3367475e83
To infer type arguments in an assignment of the form
var target func(t1, t2, ...) = g
where g is a generic function
func g[P1, P2, ...](p1, p2, ...)
the type checker used the synthetic function call
g(t1, t2, ...)
But because each argument (of type) t1, t2, ... is assigned to its
corresponding parameter p1, p2, ..., type inference uses assignment
rules ("inexact match") for unification.
As a result, types such as mystring and string match even though
they should not (they are not identical), yet function parameter
types must be identical to match.
This CL fixes this by constructing the synthetic call
g'(func(t1, t2, ...))
where g' is the generic function
func g'[P1, P2, ...](func(p1, p2, ...))
This mimics the function assignment directly by representing it as
a single argument passing (of a function-typed argument). Function
parameter types must now be identical to unify.
As an added benefit, the implementation is simpler.
As a consequence, when such an assignment is invalid because the
function types cannot possibly match, we now correctly get an
inference error. Without this change, in some cases unification
would succeed, only to lead to an assignment error afterwards.
While at it, update the date in the copyright notice of
testdata/manual.go so we don't need to fix it each time we copy
code from a test case in manual.go into a issueXXXXX.go file.
Fixes #60688.
Change-Id: I716247f426ef33d76c7849b0c33c59124e55b859
Reviewed-on: https://go-review.googlesource.com/c/go/+/501938
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
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| CONTRIBUTING.md | ||
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| README.md | ||
| SECURITY.md | ||
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