty expression - // list in a "return" statement if a different entity (constant, type, or variable) - // with the same name as a result parameter is in scope at the place of the return." - for _, obj := range res.vars { - if alt := check.lookup(obj.name); alt != nil && alt != obj { - check.errorf(s, _OutOfScopeResult, "result parameter %s not in scope at return", obj.name) - check.errorf(alt, _OutOfScopeResult, "\tinner declaration of %s", obj) - // ok to continue - } + // Return with implicit results allowed for function with named results. + // (If one is named, all are named.) + if len(s.Results) == 0 && res.Len() > 0 && res.vars[0].name != "" { + // spec: "Implementation restriction: A compiler may disallow an empty expression + // list in a "return" statement if a different entity (constant, type, or variable) + // with the same name as a result parameter is in scope at the place of the return." + for _, obj := range res.vars { + if alt := check.lookup(obj.name); alt != nil && alt != obj { + check.errorf(s, _OutOfScopeResult, "result parameter %s not in scope at return", obj.name) + check.errorf(alt, _OutOfScopeResult, "\tinner declaration of %s", obj) + // ok to continue } - } else { - // return has results or result parameters are unnamed - check.initVars(res.vars, s.Results, s) } - } else if len(s.Results) > 0 { - check.error(s.Results[0], _WrongResultCount, "no result values expected") - check.use(s.Results...) + } else { + var lhs []*Var + if res.Len() > 0 { + lhs = res.vars + } + check.initVars(lhs, s.Results, s) } case *ast.BranchStmt: diff --git a/src/go/types/testdata/check/stmt0.src b/src/go/types/testdata/check/stmt0.src index a635af7cbb..ec8bf71013 100644 --- a/src/go/types/testdata/check/stmt0.src +++ b/src/go/types/testdata/check/stmt0.src @@ -375,7 +375,7 @@ func continues() { func returns0() { return - return 0 /* ERROR no result values expected */ + return 0 /* ERROR too many return values */ } func returns1(x float64) (int, *float64) { diff --git a/src/go/types/testdata/check/vardecl.src b/src/go/types/testdata/check/vardecl.src index 787f7878f1..56abf97722 100644 --- a/src/go/types/testdata/check/vardecl.src +++ b/src/go/types/testdata/check/vardecl.src @@ -169,8 +169,8 @@ func _() { func _() { var x int - return x /* ERROR no result values expected */ - return math /* ERROR no result values expected */ .Sin(0) + return x /* ERROR too many return values */ + return math /* ERROR too many return values */ .Sin(0) } func _() int { diff --git a/test/fixedbugs/issue4215.go b/test/fixedbugs/issue4215.go index b6ece4bf21..9f32f5b100 100644 --- a/test/fixedbugs/issue4215.go +++ b/test/fixedbugs/issue4215.go @@ -11,7 +11,7 @@ func foo() (int, int) { } func foo2() { - return int(2), 2 // ERROR "too many arguments to return\n\thave \(int, number\)\n\twant \(\)|return with value in function with no return type|no result values expected" + return int(2), 2 // ERROR "too many (arguments to return|return values)\n\thave \(int, number\)\n\twant \(\)|return with value in function with no return type" } func foo3(v int) (a, b, c, d int) { diff --git a/test/fixedbugs/issue48834.go b/test/fixedbugs/issue48834.go index cf97d132c3..584dfa5764 100644 --- a/test/fixedbugs/issue48834.go +++ b/test/fixedbugs/issue48834.go @@ -20,5 +20,5 @@ func _() int { } func _() { - return 1 // ERROR "too many arguments to return\n\thave \(number\)\n\twant \(\)|no result values expected" + return 1 // ERROR "too many (arguments to return|return values)\n\thave \(number\)\n\twant \(\)" }