go/doc: remove brackets from receiver in example identifier

When constructing a string for a method that will match an example
function's name, remove brackets from the receiver. This makes it
possible to write an example associated with a method of a generic
type.

Also, modify the test for classifying examples to check that all the
expected examples actually appear.

Fixes #52496.

Change-Id: Iebc5768f6cb91df9671dd701b97958fb8081f986
Reviewed-on: https://go-review.googlesource.com/c/go/+/401761
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Jonathan Amsterdam <[email protected]>
Reviewed-by: Robert Findley <[email protected]>

Author: jba

src/go/doc/example.go

@@ -512,7 +512,6 @@ func classifyExamples(p *Package, examples []*Example) {
 	if len(examples) == 0 {
 		return
 	}
-
 	// Mapping of names for funcs, types, and methods to the example listing.
 	ids := make(map[string]*[]*Example)
 	ids[""] = &p.Examples // package-level examples have an empty name
@@ -537,7 +536,7 @@ func classifyExamples(p *Package, examples []*Example) {
 			if !token.IsExported(m.Name) {
 				continue
 			}
-			ids[strings.TrimPrefix(m.Recv, "*")+"_"+m.Name] = &m.Examples
+			ids[strings.TrimPrefix(nameWithoutInst(m.Recv), "*")+"_"+m.Name] = &m.Examples
 		}
 	}
 
@@ -572,6 +571,24 @@ func classifyExamples(p *Package, examples []*Example) {
 	}
 }
 
+// nameWithoutInst returns name if name has no brackets. If name contains
+// brackets, then it returns name with all the contents between (and including)
+// the outermost left and right bracket removed.
+//
+// Adapted from debug/gosym/symtab.go:Sym.nameWithoutInst.
+func nameWithoutInst(name string) string {
+	start := strings.Index(name, "[")
+	if start < 0 {
+		return name
+	}
+	end := strings.LastIndex(name, "]")
+	if end < 0 {
+		// Malformed name, should contain closing bracket too.
+		return name
+	}
+	return name[0:start] + name[end+1:]
+}
+
 // splitExampleName attempts to split example name s at index i,
 // and reports if that produces a valid split. The suffix may be
 // absent. Otherwise, it must start with a lower-case letter and

src/go/doc/example_test.go

@@ -617,6 +617,12 @@ type (
 )
 
 func (Conflict) Conflict() {}
+
+func GFunc[T any]() {}
+
+type GType[T any] int
+
+func (GType[T]) M() {}
 `
 	const test = `
 package p_test
@@ -676,6 +682,12 @@ func ExampleConflict_Conflict()        {} // ambiguous with either Conflict or C
 func ExampleConflict_conflict()        {} // ambiguous with either Conflict or Conflict_conflict type
 func ExampleConflict_Conflict_suffix() {} // ambiguous with either Conflict or Conflict_Conflict type
 func ExampleConflict_conflict_suffix() {} // ambiguous with either Conflict or Conflict_conflict type
+
+func ExampleGFunc() {}
+func ExampleGFunc_suffix() {}
+
+func ExampleGType_M() {}
+func ExampleGType_M_suffix() {}
 `
 
 	// Parse literal source code as a *doc.Package.
@@ -725,12 +737,19 @@ func ExampleConflict_conflict_suffix() {} // ambiguous with either Conflict or C
 		// These are implementation dependent due to the ambiguous parsing.
 		"Conflict_Conflict": {"", "suffix"},
 		"Conflict_conflict": {"", "suffix"},
+
+		"GFunc":   {"", "suffix"},
+		"GType.M": {"", "suffix"},
 	}
 
 	for id := range got {
 		if !reflect.DeepEqual(got[id], want[id]) {
 			t.Errorf("classification mismatch for %q:\ngot  %q\nwant %q", id, got[id], want[id])
 		}
+		delete(want, id)
+	}
+	if len(want) > 0 {
+		t.Errorf("did not find:\n%q", want)
 	}
 }