go/types, types2: enable interface inference

This CL sets enableInterfaceInference to true.
If problems arise due to this during the freeze, revert this CL.

Fixes #41176.
Fixes #57192.

Change-Id: I881ea6842e9c1101b24d9780323c6af365a40d3e
Reviewed-on: https://go-review.googlesource.com/c/go/+/497657
TryBot-Result: Gopher Robot <[email protected]>
Auto-Submit: Robert Griesemer <[email protected]>
Run-TryBot: Robert Griesemer <[email protected]>
Reviewed-by: Robert Findley <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>

src/cmd/compile/internal/types2/unify.go

@@ -56,7 +56,7 @@ const (
 	// If enableInterfaceInference is set, type inference uses
 	// shared methods for improved type inference involving
 	// interfaces.
-	enableInterfaceInference = false
+	enableInterfaceInference = true
 
 	// If traceInference is set, unification will print a trace of its operation.
 	// Interpretation of trace:

src/internal/types/testdata/fixedbugs/issue39976.go

@@ -12,5 +12,5 @@ func NewCache[K, V any](p policy[K, V]) {}
 func _() {
 	var lru LRU[int, string]
 	NewCache[int, string](&lru)
-	NewCache(& /* ERROR "does not match policy[K, V] (cannot infer K and V)" */ lru)
+	NewCache /* ERROR "cannot infer K" */ (&lru)
 }

src/internal/types/testdata/fixedbugs/issue41176.go

@@ -17,5 +17,5 @@ type I[T any] interface {
 func f[T any](x I[T]) {}
 
 func _() {
-	f(S /* ERROR "cannot infer T" */ {})
+	f(S{})
 }

src/internal/types/testdata/fixedbugs/issue53692.go

@@ -11,5 +11,5 @@ type LRU[K comparable, V any] struct{}
 func WithLocking2[K comparable, V any](Cache[K, V]) {}
 
 func _() {
-	WithLocking2[string](LRU /* ERROR "type LRU[string, int] of LRU[string, int]{} does not match inferred type Cache[string, int] for Cache[string, V]" */ [string, int]{})
+	WithLocking2 /* ERROR "cannot infer V" */ [string](LRU[string, int]{})
 }

src/internal/types/testdata/fixedbugs/issue57192.go

@@ -18,5 +18,5 @@ var V2 I2[int]
 func g[T any](I1[T]) {}
 func _() {
 	g(V1)
-	g(V2 /* ERROR "type I2[int] of V2 does not match inferred type I1[int] for I1[T]" */)
+	g(V2)
 }