Re: Go patch committed: Move lowering pass after check types pass

[Ian Lance Taylor <iant@golang.org>]

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On Mon, Dec 18, 2023 at 5:32 PM Ian Lance Taylor <iant@golang.org> wrote:
>
> This Go frontend patch moves the lowering pass after the type
> determination and the type checking passes.  This lets us simplify
> some of the code that determines the type of an expression, which
> previously had to work correctly both before and after type
> determination.
>
> I'm doing this to help with future generic support.  For example, with
> generics, we can see code like
>
>     func ident[T any](v T) T { return v }
>
>     func F() int32 {
>         s := int32(1)
>         return ident(s)
>     }
>
> Before this change, we would type check return statements in the
> lowering pass (see Return_statement::do_lower).  With a generic
> example like the above, that means we have to determine the type of s,
> and use that to infer the type arguments passed to ident, and use that
> to determine the result type of ident.  That is too much to do at
> lowering time.  Of course we can change the way that return statements
> work, but similar issues arise with index expressions, the types of
> closures for function literals, and probably other cases as well.
>
> Rather than try to deal with all those cases, we move the lowering
> pass after type checking.  This requires a bunch of changes, notably
> for determining constant types.  We have to add type checking for
> various constructs that formerly disappeared in the lowering pass. So
> it's a lot of shuffling.  Sorry for the size of the patch.
>
> Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.  Committed
> to mainline.

Sorry, I forgot to commit the changes to some of the test files.  I've
committed this patch to fix them.  This fixes PR 113447.

Ian

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3d7820c58f9466a80916dfa50dcdfde457b4c597
diff --git a/gcc/testsuite/go.test/test/fixedbugs/issue20185.go b/gcc/testsuite/go.test/test/fixedbugs/issue20185.go
index 9065868d7f2..24d74f09126 100644
--- a/gcc/testsuite/go.test/test/fixedbugs/issue20185.go
+++ b/gcc/testsuite/go.test/test/fixedbugs/issue20185.go
@@ -10,7 +10,7 @@
 package p
 
 func F() {
-	switch t := nil.(type) { // ERROR "cannot type switch on non-interface value"
+	switch t := nil.(type) { // ERROR "cannot type switch on non-interface value|defined to nil type"
 	default:
 		_ = t
 	}
diff --git a/gcc/testsuite/go.test/test/fixedbugs/issue33386.go b/gcc/testsuite/go.test/test/fixedbugs/issue33386.go
index 7b2f565285e..c5073910a4c 100644
--- a/gcc/testsuite/go.test/test/fixedbugs/issue33386.go
+++ b/gcc/testsuite/go.test/test/fixedbugs/issue33386.go
@@ -18,7 +18,7 @@ func _() {
 
 func _() {
 	defer func() { // no error here about deferred function
-		1 +    // GCCGO_ERROR "value computed is not used"
+		1 +
 	}()            // ERROR "expecting expression|expected operand"
 }
 
diff --git a/gcc/testsuite/go.test/test/fixedbugs/issue4085a.go b/gcc/testsuite/go.test/test/fixedbugs/issue4085a.go
index 200290a081d..f457fcf2b12 100644
--- a/gcc/testsuite/go.test/test/fixedbugs/issue4085a.go
+++ b/gcc/testsuite/go.test/test/fixedbugs/issue4085a.go
@@ -10,9 +10,9 @@ type T []int
 
 func main() {
 	_ = make(T, -1)    // ERROR "negative"
-	_ = make(T, 0.5)   // ERROR "constant 0.5 truncated to integer|non-integer len argument"
+	_ = make(T, 0.5)   // ERROR "truncated to integer|non-integer len argument"
 	_ = make(T, 1.0)   // ok
-	_ = make(T, 1<<63) // ERROR "len argument too large"
+	_ = make(T, 1<<63) // ERROR "integer constant overflow|len argument too large"
 	_ = make(T, 0, -1) // ERROR "negative cap"
 	_ = make(T, 10, 0) // ERROR "len larger than cap"
 }
diff --git a/gcc/testsuite/go.test/test/shift1.go b/gcc/testsuite/go.test/test/shift1.go
index d6a6c38839f..3b1aa9e6900 100644
--- a/gcc/testsuite/go.test/test/shift1.go
+++ b/gcc/testsuite/go.test/test/shift1.go
@@ -189,12 +189,12 @@ func _() {
 	var m1 map[int]string
 	delete(m1, 1<<s)
 	delete(m1, 1.<<s)
-	delete(m1, 1.1<<s) // ERROR "truncated|shift of type float64"
+	delete(m1, 1.1<<s) // ERROR "truncated|shift of type float64|incompatible|non-integer"
 
 	var m2 map[float32]string
-	delete(m2, 1<<s)   // ERROR "invalid|cannot use 1 << s as type float32"
-	delete(m2, 1.<<s)  // ERROR "invalid|cannot use 1 << s as type float32"
-	delete(m2, 1.1<<s) // ERROR "invalid|cannot use 1.1 << s as type float32"
+	delete(m2, 1<<s)   // ERROR "invalid|cannot use 1 << s as type float32|incompatible"
+	delete(m2, 1.<<s)  // ERROR "invalid|cannot use 1 << s as type float32|incompatible"
+	delete(m2, 1.1<<s) // ERROR "invalid|cannot use 1.1 << s as type float32|incompatible"
 }
 
 // shifts of shifts