-- Mathlib/Topology/Category/CompHausLike/Limits.lean
lemma pullback.hom_ext {Z : CompHausLike P} (a b : Z ⟶ pullback f g)
    (hfst : a ≫ pullback.fst f g = b ≫ pullback.fst f g)
    (hsnd : a ≫ pullback.snd f g = b ≫ pullback.snd f g) : a = b

Proof state:
case h.h.a.fst
P : TopCat → Prop
X Y B : CompHausLike P
f : X ⟶ B
g : Y ⟶ B
inst✝ : HasExplicitPullback f g
Z : CompHausLike P
a b : Z ⟶ pullback f g
z : ↑Z.toTop
hfst : (ConcreteCategory.hom (a ≫ fst f g)) z = (ConcreteCategory.hom (b ≫ fst f g)) z
hsnd : (ConcreteCategory.hom (a ≫ snd f g)) z = (ConcreteCategory.hom (b ≫ snd f g)) z
⊢ (↑((ConcreteCategory.hom a) z)).1 = (↑((ConcreteCategory.hom b) z)).1

Tactic:
exact hfst

Result:
no goals

Proof state:
case h.h
P : TopCat → Prop
X Y B : CompHausLike P
f : X ⟶ B
g : Y ⟶ B
inst✝ : HasExplicitPullback f g
Z : CompHausLike P
a b : Z ⟶ pullback f g
hfst : a ≫ fst f g = b ≫ fst f g
hsnd : a ≫ snd f g = b ≫ snd f g
z : ↑Z.toTop
⊢ (ConcreteCategory.hom a) z = (ConcreteCategory.hom b) z

Tactic:
apply_fun (fun q ↦ q z) at hfst hsnd

Result:
case h.h
P : TopCat → Prop
X Y B : CompHausLike P
f : X ⟶ B
g : Y ⟶ B
inst✝ : HasExplicitPullback f g
Z : CompHausLike P
a b : Z ⟶ pullback f g
z : ↑Z.toTop
hfst : (ConcreteCategory.hom (a ≫ fst f g)) z = (ConcreteCategory.hom (b ≫ fst f g)) z
hsnd : (ConcreteCategory.hom (a ≫ snd f g)) z = (ConcreteCategory.hom (b ≫ snd f g)) z
⊢ (ConcreteCategory.hom a) z = (ConcreteCategory.hom b) z

Proof state:
case h.h
P : TopCat → Prop
X Y B : CompHausLike P
f : X ⟶ B
g : Y ⟶ B
inst✝ : HasExplicitPullback f g
Z : CompHausLike P
a b : Z ⟶ pullback f g
z : ↑Z.toTop
hfst : (ConcreteCategory.hom (a ≫ fst f g)) z = (ConcreteCategory.hom (b ≫ fst f g)) z
hsnd : (ConcreteCategory.hom (a ≫ snd f g)) z = (ConcreteCategory.hom (b ≫ snd f g)) z
⊢ (ConcreteCategory.hom a) z = (ConcreteCategory.hom b) z

Tactic:
apply Subtype.ext

Result:
case h.h.a
P : TopCat → Prop
X Y B : CompHausLike P
f : X ⟶ B
g : Y ⟶ B
inst✝ : HasExplicitPullback f g
Z : CompHausLike P
a b : Z ⟶ pullback f g
z : ↑Z.toTop
hfst : (ConcreteCategory.hom (a ≫ fst f g)) z = (ConcreteCategory.hom (b ≫ fst f g)) z
hsnd : (ConcreteCategory.hom (a ≫ snd f g)) z = (ConcreteCategory.hom (b ≫ snd f g)) z
⊢ ↑((ConcreteCategory.hom a) z) = ↑((ConcreteCategory.hom b) z)

Proof state:
case h.h.a.snd
P : TopCat → Prop
X Y B : CompHausLike P
f : X ⟶ B
g : Y ⟶ B
inst✝ : HasExplicitPullback f g
Z : CompHausLike P
a b : Z ⟶ pullback f g
z : ↑Z.toTop
hfst : (ConcreteCategory.hom (a ≫ fst f g)) z = (ConcreteCategory.hom (b ≫ fst f g)) z
hsnd : (ConcreteCategory.hom (a ≫ snd f g)) z = (ConcreteCategory.hom (b ≫ snd f g)) z
⊢ (↑((ConcreteCategory.hom a) z)).2 = (↑((ConcreteCategory.hom b) z)).2

Tactic:
exact hsnd

Result:
no goals

Proof state:
case h.h.a
P : TopCat → Prop
X Y B : CompHausLike P
f : X ⟶ B
g : Y ⟶ B
inst✝ : HasExplicitPullback f g
Z : CompHausLike P
a b : Z ⟶ pullback f g
z : ↑Z.toTop
hfst : (ConcreteCategory.hom (a ≫ fst f g)) z = (ConcreteCategory.hom (b ≫ fst f g)) z
hsnd : (ConcreteCategory.hom (a ≫ snd f g)) z = (ConcreteCategory.hom (b ≫ snd f g)) z
⊢ ↑((ConcreteCategory.hom a) z) = ↑((ConcreteCategory.hom b) z)

Tactic:
apply Prod.ext

Result:
case h.h.a.fst
P : TopCat → Prop
X Y B : CompHausLike P
f : X ⟶ B
g : Y ⟶ B
inst✝ : HasExplicitPullback f g
Z : CompHausLike P
a b : Z ⟶ pullback f g
z : ↑Z.toTop
hfst : (ConcreteCategory.hom (a ≫ fst f g)) z = (ConcreteCategory.hom (b ≫ fst f g)) z
hsnd : (ConcreteCategory.hom (a ≫ snd f g)) z = (ConcreteCategory.hom (b ≫ snd f g)) z
⊢ (↑((ConcreteCategory.hom a) z)).1 = (↑((ConcreteCategory.hom b) z)).1

case h.h.a.snd
P : TopCat → Prop
X Y B : CompHausLike P
f : X ⟶ B
g : Y ⟶ B
inst✝ : HasExplicitPullback f g
Z : CompHausLike P
a b : Z ⟶ pullback f g
z : ↑Z.toTop
hfst : (ConcreteCategory.hom (a ≫ fst f g)) z = (ConcreteCategory.hom (b ≫ fst f g)) z
hsnd : (ConcreteCategory.hom (a ≫ snd f g)) z = (ConcreteCategory.hom (b ≫ snd f g)) z
⊢ (↑((ConcreteCategory.hom a) z)).2 = (↑((ConcreteCategory.hom b) z)).2

Proof state:
P : TopCat → Prop
X Y B : CompHausLike P
f : X ⟶ B
g : Y ⟶ B
inst✝ : HasExplicitPullback f g
Z : CompHausLike P
a b : Z ⟶ pullback f g
hfst : a ≫ fst f g = b ≫ fst f g
hsnd : a ≫ snd f g = b ≫ snd f g
⊢ a = b

Tactic:
ext z

Result:
case h.h
P : TopCat → Prop
X Y B : CompHausLike P
f : X ⟶ B
g : Y ⟶ B
inst✝ : HasExplicitPullback f g
Z : CompHausLike P
a b : Z ⟶ pullback f g
hfst : a ≫ fst f g = b ≫ fst f g
hsnd : a ≫ snd f g = b ≫ snd f g
z : ↑Z.toTop
⊢ (ConcreteCategory.hom a) z = (ConcreteCategory.hom b) z