cmd/compile: fix compilation of inferred type arguments

Previously, type arguments could only be inferred for generic
functions in call expressions, whereas with the reverse type inference
proposal they can now be inferred in assignment contexts too. As a
consequence, we now need to check Info.Instances to find the inferred
type for more cases now.

Updates #59338.
Fixes #59955.

Change-Id: I9b6465395869459c2387d0424febe7337b28b90e
Reviewed-on: https://go-review.googlesource.com/c/go/+/492455
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>

diff --git a/src/cmd/compile/internal/noder/writer.go b/src/cmd/compile/internal/noder/writer.go
index 72c7a1fc8649cbfc12ba539ecf40d97995696560..178c3eb1a9c022d8d33da598a35d7c87f4e0a36e 100644 (file)
--- a/src/cmd/compile/internal/noder/writer.go
+++ b/src/cmd/compile/internal/noder/writer.go
@@ -123,14 +123,25 @@ func (pw *pkgWriter) unexpected(what string, p poser) {
 }
 
 func (pw *pkgWriter) typeAndValue(x syntax.Expr) syntax.TypeAndValue {
-       tv := x.GetTypeInfo()
-       if tv.Type == nil {
+       tv, ok := pw.maybeTypeAndValue(x)
+       if !ok {
                pw.fatalf(x, "missing Types entry: %v", syntax.String(x))
        }
        return tv
 }
+
 func (pw *pkgWriter) maybeTypeAndValue(x syntax.Expr) (syntax.TypeAndValue, bool) {
        tv := x.GetTypeInfo()
+
+       // If x is a generic function whose type arguments are inferred
+       // from assignment context, then we need to find its inferred type
+       // in Info.Instances instead.
+       if name, ok := x.(*syntax.Name); ok {
+               if inst, ok := pw.info.Instances[name]; ok {
+                       tv.Type = inst.Type
+               }
+       }
+
        return tv, tv.Type != nil
 }
 

diff --git a/test/fixedbugs/issue59338.go b/test/fixedbugs/issue59338.go
index dc8604f31967a956552fc77862dc0516df9e4b9a..8ba3fd2b3b911dadb87d5375e060bbfb7c487645 100644 (file)
--- a/test/fixedbugs/issue59338.go
+++ b/test/fixedbugs/issue59338.go
@@ -21,15 +21,13 @@ func main() {
                panic(2)
        }
 
-       // Disabled for now - requires some noder work
-       // TODO fix this
-       // if g3(g1, 3) != g1(3) {
-       //      panic(3)
-       // }
-
-       // if g4(g2, 4) != "" {
-       //      panic(4)
-       // }
+       if g3(g1, 3) != g1(3) {
+               panic(3)
+       }
+
+       if g4(g2, 4) != "" {
+               panic(4)
+       }
 }
 
 func g1[P any](x P) P    { return x }